MIMU22BL Integration Guide Revision 1. 12 ±Integration Guide Doc: MIMU22BL-integration-guide.pdf Revision: 1.12 Release Date: 02 May, 2019 w w w . in e r t ia le le m e n t s . c

MIMU22BL–Integration Guide

Doc: MIMU22BL-integration-guide.pdf

Revision: 1.12

Release Date: 02 May, 2019

w w w . i n e r t i a l e l e m e n t s . c o m i n f o @ i n e r t i a l e l e m e n t s . c o m

Page 1

MIMU22BL

Integration Guide

Revision 1.12

© 2019, GT Silicon Pvt Ltd, Kanpur, India

Tel: +91-700-741-0690

Email: [email protected]

URL: www.inertialelements.com

www.gt-silicon.com

Registered Office:

GT Silicon Pvt Ltd

LIG 1398, Avas Vikas 3,

PO NSI, Kalyanpur

Kanpur (UP), India, PIN – 208017



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Revision History

Revision Revision Date Updates

1.0 06 January 2018 Initial version

1.1 23 January 2018 Minor typographical corrections

1.2 2February 2018 Few commands updated

1.3 5February 2018 This integration document is for firmware version 1.2 where the

sampling frequency is changed from 200 Hz to 250 Hz and the heading

is being calculated based on Magnetometer of IMU # 3 instead of fused

Magnetometer data.

1.4 22 March 2018 Change the command for “High precision IMU with Pressure and

Magnetometer #3 data” to avoid complexity. This is an alternate

command and also backward compatible. Upgraded Output mode

Sample table andminor typographical corrections

1.5 15June 2018 Change in the “Output Osmium Data” data format.

1.6 21 June 2018 Few typographical corrections

1.7 18July 2018 Few minor changes and typographical corrections

1.8

08 Aug 2018 Included USB driver installation

Modified hexadecimal number representation (0x)

Checksum computation explained in Appendix IV (1)

Command’s acknowledgement packet explained in Appendix IV(2)

1.9 11 Aug 2018 Added figures for board features and IMU orientations.

1.10 14 Aug 2018 Included feature list

Included examples of converting hex values to actual values



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1.11 22 Aug 2018 Few minor changes

1.12 02 May 2019 Explanation of timestamp



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Purpose & Scope

This document describes the data processing flow in MIMU22BL. It also describes communication

protocol using which one can access and control the data and the processing at various stages, through an

external application platform.

Please refer following documents also for specific details:

1. Datasheet –ICM-20948

2. 32-bit AVR Microcontorller Specification

https://www.invensense.com/wp-content/uploads/2016/06/DS-000189-ICM-20948-v1.3.pdf

http://www.inertialelements.com/oblu/resources/AVR32UC3C.pdf



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Introduction

MIMU22BL is a multi-IMU based inertial navigation module. MIMU22BL, with on-board four 9-DOF

IMUs, is targeted towards foot mounted pedestrian application and can also be use as a development

platform for carrying out research in motion sensing, robotics, IoT etc.

MIMU22BL has a wireless interface (BLE 4.1) for data transfer. Due to on-board 32-bits floating point

controller, device has a simplified dead reckoning interface (for foot-mounted application). An

application platform receives a stream of displacement and heading changes (displacement vector), which

it sums up to track the current position of wearer. This is a significant simplification compared with

handling and processing high-rate raw inertial measurements. There is also option of using on-board

micro-USB connector for USB data transfer. Same port is used for battery charging.

MIMU22BL can also be used as a normal / precision wireless IMU for other non foot mounted

applications such as robotics, VR/AR etc. In summary, presence of on-board 32-bits floating point

controller enables on-board computing and hence simplified output data format, with significantly

reduced data transfer rate. And this also results in lesser computation overhead for the receiving

(attached) device and superior tracking results. [1]

Fig. 1: Tracking with foot-mountedMIMU22BL and data collection using BLE 4.1

MIMU22BL

MIMU22BL

This document describes the data processing flow

in MIMU22BL. It also describes communication

protocol using which one can access and control

the data and the processing at various stages,

through an external application platform.

[1] John-Olof Nilsson, Amit K Gupta, Peter

Handel, "Foot mounted inertial navigation made easy",

InProc Indoor Positioning & Indoor Navigation

(IPIN), Busan, Korea, 2014.



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Highlighting Features

4 nine-axis IMU array (Accelero+Gyro+Magnetometers)

IMUs’ placement and orientation to minimize systematic errors

Bluetooth v4.1 and USB 2.0 data interfaces

32b Floating point controller with 512 Kb internal flash

Pressure Sensor, 8 Mb DataFlash memory*

Barometer & IMU fused altimeter for superior altitude performance

Inbuilt sensor fusion and calibration compensation

Power with Li-ion battery, USB; Battery charging with USB

ON-OFF switch, LED indicators; Peak continuous current: 65mA

Onboard connector for programming

USB (Bootloader) programmable; JTAG programmable

Single board; Low profile

Rechargeable battery; Battery backup:

MIMU22BLPX : Eight to Nine hours

MIMU22BLP : Two and a half hours approx

Dimensions & Weight:

o MIMU22BL : 20.9x22.7x5.0 mm; Weight - 3.5 g

o MIMU22BLPX : 42.2 x 27.9 x 17.0 mm; 20gm

o MIMU22BLP : 31.0 x 23.5 x 13.5 mm; 12gm

*Contact us forfirmware support for DataFlash memory.



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Dimensions:



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IMUs’ Orientation

Figure 3 IMUs’ orientation as appears from the top side of the board. IMUs on top and bottom are exactly mirrored. This means that the “dot” indication marks of the top and bottom IMUs are aligned. IMUs are numbered from 1 to 4.



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USB Driver Installation

One must install USB driver for data communication with PC (or any data acquisition system).

The on-board microcontroller Atmel AT32UC3C0512C offers USB 2.0 port. The USB connector on

MIMU22BL board is directly connected with the USB pins of the controller.

The USB port of the microcontroller has been programmed in the firmware as CDC Virtual COM, so that

it appears as a UART port (COM port) when connected with a PC. Hence installation of a corresponding

USB driver on PC (or data acquisition system) is required, if the board has to communicate with the PC

through its USB port.

(i) Download the Atmel USB driver file and its installation manual from

https://www.inertialelements.com/resources.html.

(ii) Go to Computer management/Device Manager/Port and update the driver as instructed in the

manual. Though the installation process is demonstrated for Windows 10, it is same for the

previous versions of Windows OS.

For video demo, please visit the support page from www.inertialelements.com and check the video with

title “How to update USB Driver for MIMU22BL”

https://www.inertialelements.com/resources.html

http://www.inertialelements.com/



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Data Flow

Sensors’ raw data from IMU is read in parallel by the microcontroller through I2C buses realized in

software. The sensors’ data is calibration compensated and fused (averaged) to get single ax, ay, az, gx, gy

and gz. ZUPT aided inertial navigation is implemented, which generates displacement and heading change

data.

Error

Covariance

Orientation

(Heading

change, dθ)

Displacement

(dx, dy, dz)

g’x,g’y, g’z

a’x, a’y, a’z

gx1, gy1, gz1

ax1, ay1, az1

IMU#1

gx2, gy2, gz2

ax2, ay2, az2

IMU#2

gx3, gy3, gz3

ax3, ay3, az3

IMU#3

gx4, gy4, gz4

ax4, ay4, az4

IMU#4

Sensor

Fusion

&

Calibration

Compensation

ZUPT-aided

Inertial

Navigation

MIMU22BL µ-Controller

or /

&

Figure 4 Illustration of data flow sequence in MIMU22BL with ZUPT-aided inertial navigation.



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Communication Protocol

The interfacing application platform (Computer, Phone, Tab etc) sends a particular command (data

request) to MIMU22BLwho serves the request by sending out required data to the application platform.

Each command calls a particular state, which can send out variety of data depending upon command

options.

Command format = [header,{payloads}, checksum*]

Header is of 4-bytes.Payload contains the main data. Its size and content would change from one

command to other.Checksum is of two bytes (cs1, cs2). Last two bytes in any command are

checksum.

Refer Appendix IV for header format and checksum computation.

All the commands described in this document, are represented in decimal format unless otherwise

specified.

MIMU22BL transmits 4 bytes acknowledgement (ACK) in response to command from the

application platform. MIMU22BL always sends an ACK to the command, before sending

corresponding output data packet(s).

Refer Appendix IV(2) for the format of ACK packet.

Figure 5 Data communication protocol between MIMU22BL and the application platform

COMMANDi

oblu

(As Slave) Application Platform

(As Master)

Command1

Command2

Command3

Command4

Command5

DATAi

State1 State2 State3 State4 State5

Data1 Data2 Data3 Data4 Data5

MIMU22BL



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All the outputs from MIMU22BL are in big – endian format. Those are represented in hex format

in this document.

Table 1: Summary of some useful commands

Sl. No.

Command Description Syntax (in decimal)

1 Stepwise Dead Reckoning (PDR)

MIMU22BL outputs displacement (dx, dy, dz) &

change in orientation (dθ) w.r.t the previous detected step and

entries of a 4x4 symmetric covariance matrix

[52 0 52]

cs1 = 0 cs2 = 52

2 Barometer Fused Altimeter This is the height as obtained

from the device by fusing barometer with IMUs.

[69 pl1 cs1 cs2] pl1 is the output rate divider

3 Processing off

MIMU22BL (controller) switches off all the processing.

It makes the processing sequence empty

[50 0 50] cs1 = 0

cs2 = 50

4 All output off

MIMU22BL turns off output of all the states and stops transmitting data to the

application platform

[34 0 34] cs1 = 0

cs2 = 34

5 Read inertial data MIMU22BL starts sampling

onboardIMUs’ (acceleros’ and gyros’ data)

[48 19 0 0 67] cs1 = 0

cs2 = 67

6 Output inertial data

MIMU22BL transmitting the inertial sensors’ raw data axi,

ayi, azi, gxi, gyi, gzi of the selected IMUi, to the application platform.

[40 pl1 pl2 pl3 pl4 pl5 cs1 cs2]

pl1, pl2, pl3, pl4 all together consists

of 32bits. Each bit corresponds to particular IMU. Thus pl1-pl4 is used to select IMUs.** pl5 is the output

mode*. cs1, cs2: checksum

7 Read magnetometer data MIMU22BL starts sampling and

calibrating onboard IMUs’ magnetometer data

[48 20 0 0 68] cs1 = 0

cs2 = 68

8 Read pressure data MIMU22BL starts sampling

onboard Pressure sensor’s data

[48 21 0 0 69] cs1 = 0

cs2 = 69

9 Read Inertial and Magnetometer

data

MIMU22BL starts sampling onboard IMUs’ calibrated

magnetometer and Inertial data simultaneously

[48 24 0 0 72] cs1 = 0

cs2 = 72

10 Read Osmium Data

MIMU22BL starts sampling onboardIMUs ‘calibrated

magnetometer and Inertial as well as pressure sensor data

simultaneously

[48 22 0 0 70] cs1 = 0

cs2 = 70

11 Output Osmium Data MIMU22BL transmitting the inertial sensors’ raw data axi,

[43 pl1 pl2 pl3 pl4pl5 cs1 cs2] pl1, pl2, pl3, pl4 all together consists



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ayi, azi, gxi, gyi, gzi, magnetometer raw data mxi,

myi, mzi and temperature data of the selected IMUs and

Pressure and temperature data from Pressure sensor to the

application platform.

of 32bits. Each bit corresponds to particular IMU. Thus pl1-pl4 is used to select IMUs.** pl5 is the output

mode*. cs1, cs2: checksum

12 Read IMU temperature data MIMU22BL starts reading internal temperature of the

onboard IMUs’

[53 0 53] cs1 = 0

cs2 = 53

13 Output IMU temperature data

MIMU22BL starts transmitting temperature of the selected

onboard IMU(s), to the application platform.

[40 pl1 pl2 pl3 pl4 pl5 cs1 cs2]

pl1, pl2, pl3 and pl4 are same as in

the command for state OUTPUT_IMU_RD**. pl5 is the

output mode* byte, cs1, cs2: checksum

14 High precision IMU (Normal

IMU)

MIMU22BL outputs g’x, g’y, g’z, a’x, a’y, a’z (ref Fig 2 and

Fig 3) after calibration compensation and sensor fusion.

[64 pl1 cs1 cs2] pl1 = output mode* cs1, cs2: checksum

15 High precision IMU with bias

estimation

MIMU22BL outputs g’x, g’y, g’z, a’x, a’y, a’z after

calibration compensation and sensor fusion along with the

estimated bias.

[65 pl1 cs1 cs2] pl1 = output mode* cs1, cs2: checksum

16 High precision IMU

withMagnetometer #3 data


Fig 3) after calibration compensation and sensor fusion

along with calibratedMagnetometer #3 data

(m’x, m’y,m’z)

57 pl1 cs1 cs2 pl1 is the output mask mode$, cs1,

cs2: checksum

17 High precision IMU with Pressure

data



along with pressure data.

57 pl1 cs1 cs2 pl1 is the output mask mode*, cs1,

cs2: checksum

18 Output High precision IMU with Pressure andMagnetometer #3

data



along with calibratedMagnetometer #3 data

(m’x, m’y,m’z) and pressure data.

[49 22 16 00 00 00 00 00 00 00 87] [33 08 13 52 187 00 00 00 00 pl2 cs1

cs2]

pl2 = output mode* cs1, cs2: checksum

19 Request output of state Requests the state connected to

the state ID to be output.

[32 pl1 pl2 cs1 cs2] pl1 = state ID

pl2 = output mode* cs1, cs2: checksum

20 Request output of multiple states Requests the multiple states

connected to the state IDs to be output.

[33 pl1 pl2 pl3 pl4 pl5 pl6 pl7 pl8 pl9 cs1 cs2]

pl1-pl8 = state ID pl9 = output mode*



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cs1, cs2: checksum

21 Set the gravity value Set acc. due to gravity “g” value [6 g0 g1 g2 g3 g4 g5 g6 cs1 cs2]

g0 to g6 = g value cs1, cs2: checksum

22 Calibration data values set Input calibration data of

MIMU22BL

[36 pl1 pl2 pl3 pl4 pl5 pl6 pl7 pl8 pl9 pl10 pl11 pl12 pl13 pl14 pl15 pl16

pl17 pl18 pl19 cs1 cs2] pl1 = select IMU position

pl2 – pl19 = 4 byte calibration data cs1, cs2: checksum

23

Calibration F- bias set Input fused accelerometer bias [8 pl1 pl2 pl3 cs1 cs2]

pl1 – pl3 = 4 byte each input data cs1, cs2: checksum

24 Calibration G- bias set

Input fused gyroscope bias [9 pl1 pl2 pl3 cs1 cs2]

pl1 – pl3 = 4 byte each input data cs1, cs2: checksum

25 Set calibration F & G bias Input the bias estimation value

of individual IMU’s accelerometer and gyroscope

[37 pl1 pl2 pl3 pl4 pl5 pl6 pl7 cs1 cs2]

pl1 = select IMU position pl2 – pl7 = 4 byte each data

cs1, cs2: checksum

26 Set FG scale Select the Accelerometer and

gyroscope scale

[68 pl1 pl2 cs1 cs2] pl1= fs_scale

pl2 = afs_scale cs1, cs2: checksum

27 Set IMUs Select the number of IMUs [7 pl1 cs1 cs2]

pl1= select IMUs position cs1, cs2: checksum

28 Flog set IMU Log2(No. of IMUs) [5 pl1 cs1 cs2]

pl1= select # of IMUs position cs1, cs2: checksum

29 Software Version Version of the Firmware by

which MIMU22BL is programmed

[41 cs1 cs2] cs1, cs2: checksum

30 Get Device ID ID of the device [25 cs1 cs2]

cs1, cs2: checksum

31 Stepwise Dead Reckoning with

true compass heading

MIMU22BL outputs tilt compensated compass heading,

displacement (dx, dy, dz) & change in orientation (dθ) w.r.t the previous detected step and

entries of a 4x4 symmetric covariance matrix

[67 64 01 31]

32 Output Raw IMU+ Magneto Data

MIMU22BL transmitting the inertial sensors’ raw data axi,

ayi, azi, gxi, gyi, gzi, magnetometer calibrated data

mxi, myi, mzi

[33 57 58 59 60 185 186 187 188 rd cs1 cs2]

*Output mode (MODE): Its 1 byte output mode.

MODE[3:0] - Output rate divider# (0x0 to 0x0f).

MODE[4] - 1: Lossless transmission# of output data packet.



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0: Not a lossless transmission of output data packet. (Recommended for Precision IMU mode)

MODE[5] - This bit is meaningful only if output rate divider$ (RD) is set to 0.

1: MIMU22BL generates only a single output data packet in response to a command

0: MIMU22BL does not generate any output data packet.

MODE[6] – 1: Output contains raw data of each IMU, i.e. acc and gyro data from each sensor

0: Raw IMU data disabled

MODE[7] – 1: Temperature data of all the 32 IMUs

0: Temperature data disabled

Table 2: Output mode Sample

Output mode

(Binary Bits)

Rate

divider

MODE[3:0]

Lossless*1

MODE[4]

Single time

output

MODE[5]

Raw IMU

MODE[6]

Raw IMU

Temperature

MODE[7]

Other

Output*1

Decimal

Equivalent

0000 0001 -

0000 1111 1-15 X X X X ✓

1-15

0100 0001 –

0100 1111 1-15 X X ✓ X X

65-79

0101 0001 –

0101 1111 1-15 ✓ X ✓ X X

81-95

1001 0001 –

1001 1111 1-15 ✓ X X ✓ X

145-159

1000 0001-

1000 1111 1-15 X X X ✓ X

129-143

0110 0000 0 X ✓ ✓ X X 96

00010001-

00011111 1-15 ✓ X X X ✓

17-31

00100000 0 X ✓ X X ✓ 32

00110000

(No use) 0 ✓ ✓ X X ✓

48

*1: For lossless transmission, each data packet must be acknowledged by the application platform. In this

mode, MIMU22BL transmits next data packet, only on receiving acknowledgement for the previous one.

The data acknowledgement (“PKG ACK”) packet is different from command acknowledgement (ACK

received in response to command). Refer Appendix II(4) for details about PKG ACK.

*2: Other output includes all data output commands where output mode is used except “Output inertial

data” and “Output IMU temperature data”.



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$Output Mask Mode: This is basically same as Output Mode but we have added some extra mask for

procuring data

MM[3:0] - Output rate divider$ (0x0 to 0x0f).

MM[4] - 1: Lossless transmission## of output data packet.

0: Lossy transmission of output data packet. (Recommended for Precision IMU mode)

MM[5] - This bit is meaningful only if Output rate divider$ (RD) is set to 0.

1: MIMU22BL generates only a single output data packet in response to a command.

0: MIMU22BL does not generate any output data packet.

MM[7:6] - These bits select combination of the sensors’ data in output packet.

01: Packet contains data for 3-axis accelerometer, 3-axis gyroscope and 3-axis magnetometer

10: Packet contains data for 3-axis accelerometer, 3-axis gyroscope and pressure sensor

00: Packet contains data for 3-axis accelerometer and 3-axis gyroscope

11: RESERVED

##For lossless transmission, each data packet must be acknowledged by the application platform. In this

mode, MIMU22BL transmits next data packet, only on receiving acknowledgement for the previous one.

The data acknowledgement (“PKG ACK”) packet is different from command acknowledgement (ACK

received in response to command). Refer Appendix IV(4) for details about PKG ACK.

Table 3: Output Mask mode

Output mode

(Binary Bits)

Rate

divider

Lossless Single

time

output

Acc + Gyro

+ Mag

(Fused)

(0x40)

Acc + Gyro

+ Pressure

(0x80)

Decimal

Equivalent

0000 0000 -

0000 1111 1-15 X X X X

1-15

0100 0001 –

0100 1111 1-15 X X ✓ X

65-79

0101 0001 –

0101 1111 1-15 ✓ X ✓ X

81-95

1001 0001 –

1001 1111 1-15 ✓ X X ✓

145-159



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1000 0001-

1000 1111 1-15 X X X ✓

129-143

0110 0000 0 X ✓ ✓ X

96

0110 0001-

0110 1111 1-15 X X X X

97-111

0111 0001-

0111 1111 1-15 ✓ X X X

113-127

Output Rate Divider (RD): It consists of only one byte. It manipulates the rate of output of the particular

state asked in this command. If sensors’ data read rate is ‘f’, then the output data rate of this particular

state will be f/ (2^ (pl2-1)). The largest value of pl2 can be 15. Thus if pl2=1 (smallest value), then the

particular state will be output for every data read from sensors. [Assuming that pl2 is the single byte RD.]

In very simple words, RD decides the rate of data transmission from MIMU22BL to the application

platform. The maximum transmission rate is 250 Hz which is same as the inertial sensors’ sampling

frequency. Transmission rates for the RD upto 7 are given in the following table:

Output Rate Divider

Data Transmission Rate (Hz)

1 250

2 125

3 62.5

4 31.25

5 15.625

6 7.8125

7 3.90

Please refer Appendix I for detailed description of Commands and States.

**Selection of IMUs: 4 byte payloads pl1-pl4 consists of 32 bits.

pl1[7:0] – 0x0

pl2[7:0] – 0x0

pl3[7:0] – 0x0

pl4[7:4] – 0x0

pl4[3:0] – Here each bit corresponds to an IMU. For output of raw data from any combinations of IMUs,

set the bit corresponding to that IMU. Refer Table 4 for all possible combination of selection of IMUs.



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Table 4: Selection of IMUs

Selection Bit

pl4[3:0]

pl[3]

(IMU3)

pl[2]

(IMU2)

pl[1]

(IMU1)

pl[0]

(IMU0)

Decimal

Equivalent

All 4 IMUs selected 1

1

1

1

0 0 0 15

Combination for 3

IMUs

1 0 1

1

0 0 0 11

1 1 0 1

0 0 0 13

1 1 1

0 0 0 0 14

0 1 1

1

0 0 0 7

Combination for 2

IMUs

0 0 1

1

0 0 0 3

0 1 0 1

0 0 0 5

1 0 0 1

0 0 0 9

1 1 0 0 0 0 0 12

1 0 1 0 0 0 0 10

0 1 1 0 0 0 0 6

Combinations for

single IMU

0 0 0 1

0 0 0 1

0 0 1 0 0 0 0 2

0 1 0 0 0 0 0 4

1 0 0 0 0 0 0 8



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Stepwise Dead Reckoning with Android Application Platform

As an example, we consider a specific case of using MIMU22BL for stepwise dead reckoning with an

(Android) application platform, communicating wirelessly. Refer Application Note on Stepwise Dead

Reckoning for detailed description.

Command for Stepwise

Dead reckoning data X

Y

Z

dx

dy

dz Summation

&

Heading

MIMU22BL

(Pedestrian Dead

Reckoning Platform)

Sensor Fusion

(Displacement &

Heading change sensor)

Calibration

Compensation

ZUPT-aided

Inertial Navigation

Multiple-IMUs

Sensing

Displacement (dx, dy, dz)

Orientation (Heading change, d)

d

Figure 6Interfacing of MIMU22BL with an application platform

Android Application

Figure. 7: Pedestrian Dead Reckoning (PDR) is simplified with the foot-mounted MIMU22BL. The device starts transmitting

location data at every step, on receiving start command from the application platform.



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The MIMU22BLsends out stepwise dead reckoning data in form of packets via wireless communication,

in response to the command [52 0 52] from application platform.Below figure illustrates how the packets

look like.

Data Packet

These packets consisted of 64 bytes.

1. Header: First 4 bytes are ‘Header’.

a. Among these 4 bytes, first is the header which is STATE_OUTPUT_HEADER which is

170 (0xAA).

b. 2nd and 3rd byte jointly tells the data packet number sent by the device since the beginning

of stepwise dead reckoning. Thus the packet number is a 16-bits variable.

c. 4th byte depicts the payload i.e. the number of bytes (0x3A) this data packet contains

which consists of required information asked by the user.

Refer Appendix IV for better understanding of Header.

2. Payload: Next 56 bytes are payload, which consists of 14 elements of type ‘float’ thus

comprising of 14*4=56 bytes.

a. First 4 elements consists of the displacement vector i.e. the change in position x, y, z and

the angle of rotation around z-axis (the change in the angle of the x-y plane). These

elements follow IEEE 754 4bytes floating point representation. The change in position is

between two successive ZUPT instances, i.e. the displacement vector from one step to the

next one.

B00 B01 B02 B03 B04 B05 B58 B59 B60 B61 B62 B63

Header Payload

Check

sum

B00: State of the Header

B01-B02: Data packet number

B03: Number of bytes in Payload

B04-B07: Displacement in x (Type float)

B08-B11: Displacement in y (Type float)

B12-B15: Displacement in z (Type float)

B16-B19: Change in angle around z axis (Type float)

B20-B59: 10 entries (4 bytes each) of a 4x4

symmetric covariance matrix

B62-B63: Check sum

B60-B61: Step counter

Figure 8Data packet for stepwise dead reckoning



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b. The other 10 elements of the payload are used to form the covariance matrix, which is a

4x4 symmetric matrix, thus 10 elements. These elements denote the estimated error value

for the displacement vector.

3. Step Counter: Next two bytes consists of step counter, which is a counter taking record of ZUPT

instances observed. This is essentially number of times MIMU22BL detects steps, i.e. the

standstill moment in one’s stride. Therefore the step counter is the number of steps detected by

MIMU22BL when used as shoe-mounted PDR sensor for pedestrian tracking.

4. Checksum: The last two bytes of 64 bytes consist of checksum which is sum of all the bytes

received prior to these. These are used to cross-check correctness of the data transferred. Refer

Appendix IV to know more about Checksum.

Rotation in Application Platform

MIMU22BL transmits tracking data with respect to its own frame which itself is not fixed with

respect to the user’s global reference frame. Therefore the data should undergo rotational

transformation before being presented to the end user in a global reference frame. (Here global

refers to the coordinate axis in which the system is initialized.)

The first four bytes of Payload are the position and heading change vector (displacement vector),

i.e. dx, dy, dz, dθ (dθ is the change in angle of rotation about z-axis or yaw). These values are the

output from the device at every ZUPT instance. As mentioned earlier, each set of displacement

vector describes movement between two successive steps. The position and heading change

vector are with reference to the coordinate frame of last ZUPT instance.

The ‘dθ’ corresponds to the deviation in the orientation of MIMU22BL. It is rotation of the x-y

plane about the z-axis, and z-axis is always aligned with the gravity. The data is thus used for

updating the orientation of the system, and obtaining the global reference frame. The two

dimensions of displacement vector (dx, dy) are transformed to the global frame by applying

rotation and thus (x,y) in the global frame is obtained. As we do not consider any change in

alignment in z-axis, updating the z coordinate is performed by simply adding present dz to the z

obtained for previous ZUPT.



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Thus x,y,zcoordinates in the global reference frame are obtained at every ZUPT.

Details are covered in Application Note. You may also refer Appendix II for a piece of an

example Python script for better understanding of implementation.



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Appendix I

1. State: Stepwise Dead Reckoning (SWDR)

Command: [52 0 52]

MIMU22BL sends out data packet for stepwise dead reckoning in response to this command [2].

Use this command only through Bluetooth. It will not work through USB.

2. State: Barometer fused Altimeter (BFA)

Command: [69 pl1 cs1 cs2]

This is the height as obtained from the device by fusing barometer with IMUs. In SWDR we

received corrected relative altitude. This command is for relative information based on fused

barometer and IMU data without any correction.

Example Output (USB):

Command: [69 02 00 71] o/p rate:2=125Hz

This is the generated output

0xAA 0x00 0x06 0x08 0x21 0xC4 0x48 0xF7 0x3D 0xB8 0x51 0xEC 0x05 0x0E

Total packet size: 14 bytes (4 bytes Header; 8 bytes payload and 2 bytes checksum)

First 4 bytes (Header): 0xAA 0x00 0x06 0x08 (0xAA - command; 0x00 0x06 - Data packet

number; 0x08 - data packet size)

During SWDR

SWDR altitude

correction Final Relative Altitude

Barometer fused

Altimeter Relative Altitude w/o any correction

During BFA

Figure 6 Flow diagram of altitude from SWDR and BFA



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Next 8 bytes (Payload): First 4 bytes (unsigned integer) of payload are time stamp; Next 4 bytes

are altitude data in float (IEEE 754 floating point representation).

Checksum:0x05 0x0E

3. State: Processing Off

Command: [50 0 50]

MIMU22BL terminates all the ongoing processing in response to this command. This is soft OFF

button. There would not be any output to this command. On giving this command there will be

only a command acknowledgement. This command is recommended as soon as the user finishes

collecting data preceded by (4) i.e All Output Off command.

4. State: All Output Off

Command: [34 0 34]

If this command is passed to the system, then the transmission of data packets would stop. But

there will be no change in the process going on inside, that all the functions would be running as

it is, just the thing is values would not be output. There would not be any output to this command.

On giving this command there will be only a command acknowledgement. This command is also

recommended as soon as the user finishes collecting data followed by (3) i.e “Processing Off”

command.

5. State: Read Inertial Data

Command: [48 19 pl1 cs1 cs2]

This command creates enabling conditions for the command Output Inertial Data, i.e. (6).

Therefore this command must be run just before (6). There would not be any output to this

command. On giving this command there will be only a command acknowledgement.

cs1, cs2: Two bytes checksum

Example:

Recommended for USB:



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[48 19 0 67]

No output for this command.

6. State: Output Inertial Data

Command: [40 pl1 pl2 pl3 pl4 pl5 cs1, cs2]

MIMU22BLoutputs IMU sensors’ readings in response to this command.

Here pl1, pl2, pl3 and pl4 constitute one byte each. These are used for selecting IMUs. Consider

the pl1, pl2, pl3 and pl4 all together constitute 4 bytes i.e. 32 bits, where each bit corresponds to

one of the 32 IMUs.

Consider if we want to select the first 4 IMUs we want to have the 4 LSBs to be 1 which can be

made by having pl4 be 15 (binary: 00001111) and all the others be 0. Thus [40 0 0 0 15 1 0 56] is

a sample command selecting the first four IMUs for getting the raw inertial data. pl5 here is the

output mode byte.

Here the output consists of [axi, ayi, azi, gxi, gyi, gzi] for each IMU selected, as in Fig 2. As each of

the values corresponds to 2 bytes, thus the output is of 12 bytes for each IMU.

Note: (5) i.e. command “Read Inertial Data” command must be run before this command.

Also note that MIMU22BL has only four IMUs. However the s/w can support upto thirty two

IMUs.


Example:

Set of commands to obtain data packets containing 4 accelerometers' and 4 gyroscopes' data:

Recommended for USB:

[48 19 0 67]

[40 0 0 0 15 65 0 120] (o/p data rate:1 = 250 Hz)

Recommended for Bluetooth



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[48 19 0 67]

[40 0 0 0 15 68 0 124] (o/p data rate: 4* = 25 Hz)

*output rate divider is 64+ Output rate divider.

Here are the example data packets containing 4 accelerometers' and 4 gyroscopes' data, obtained

as a result of above set of commands (USB):

0xAA 0x00 0x01 0x34 0x21 0xC4 0x48 0xF7 0x00 0x6E 0x00 0x54 0x07 0x57 0xFF 0xE4 0x00

0x05 0x00 0x17 0xFF 0x98 0xFF 0x81 0xF7 0x6A 0xFF 0xD2 0x00 0x13 0x00 0x11 0x00 0x7E

0x00 0x57 0x07 0xD9 0xFF 0xF6 0x00 0x0B 0xFF 0xEF 0xFF 0x9A 0xFF 0x8C 0xF7 0x60 0xFF

0xF6 0xFF 0xF0 0xFF 0xFC 0x1C 0x8C

0xAA 0x00 0x02 0x34 0x21 0xC5 0x35 0xEC 0x00 0x6E 0x00 0x54 0x07 0x57 0xFF 0xE2 0x00

0x04 0x00 0x16 0xFF 0x90 0xFF 0x7F 0xF7 0x68 0xFF 0xD4 0x00 0x13 0x00 0x11 0x00 0x68

0x00 0x56 0x07 0xD0 0xFF 0xF5 0x00 0x0A 0xFF 0xF0 0xFF 0x8E 0xFF 0x91 0xF7 0x54 0xFF

0xF2 0xFF 0xF2 0xFF 0xFE 0x1C 0x2E

Description of the above packet:

Total packet size: 58 bytes (4 bytes Header + 52 bytes Payload + 2 bytes Checksum)

First 4 bytes (Header): 0xAA 0x00 0x01 0x34 (0xAA - command; 0x00 0x01 - Data packet

number; 0x34 - data packet size). Refer Appendix IV (3) to understand the output header in

details.

Next 52 bytes (Payload): First 4 bytes (unsigned integer) of payload are time stamp; 2 bytes

integer each for ax1, ay1, az1, gx1, gy1, gz1, ax2, ay2, az2, gx2, gy2, gz2, ax3, ay3, az3, gx3, gy3,

gz3, ax4, ay4, az4, gx4, gy4 and gz4

Last 2 bytes (Checksum): 0x1C 0x8C

How to obtain output of sensor in decimal:

Data Data type Scale

(Multiplication factor)

Addition Factor Unit

Acceleration 2 bytes integer

(1/2048.0)*gvalue

[gvalue is 9.79 m/s^2] X

meter per second square (m/s^2)



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Angular rotation speed

2 bytes integer 1/16.4 X degree per second

Timestamp* (5th

to 8th

bytes) - 0x21 0xC4 0x48 0xF7 (4 byte unsigned integer) => 566511863,

multiply by scale factor => 566511863/(16e6) => 35.04 second

ax1 (9th

to 10th

bytes)- 0x00 0x6E (2 byte integer) => 110, multiply by scale facto r=>

110*(1/2048.0)*9.79 => 0.5258 m/s^2

gx1 (15th

to 16th

bytes)- 0xFF 0xE4 (2byte integer) => -28, multiply ye scale factor => -28*

(1/16.4) => -1.7073 degree per second

*As soon as the device is powered on, the system clock starts ticking at the pre-set system clock

frequency, which is 16 MHz for MIMU22BL. The number of ticks is indicated by “timestamp”.

The maximum value of timestamp is 4,294,967,295. It restarts from 0 after attaining this

maximum value during the operation. In order to convert value to seconds, timestamp should be

multiplied by a scale factor of 1/ (System clock frequency). This definition of timestamp is

applicable for other commands as well.

7. State:Read magnetometer data

Command:[48 20 0 cs1 cs2]

This command is used to initiate sampling and calibration of the onboard IMU’s magnetometer

data byMIMU22BL.

rd: Output rate divider


It is recommended to set the rd to default 0. This will sample data at the maximum possible

sampling rate.

8. State: Read Pressure data


This command is used to initiate sampling of the onboard pressure sensor data by MIMU22BL.



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9. State: Read Inertial and Magnetometer data


This command is used to initiate sampling and calibration of the onboard IMU’s magnetometer

and sampling of inertial sensors’ data by MIMU22BL simultaneously.


10. State: Read Osmium Data


This command is used to initiate sampling and calibration of the onboard IMU’s magnetometer,

sampling of inertial sensors’ data and sampling of the onboard pressure sensor data by

MIMU22BL simultaneously.



Table 4: Data access commands for Normal IMU, Magnetometer #3 and pressure sensor

State Command Inerti

al

Magneto Pressure

Read Inertial Data [48 19 0 0 67] ✓ X X

Read magnetometer data [48 20 0 0 68] X ✓ X

Read Pressure data [48 21 0 0 69] X X ✓

Read Inertial and

Magnetometer data

[48 24 0 0 72] ✓ ✓ X

Read Osmium Data [48 22 0 0 70] ✓ ✓ ✓



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11. State: Output Osmium Data

Command:[43 pl1 pl2 pl3 pl4 rd cs1 cs2]

MIMU22BL transmitting the inertial sensors’ raw data axi, ayi, azi, gxi, gyi, gzi, magnetometer

raw data mxi, myi, mzi and temperature data of the selected IMUs and Pressure and temperature

data from Pressure sensor to the application platform.

pl1 pl2 pl3 pl4 – These payloads is for selection of IMUs.

rd- Output rate divider

cs1 cs2- Check Sum.

Example:

Set of commands to obtain data packets containing 4 accelerometers' and 4 gyroscopes' data, 4

magnetometers, 1 pressure sensor data, 4 sets of temperature from 4 IMUs, 1 set of temperature

from pressure sensor.

Example for USB

[48 22 al cs1 cs2]

[43 pl1 pl2 pl3 pl4 rd cs1 cs2]

al ->array location. Set it as 0 to run a single processing function.

Data packets received from USB:

0xAA 0x04 0xF6 0x7E 0xB6 0x77 0x68 0x0D 0x00 0x3F 0x28 0xE70xE70x43 0xFF 0xFE 0xFF

0x48 0x07 0xB0 0xFF 0xED 0x00 0x03 0x00 0x03 0x00 0x39 0xFF 0x60 0x08 0x10 0x00 0x0C

0xFF 0xFF 0x00 0x08 0xFF 0xE4 0xFF 0x3A 0x07 0xD1 0x00 0x13 0xFF 0xDC 0x00 0x0F 0x00

0x0A 0xFF 0x31 0x07 0x8A 0x00 0x05 0xFA 0xE4 0x00 0x08 0x0E 0x90 0x0D 0x50 0x0E 0x00

0x0F 0xD0 0xC2 0x98 0x00 0x00 0x41 0x48 0x00 0x00 0x42 0x9A 0x00 0x00 0xC2 0xCF 0x00

0x00 0xC3 0x8D 0xC0 0x00 0x42 0x7C 0x00 0x00 0xC3 0x1B 0x00 0x00 0x41 0xCC 0x00 0x00

0x42 0x95 0x00 0x00 0x41 0x88 0x00 0x00 0x41 0x30 0x00 0x00 0x42 0xF2 0x00 0x00 0xC2

0x0A 0x00 0x00 0xC1 0x12 0x00 0x00 0xC2 0x43 0x80 0x00 0x2A 0xF1

Output format: (4 bytes header+126 bytes payload +2 byes checksum)

1st 4 bytes:0xAA 0x04 0xF6 0x7E: Output header-0xAA; 0x04 0xF6- Data packet number, 0x7E-

Data size. Refer Appendix IV(3) to understand the output header in details.



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Next 4 bytes: 0xB6 0x77 0x68 0x0D: Time stamp in unsigned integer format

Next 4 bytes: 0x00 0x3F 0x28 0xE7: Pressure data in integer format.

Next 2 bytes: 0xE7 0x43: Pressure sensor temperature data in 2 bytes integer format.

Next 48 bytes: 2 bytes each for ax1, ay1, az1, gx1, gy1, gz1, ax2, ay2, az2, gx2, gy2 and gz2 so on

(in 2 bytes integer format)

Next 8 bytes: 2bytes each for temp1, temp2, temp3 and temp4 (in 2 bytes integer format)

Next 48 bytes: 4 bytes float (IEEE 754 floating point representation) each for mx1, my1, mz1,

mx2, my2, mz2, mx3, my3 and so on.

Next 12 bytes: 4 bytes float (IEEE 754 floating point representation) each for fused

magnetometer data of mx, my and mz.

Last 2 bytes: 0x2A 0xF1- Check sum.

How to obtain output of sensor in decimal: To get the actual value of acceleration (from

accelerometer), angular rotation speed (from gyroscope) and magnetic field strength (from

magnetometer), use the scale (multiplication factor) as given in the following table:


(Multiplication

factor)



(1/2048.0)*gvalue

[gvalue is 9.79 m/s^2]

X meter per second square (m/s^2)


2 bytes integer 1/16.4 X degree per second

Magnetic field strength

4 bytes float (IEEE 754 floating point representation)

0.3 X micro Tesla

Temperature 2 bytes integer 1/340 35 Celsius

Pressure Data 4 byte integer 1/4096 X mBar

Temperature Pressure sensor

2 bytes integer 1/480 42.5 Celsius

Some values are picked from the referred data packet and converted to their actual values as

following, for illustration:



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Timestamp (5th to 8th bytes) - 0xB6 0x77 0x68 0x0D (4bytes unsigned

integer)=>30612787733*(1/16e6) => 1913 second

Pressure (9th

to 12th

bytes) - 0x00 0x3F 0x28 0xE7 (4bytes integer) => 4139239, multiply by

scale factor => 4139239*(1/4096) = 1010.556 mBar

Pressure sensor temperature Pressure (13th

to 14th

bytes) - 0xE7 0x43 (2bytes integer) =>-

6333, multiply by scale factor => -6333*(1/480) + 42.5 => 23.8735 ℃

ax1(15th

to 16th

bytes) - 0xFF 0xFE (2 byte integer) => -2, multiply by scale factor => -2*

(1/2048.0)*9.79 => -0.0095 m/s^2

gx1(21th

to 22th

bytes) - 0xFF 0xED (2byte integer) => -19, multiply by scale factor =>-19*

(1/16.4) => -1.1585 degree per second

temp1 (63th

to 64th

bytes) - 0x0E 0x90 (2byte integer) => 3728, multiply by scale factor =>

3728*(1/340)+35 => 45.9647 ℃

mx1 (71th

to 74th

bytes) - 0x98 0x00 0x00 0x41 (4 bytes float) (IEEE 754 floating point

representation) => -76*0.3 => -22.8 mTesla

mx(119th

to 122th

bytes)-0xC2 0x0A 0x00 0x00(4 bytes float) (IEEE 754 floating point

representation) => -34.5*0.3 => -10.5 mTesla

12. State: Read IMUs’ temperature

Command: [53 0 53]

This command is used to initiate reading of internal temperature of onboard inertial sensors by

the internal controller. This command should be run before (13) i.e. Output IMU Temperature

Data.

13. State: Output IMU Temperature Data

Command: [40 pl1 pl2 pl3 pl4 pl5 cs]

MIMU22BL outputs temperature of the selected IMUs in response to this command. The output

consisted of 2 bytes containing the value of temperature, for every selected IMU.

pl1, pl2, pl3 and pl4 are same as in the command for state Output Inertial Data command. pl5 is

128 + the actual output rate divider (1, 2, 3…etc).



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Note: (12) i.e. command Read IMU’s Temperature must be run before this command.

Example:

[53 0 53] (Enables reading IMUs’ internal temperature)

[40 0 0 0 15 129 0 184] (o/p data rate:1 = 250 Hz)

Here are the example data packets containing temperature information data of all the 4 IMUs,

obtained as a result of above set of commands (USB):

0xAA 0xD0 0x28 0x0C 0x00 0x57 0x00 0x19 0x0F 0x16 0x00 0x1B 0x0F 0x2E 0x3F 0x9A 0x04

0x24

Total packet size: 18 bytes(4 bytes Header + 12 bytes Payload + 2 bytes Checksum)

First 4 bytes (Header):0xAA 0xD0 0x28 0x0C (0xAA - command; 0xD0 0x28 - Data packet

number; 0x0C - data packet size). Refer Appendix IV(3) to understand the output header in

details.


integer each for temperatures from imu1, imu2, imu3 and imu4.

Last 2 bytes (Checksum): 0x04 0x24


Data Data Type Scale Factor Addition

Factor Unit

Temperature 2 byte integer 1/340 35 Celsius

Timestamp (5th to 8th bytes) - 0x000x57 0x00 0x19 (4bytes unsigned

integer)=>5701657*(1/16e6) =>0.36 second

Temperature from IMU1 (9th

and 10th

bytes) - 0x0F 0x16 (2byte integer) =>3862, multiply by

scale factor => 3862*(1/340) +35 => 46.3588℃

14. State: High precision IMU (Normal IMU)


pl1 = output rate divider

cs1, cs2: checksum



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With this command, MIMU22BL can be used as a single high precision IMU. The modules are

capable of giving calibration compensated and fused data from the IMU array. This means the

module can be used as a single precision IMU which outputs 3-axis acceleration and 3-axis

gyroscope data. The device outputs g’x, g’y, g’z, a’x, a’y, a’z (ref Fig 2 and Fig 3) – 4 bytes each,

IEEE 754 float type.

Below is the sample data from MIMU22BL lying tilted on a table. The data was collected at data

rate 250Hz.

0xAA 0x17 0x6C 0x1C 0xC3 0xE6 0x7A 0x98 0x40 0x74 0x22 0x11 0x40 0x7B 0x3D 0x0F

0x41 0x03 0x7D 0x75 0x3A 0x16 0xA9 0x04 0xBC 0x38 0xC7 0x5C 0x3B 0x44 0x67 0x1A

0x0B 0x3C ……….FirstPacket

0xAA 0x17 0x6D 0x1C 0xC3 0xEA 0x1A 0x5A 0x40 0x72 0x2A 0x66 0x40 0x74 0x6B 0x15

0x41 0x02 0x00 0x56 0xBB 0x81 0x90 0xAE 0xBB 0xC4 0x02 0x4C 0x3C 0x15 0x68 0x7D

0x0B 0xF7 ……....Second Packet

Total packet size:34 bytes(4 bytes Header + 28 bytes Payload + 2 bytes Checksum)

First 4 bytes (Header):0xAA 0x17 0x6C 0x1C (0xAA - command; 0x17 0x6C - Data packet

number; 0x1C - data packet size). Refer Appendix IV (3) to understand the output header in

details.

Next 28 bytes (Payload): First 4 bytes (unsigned integer) of payload are time stamp; 4 bytes float

each for ax, ay, az, gx, gy, gz.

Last 2 bytes (Checksum): 0x0B 0x3C

How to obtain output of sensor in decimal:To get the actual value of acceleration (from

accelerometer) and angular rotation speed (from gyroscope), use the scale (multiplication factor) as

given in the following table:


(Multiplication

factor)

Unit

Acceleration 4 byte float (IEEE 754 floating point representation)

1 meter per second square (m/s^2)


4 byte float (IEEE 754 floating point representation)

1 radian per second



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Timestamp (5th to 8th bytes) - 0xC3 0xE6 0x7A 0x98 (4bytes unsigned

integer)=>3286661784*(1/16e6) =>205.42 second

ax (9th

to 12th

bytes) - 0x40 0x74 0x22 0x11 (4 byte float) =>3.81457925, multiply by scale

factor =>3.81457925*1 =>3.81 m/s^2

gx (21th

to 24th

bytes) - 0x3A 0x16 0xA9 0x04 ( 4 byte float) =>0.0005747231, multiply by scale

factor =>0.0005747231*1 => 0.0005 degree per second

15. State: High precision IMU with gyro bias estimation


pl1 = output rate divider

cs1, cs2: checksum

This command gives the combined fused precision IMU data after calibration compensation and

adding the estimated gyro bias. The output format will be same as the precision IMU data except

the estimated gyro bias is added with each data set.

16. State: High precision IMU withMagnetometer #3 data

Command:57 pl1 cs1 cs2

Refer the Output mask mode table for how to use pl1.

With this command, MIMU22BL can be used as a single high precision IMU along with fused

and calibrated magnetometer data. The modules are capable of giving calibration compensated

and fused data from the IMU array. This means the module can be used as a single precision IMU

which outputs 3-axis acceleration and 3-axis gyroscope data. The device outputs a’x, a’y, a’z, g’x,

g’y, g’z,m’x, m’y, m’z(ref Fig 2 and Fig 3) – 4 bytes each, float type respectively. Total 46 data

bytes will be there in each packet.

Below is the data packet received through USB with the device placed firmly on the table.

0xAA 0x17 0x6F 0x28 0xC3 0xF1 0xEA 0x29 0x40 0x71 0x61 0x98 0x40 0x79 0x05 0x2B 0x41

0x02 0x66 0x13 0x39 0xDB 0xE9 0x56 0x3C 0xDD 0x6F 0x45 0xBB 0x88 0xB3 0xAC 0xC2 0x0A

0x00 0x00 0x00 0x0C 0xFF 0xFF0x00 0x08 0xFF 0xE4 0x13 0x9C



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Total packet size:46bytes (4 bytes Header + 40 bytes Payload + 2 bytes Checksum)

First 4 bytes (Header):0xAA 0x17 0x6F 0x28 (0xAA - command; 0x17 0x6F - Data packet


details.


float each for ax, ay, az, gx, gy, gz, mx, my, mz.

Last 2 bytes (Checksum): 0x13 0x9C


Data type and units for acceleration (from accelerometers), angular rotation speed (from gyroscope)

and magnetic strength (from magnetometer) are given as in below


(Multiplication

factor)


Acceleration


1




1

X

radian per second

Magnetic strength 4 byte float (IEEE 754 floating point representation)

0.3

X

micro Tesla

Timestamp (5th to 8th bytes) - 0xC3 0xF1 0xEA 0x29 (4bytes unsigned

integer)=>3287411241*(1/16e6) =>205.46 second

ax (9th

to 12th

bytes) - 0x40 0x71 0x61 0x98 (4 byte float) =>3.77158165, multiply by scale

factor =>3.77158165*1 =>3.77m/s^2

gx (21th

to 24th

bytes) - 0x39 0xDB 0xE9 0x56 ( 4 byte float) =>0.0004194478, multiply by scale

factor =>0.0004194478*1 =>0.0004 degree per second

mx(33th

to 36th

bytes) -0xC2 0x0A 0x00 0x00(4 bytes float) => -34.5*0.3 => -10.5 mTesla

17. State: High precision IMU with pressure data

Command: 57 pl1 cs1 cs2

Refer the Output mask mode table for how to use pl1.



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With this command, MIMU22BL can be used as a single high precision IMU along with pressure

sensor data. The modules are capable of giving calibration compensated and fused data from the

IMU array. This means the module can be used as a single precision IMU which outputs 3-axis

acceleration and 3-axis gyroscope data. The device outputs g’x, g’y, g’z, a’x, a’y, a’z,pressure data

respectively. Total 38 data bytes will be there in each packet.

Below is the data packet received through USB with the device placed firmly on the table.

0xAA 0x17 0x6E 0x1C 0xC3 0xEE 0x02 0x2C 0x40 0x6E 0x2F 0xAD 0x40 0x72 0xCF 0x04 0x41

0x00 0xD0 0x13 0x3B 0xCE 0xD8 0x92 0x3C 0x7B 0x8D 0x07 0xBB 0x6F 0xB7 0x7A 0x00 0x3F

0x28 0xE7 0x0D 0x76


First 4 bytes (Header):0xAA 0x17 0x6E 0x1C (0xAA - command; 0x17 0x6E - Data packet


details.


each for ax, ay, az, gx, gy, gz, and next 4 byte integer for pressure data.

Last 2 bytes (Checksum): 0x0D 0x76





(Multiplication

factor)


Acceleration

4 byte float

(IEEE 754

floating point

representation)

1 X

meter per second

square (m/s^2)

Angular rotation

speed

4 byte float

(IEEE 754

floating point

representation)

1 X

radian per second

Pressure Data 4 byte integer 1/4096 X mBar



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Timestamp (5th to 8th bytes) - 0xC3 0xEE 0x02 0x2C (4bytes unsigned

integer)=>3287155244*(1/16e6) =>205.45second

ax (9th

to 12th

bytes) - 0x40 0x6E 0x2F 0xAD (4 byte float) =>3.72166, multiply by scale factor

=>3.72166*1 =>3.72m/s^2

gx (21th

to 24th

bytes) - 0x3B 0xCE 0xD8 0x92 ( 4 byte float) =>0.00631243829, multiply by scale

factor =>0.00631243829*1 =>0.0063 degree per second

Pressure Data (33th

to 36th

bytes) - 0x00 0x3F 0x28 0xE7(4bytes integer) =>4139239, multiply

by scale factor =>4139239*(1/4096) =>1010.56mBar

18. State: High precision IMU with pressure andMagnetometer #3 data

Command:

[49 22 1600 00 00 00 00 00 00 87]

[33 08 13 52 187 00 00 00 00 pl2 cs1 cs2]

With this command, MIMU22BL can be used as a single high precision IMU along with fused

and calibrated magnetometer data plus pressure sensor data will be outputted. A total of 50 data

bytes will be there in each packet each data points are 4 bytes float format.

Example:

[49 22 1600 00 00 00 00 00 00 87]

[33 08 13 52 187 00 00 00 00 1 cs1 cs2]( at 250Hz)

[33 08 13 52 187 00 00 00 00 4 cs1 cs2]( at 25Hz)

Example Output: Below is the data packet received through USB with the device placed firmly

on the table.

0xAA 0x17 0x06 0x2C 0xC3 0xEE 0x02 0x2C 0x40 0x6E 0x2F 0xAD 0x40 0x72 0xCF 0x04 0x41

0x00 0xD0 0x13 0x3B 0xCE 0xD8 0x92 0x3C 0x7B 0x8D 0x07 0xBB 0x6F 0xB7 0x7A 0xC2 0x0A

0x00 0x00 0xFF 0x60 0x08 0x10 0x00 0x0C 0xFF 0xFF 0x00 0x08 0xFF 0xE4 0x13 0xD8


First 4 bytes (Header):0xAA 0x17 0x06 0x2C (0xAA - command; 0x17 0x06 - Data packet


details.


each for ax, ay, az, gx, gy, gz, mz, my, mz and next 4 byte integer for pressure data.

Last 2 bytes (Checksum): 0x13 0xD8



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Data type and units for acceleration (from accelerometers), angular rotation speed (from gyroscope),

magnetic strength (from magnetometer) and Pressure (from Barometer) are given as in below

Data Data Type Scale

(Multiplication

factor)

Addition

Factor Unit

Acceleration

4 byte float (IEEE

754 floating point

representation)

1 X meter per second

square (m/s^2)

Angular rotation

speed

4 byte float (IEEE

754 floating point

representation)

1 X

radian per second

Magnetic strength

4 byte float (IEEE

754 floating point

representation)

0.3 X

micro Tesla

Pressure 4 byte integer 1/4096 X mBar

Timestamp (5th to 8th bytes) - 0xC3 0xEE 0x02 0x2C (4bytes unsigned

integer)=>3287155244*(1/16e6) =>205.45 second

ax (9th

to 12th

bytes) - 0x40 0x6E 0x2F 0xAD (4 byte float) =>3.72166, multiply by scale factor

=>3.72166*1 =>3.72 m/s^2

gx (21th

to 24th

bytes) - 0x3B 0xCE 0xD8 0x92 ( 4 byte float) =>0.00631243829, multiply by scale


mx(33th

to 36th

bytes) -0xC2 0x0A 0x00 0x00(4 bytes float) => -34.5*0.3 => -10.5 mTesla

Pressure (45th

to 48th

bytes) - 0x00 0x08 0xFF 0xE4 (4bytes integer) =>589796, multiply by

scale factor =>589796*(1/4096) =>143.99 mBar

19. State: Request output of state

Command: [32 pl1 pl2 cs1 cs2]

pl1 = state ID

pl2 = output mode

cs1, cs2: checksum

Requests the state connected to the state ID to be output. The output modebyte controls how the

state is output. The states are ordered according totheir IDs in the response.



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Example command

[32 01 32 00 65]

Here is the output for the state ID (0X01) as a result of above set of commands (USB):

0xAA 0x06 0x76 0x04 0x1C 0xFB 0x65 0xD9 0x03 0x7F

20. State: Request output of multiple states

Command:[33 pl1 pl2 pl3 pl4 pl5 pl6 pl7 pl8 pl9 cs1 cs2]

pl1-pl8 = state ID

pl9 = output mode

cs1, cs2: checksum

Requests the states connected to the state IDs to be output. The outputmode byte controls how the

state is output. The states are ordered accordingto their IDs in the response. This command is the

same as justas above withmore IDs. If zeros are given instead of the IDs, no output will be

given.Consequently, the command may be used to request output of up to 8 states.

Example command

[33 16 17 21 22 00 00 00 00 04 00 113]

Here is the output for the state ID (0X10, 0X11, 0X15, 0X16) as a result of above set of

commands (USB):

0xAA 0x05 0xAF 0x38 0x00 0x18 0xC4 0x00 0x00 0x0D 0x30 0x00 0xFC 0x2F 0x88 0x00 0xFE

0x88 0x00 0xFC 0xB8 0x00 0xFD 0x94 0x00 0x00 1A0x68 0x00 0x00 0x0B 0x80 0x00 0xFC

0x2E 0x38 0x00 0x80 0x00 0xFA 0xB8 0x00 0xFD 0x40 0x00 0x00 0x02 0x66 0xA4 0x00 0x00

0x01 0x73 0x17 84

21. State: Set the gravity value

Command:[6 g0 g1 g2 g3 g4 g5 g6 cs1 cs2]

g0 to g6 = g value

cs1, cs2: checksum

With this command the value of g can be input without programming the device. For e.g.to input

value of acc. due gravity as 9.81 m/s2, then input command would be [6 9 8 1 0 0 0 0 0 24].



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22. State: Calibration data value set.

Command: [36 pl1 pl2 pl3 pl4 pl5 pl6 pl7 pl8 pl9 pl10 pl11 pl12 pl13 pl14 pl15 pl16 pl17 pl18

pl19 cs1 cs2]

pl1 = select IMU position

pl2 – pl19 = 4 byte calibration data

cs1, cs2: checksum

With this command the calibration file can be input to MIMU22BL without need to reprogram

the device. pl1 is the IMU# and pl2 to pl19 are the calibration data. pl2 –pl4 are the x-axis

accelerometer calibration components, pl5-pl7 and pl8 – pl10 are y axis and z axis accelerometer

calibration components respectively. Similarly pl11-pl13, pl14-pl16 and pl17-pl19 are the x-axis,

y axis and z axis gyroscope calibration components respectively.

23. State: Input fused Accelerometer Bias

Command:[8 pl1 pl2 pl3 cs1 cs2]

pl1 – pl3 = 4 byte each input data

cs1, cs2: checksum

With this command the fused bias estimation value of the accelerometer can be input without

reprogramming the device. pl1,pl2 and pl3 are the bias estimation of the accelerometer along x, y

and z axis respectively.

24. State: Input Fused Gyroscope Bias

Command:[9 pl1 pl2 pl3 cs1 cs2]

pl1 – pl3 = 4 byte each input data

cs1, cs2: checksum

With this command the fused bias estimation value of the gyroscope can be input without

reprogram. pl1,pl2 and pl3 are the bias estimation of the gyroscope along x, y and z axis

respectively.

25. State: Calibration F & G bias Command: [37 pl1 pl2 pl3 pl4 pl5 pl6 pl7 cs1 cs2] pl1 = select IMU position pl2 – pl7 = 4 byte each data cs1, cs2: checksum;

With this command we can give the individual Bias for each IMU. Pl1 is the IMU selected and

pl2 to pl7 is the bias along x, y and z axis of accelerometer and gyroscope respectively

26. State: Set FG scale



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Command: [68 pl1 pl2 cs1 cs2]

pl1= fs_scale

pl2 = afs_scale

cs1, cs2: checksum;

With this command the range of the accelerometer and gyroscope can be selected. The values of

pl1 can be 0, 8, 16, 24 and pl2 can be 0, 8, 16, and 24 respectively. Refer to Table 3 for details.

Table 6: Accelerometer and Gyroscope scale

Accelero scale

Range

0 ±2g 1 ±4g 16 ±8g 17 ±16g Gyro scale Range

0 500o/s

1

1000o/s

16

1500o/s

17 2000o/s

27. State: Set IMUs Command: [7 pl1 cs1 cs2] pl1= select IMUs position cs1, cs2: checksum; With this command selection of IMUs is possible.Only different combinations of 1, 2 and 4 IMUs

are recommended for correct precision IMU and stepwise data.

To select IMU #3 the command should be [7 8 0 15].

28. State: Software Version

Command: [41 cs1 cs2] cs1, cs2: checksum; MIMU22BL output the version of the programmed firmware. The example output data transmitted via USB 0xAA 0x00 0x01 0x08 0x00 0x000x000x00 0x01 0x00 0x000x00 0x01 0x00 0xB5

Header: 0xAA 0x00 0x010x 08

Version:0x00 0x000x000x00 0x01 0x00 0x000x00 0x01 (1.1) (This is in 8 byte unsigned integer

format)

Check sum: 0x00 0xB5



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29. State: Get Device Id Command: [25 cs1 cs2] cs1, cs2: checksum; MIMU22BL gives the device ID with this command. The example output of the command is given below 0xAA 0x00 0x02 0x08 0x00 0x00 0x16 0x08 0x03 0x00 0x00 0x06 0x00 0xDB

Header:0xAA 0x00 0x02 0x08

ID:0x00 0x00 0x16 0x08 0x03 0x00 0x00 0x06 (This is in 8 byte unsigned integer format)

Check Sum:0x00 0xDB

Note: For all the commands from Sl No. 21 to 27 resetting MIMU22BL will set all the values to

the default programmed values.

30. State: Stepwise Dead Reckoning with true compass heading Command: [67 64 01 31]

MIMU22BL sends out data packet for stepwise dead reckoning along with true compass heading

in response to this command. Use this command only through Bluetooth. It will not work through

USB.Refer Application Note for details.

31. State: Raw IMU and Magnetometer from 4 IMUs

Command1: [48 24 00 72]

Command2: [33 57 58 59 60 185 186 187 188 rd cs1 cs2] MIMU22BL transmitting the inertial sensors’ raw data axi, ayi, azi, gxi, gyi, gzi, magnetometer

raw data mxi, myi, mzi to the application platform.


cs1 cs2- Check Sum.

Example:

Set of commands to obtain data packets containing 4 accelerometers' and 4 gyroscopes' data, 4

magnetometers,.

Example for USB

[48 24 0 0 72]

[33 57 58 59 60 185 186 187 188 rd cs1 cs2]



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Data packets received:

[0xAA 0x1A 0xCB 0x60 0xFF 0x98 0xF7 0xB1 0xFF 0x03 0xFF 0xEE 0x00 0x000x000x00 0xFF

0xC2 0xF7 0xE3 0xFF 0x3B 0x00 0x0E 0x00 0x08 0xFF 0xFF0xFF 0xBB 0xF7 0xB4 0xFF 0x2C

0x00 0x08 0xFF 0xDF 0x00 0x09 0xFF 0xBD 0xF7 0xB4 0xFE 0xB7 0x00 0x0A 0xFF 0xF6 0x00

0x00 0xC2 0x4A 0x00 0x00 0xC3 0x6E 0x00 0x00 0x43 0x24 0x80 0x00 0xC2 0x6C 0x00 0x00

0xC3 0xFA 0x80 0x00 0x43 0x0A 0x00 0x00 0xC2 0x1E 0x00 0x00 0xC3 0x6C 0x00 0x00 0x43

0x10 0x80 0x00 0x42 0x5C 0x00 0x00 0xC3 0x7D 0x00 0x00 0x43 0x15 0x80 0x00 0x29 0x14]

Total packet size: 102 bytes(4 bytes Header + 96 bytes Payload + 2 bytes Checksum)

First 4 bytes (Header):0xAA 0x1A 0xCB 0x60(0xAA - command; 0x1A 0xCB - Data packet


details.

Next 44 bytes (Payload): 2 bytes integer each for ax1, ay1, az1, gx1, gy1, gz1,ax2, ay2, az2, gx2,

gy2, gz2,ax3, ay3, az3, gx3, gy3, gz3, ax4, ay4, az4, gx4, gy4, gz4, and 4 bytes float each for

mz1, my1, mz1, mz2, my2, mz2, mz3, my3, mz3, mz4, my4, mz4.

Last 2 bytes (Checksum): 0x29 0x14





(Multiplication factor)



(1/2048.0)*gvalue

[gvalue is 9.79 m/s^2]



2 bytes integer 1/16.4 X

degree per second

Magnetic field strength

4 bytes float (IEEE 754 floating point representation)

0.3 X

micro Tesla

ax1 (5th

to 6th

bytes)- 0xFF 0x98 (2 byte integer) =>-104, multiply by scale factor =>

-104*(1/2048.0)*9.79 =>-0.4971m/s^2

gx1 (11th

to 12th

bytes) - 0xFF 0xEE (2 byte integer) =>-18, multiply by scale factor =>

-18*(1/16.4) =>-1.0976 degree per second

mx1 (53th

to 56th

bytes) -0xC2 0x4A 0x00 0x00 (4 bytes float) =>-50.5*0.3 => -15.15 mTesla



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32. State: Calibrated IMU and Magnetometer data from all the 4 IMUs

Command1: [49 24 26 00 00 00 00 00 00 00 99]

Command2: [33 37 38 39 40 185 186 187 188 rd cs1 cs2] MIMU22BL transmitting the inertial sensors’ calibrated data axi, ayi, azi, gxi, gyi, gzi,

magnetometer calibrated data mxi, myi, mzi to the application platform.


cs1 cs2- Check Sum.

Example:

Set of commands to obtain data packets containing 4 accelerometers' and 4 gyroscopes'

calibrated data, and 4 magnetometers calibrated data.

Example for USB

[49 24 26 00 00 00 00 00 00 00 99]

[33 37 38 39 40 185 186 187 188 rd cs1 cs2]

Data packets received from USB:

[0xAA 0x69 0x1E 0x90 0x3E 0x66 0x26 0xBF 0xBE 0x82 0x63 0x06 0x41 0x17 0x06 0xD2 0x3C

0x72 0x54 0x98 0xBC 0xC5 0x3A 0x50 0xBC 0x0A 0xEC 0x42 0x3F 0x26 0xF2 0x12 0xBE 0xE3

0xE0 0xFD 0x41 0x1A 0x44 0x99 0xBC 0x0D 0x3A 0xE9 0xBC 0x56 0xDE 0x1A 0xBC 0x19

0xCC 0xDB 0x3C 0x04 0xD5 0xC1 0xBE 0x84 0x25 0xF1 0x41 0x1D 0xF7 0x52 0x3B 0xAB

0xE7 0x39 0x3B 0x49 0xB4 0x68 0xBC 0x23 0xE8 0x19 0x3E 0x5F 0xE3 0x46 0xBE 0xE3 0x2E

0x2A 0x41 0x15 0x40 0x30 0x3C 0x98 0xFB 0x48 0x3B 0xEB 0xCF 0x12 0xBB 0x18 0x51 0x7B

0xC0 0x40 0x00 0x00 0xC0 0x00 0x000x00 0x42 0xA8 0x00 0x00 0xC0 0x40 0x00 0x00 0xC3

0xAC 0x00 0x00 0x42 0x0E 0x00 0x00 0xC1 0xFC 0x00 0x00 0xBF 0xC0 0x00 0x00 0x42 0x2E

0x00 0x00 0x43 0x69 0x80 0x00 0xC0 0x80 0x00 0x00 0x43 0x16 0x80 0x00 0x3A 0x44]

Total packet size: 150bytes (4 bytes Header + 144 bytes Payload + 2 bytes Checksum)

First 4 bytes (Header):0xAA 0x1A 0xCB 0x60(0xAA - command; 0x1A 0xCB - Data packet


details.



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Next 144 bytes (Payload): 4 bytesfloat each for ax1, ay1, az1, gx1, gy1, gz1,ax2, ay2, az2, gx2,

gy2, gz2,ax3, ay3, az3, gx3, gy3, gz3, ax4, ay4, az4, gx4, gy4, gz4, and 4 bytes float each for mx1,

my1, mz1, mx2, my2, mz2, mx3, my3, mz3, mx4, my4, mz4.

Last 2 bytes (Checksum): 0x3A 0x44




Data Data Type Scale Addition

Factor Unit

Acceleration

4 byte float (IEEE

754 floating point

representation)

1 X meter per second

square (m/s^2)

Angular rotation

speed

4 byte float (IEEE

754 floating point

representation)

1 X radian per second

Magnetic strength

4 byte float (IEEE

754 floating point

representation)

0.3 X micro Tesla

ax1 (5th

to 8th

bytes)- 0x3E 0x66 0x26 0xBF (4 byte float) =>0.22475718, multiply by scale factor

=>0.22475718*1=>0.2248 m/s^2

gx1 (17th

to 20th

bytes) - 0x3C 0x72 0x54 0x98 (4 byte float) =>0.0147906765, multiply by scale


mx1 (101th

to 104th

bytes)- 0xC0 0x40 0x00 0x00(4 bytes float) =>-3*0.3 => -0.9 mTesla



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Appendix II

Sample code (Matlab) for Stepwise Dead Reckoning

% Reset stepwise deadreckoning INS

fwrite(com, [52 0 52],'uint8');

fread(com,4,'uint8')

package_number_old = nan;

whileabort_flag==0

if(com.BytesAvailable>=64)

header = fread(com,2,'uint8'); % Header + number + Payload size (-) 4, (+)2

payload = fread(com,14,'float');

step_counter = fread(com,1,'uint16'); % Step counter

fread(com,1,'uint16'); % Checksum

fprintf(file,'%i %i %12.9f %12.9f %12.9f %12.9f %12.9f %12.9f %12.9f %12.9f %12.9f %12.9f %12.9f %12.9f

%12.9f %12.9f\n',step_counter,payload);% for USB

dx = payload(1:4);

dP = Pvec2Pmat(payload(5:14));

pdef=find(eig(dP)<=0);

ifisempty(pdef)

chol(dP,'lower');

end

[x_swP_sw] = stepwise_dr_tu(x_sw,P_sw,dx,dP);

figure(1)

plot([x_sw(1) x_sw_old(1)],[x_sw(2) x_sw_old(2)],'b');

axis equal;

drawnow;

x_sw_old = x_sw;

P_sw_old = P_sw;

end

end

% Stop output

fwrite(com, [50 0 50],'uint8'); % Processing off

fwrite(com, [34 0 34],'uint8'); % all output off

----------------------------------------



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% stepwise_dr_tu

function [x2_out P2_out] = stepwise_dr_tu(x2_in,P2_in,dx2,dP)

% Input matrix

sin_phi = sin(x2_in(4));

cos_phi = cos(x2_in(4));

dR = [cos_phi -sin_phi 0 0;

sin_phicos_phi 0 0;

0 0 1 0;

0 0 0 1];

F = [1 0 0 -sin_phi*dx2(1)-cos_phi*dx2(2);

0 1 0 cos_phi*dx2(1)-sin_phi*dx2(2);

0 0 1 0;

0 0 0 1];

% Update upper layer system

x2_out = x2_in+dR*dx2;

P2_out = F*P2_in*F' + dR*dP*dR';

end



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Appendix III:

How to set calibration parameters using Matlab without compiling MIMU22BL’s firmware

Calibration file consists of fused accelerometer bias (ACC_BIAS) and fused gyroscope bias

(GYRO_BIAS). It also consists of calibration matrix. The first 18 elements of each row is the calibration

gain and the next 6 element is the individual bias of each IMUs. MIMU22BL consists of 4 IMUs so rest

of the elements 28 calibration rows is 0. An example of the calibration file is given below.

#define FLOG2_NR_IMU 2

#define ACC_BIAS { 321455, -381480, -1784994 }

#define GYRO_BIAS { -109378, 807557, -314605 }

#define CALIBRATION_MATRIX \

{ \

{ 32737, 0, 0, -21, 32889, 0, 113, -76, 32779, 32768, 0, 0, 0, 32768, 0, 0,

0, 32768, -189318, -1285370, -10636239, 217070, 771033, 89464 },\

{ -258, -32733, 112, -32949, 259, -115, 127, -270, -32657, -258, -32766, 112, -32766, 257,

-115, 113, -113, -32767, 1031829, 231703, 2583073, -332858, 132476, -843920 },\

{ 32582, -44, 181, 43, 32848, -47, -408, 4, 32552, 32767, -44, 182, 44, 32768, -

47, -182, 48, 32767, -233539, -870378, -4025710, -585304, -602875, 44841 },\

{ 56, -32663, 128, -32840, -62, -281, 420, 96, -32611, 60, -32767, 129, -32765, -62, -

280, 281, -128, -32765, 727064, 381943, 4940699, 261427, 2930711, -535587 },\

{0, 0, 0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},\

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \



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Page 49

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, \

Each of the values represented in the above example is in float (4 bytes). The example file is converted to

bytes, so each element of the example calibration file consists of 4 bytes each. So the fused accelerometer

and gyroscope bias consists of (3x4) 12 bytes each. For e.g. the first element of ACC_BIAS is 321455

and that of GYRO BIAS is

Below are the examples

(i) 321455 = 0x4E7AF;

Hexadecimal 0x00 0x04 0xE7 0xAF

Decimal 0 4 231 175

Now 321455 is replaced by 0 4 231 175

(ii) -109378 = 0XFFFE54BE

Hexadecimal 0xFF 0xFE 0x54 0xBE

Decimal 255 254 84 190

Similarly -109378 is replaced by 255 254 84 190

This format is followed for all the elements for calibration output file.



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Page 50

Each row of the calibration matrix consists of (18x4) 72 bytes representing the calibration gain shown

below as imu_mask(i) and the individual IMU bias consists of (6x4) 24 bytes each depicted as

imu_bias(i) .

f_log2 = 4;

f_bias = [0 4 231 175255 250 45 216255 228 195 94];

g_bias = [255 254 84 1900 12 82 133255 251 51 19];

imu_pos0 = 0;

imu_pos1 = 1;

imu_pos2 = 2;

imu_pos3 = 3;

imu_mask0 = [0 0 127 225 0 0 0 0 0 0 0 0 255 255 255 235 0 0 128 121 0 0 0 0 0 0 0 113255 255 255 1800

0 128 11 0 0 128 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 128 0];

imu_mask1 = [255 255 254 254255 255 128 350 0 0 112255 255 127 750 0 1 3255 255 255 1410 0 0 127 255 255

254242255 255 128111255 255 254 254 255 255 128 20 0 0 112255 255 128 20 0 1 1255 255 255 14100 0 113255

255 255 143255 255 128 1 ];

imu_mask2 = [ 0 0 127 70 255 255 255 2120 0 0 1810 0 0 430 0 128 80 255 255 255 209255 255 254 1040 0 0

40 0127 40 0 0 127 255 255 255 255 2120 0 0 1820 0 0 440 0 128 0 255 255 255 209255 255 255 740 0 0 480 0

127 255 ];

imu_mask3 = [0 0 0 56255 255 128 1050 0 0 128 255 255 127184 255 255 255 194 255 255 254231 0 0 1 164

0 0 0 96 255 255 128157 0 0 0 60255 255 128 10 0 0 129 255 255 128 3 255 255 255194 255 255 2542320 0

1 25255 255 255 128255 255 128 3];

imu_bias0 = [255 253 28 122255 236 99 6255 93 180 490 3 79 238 0 11 195 2170 1 93 120];

imu_bias1 = [ 0 15 190 1490 3 137 230 39 106 33255 250 235 1980 2 5 124 255 243 31 112 ];

imu_bias2 = [ 255 252 111 189255 242 184 22255 194 146 146255 247 17 168255 246 205 50 0 175 41];

imu_bias3 = [ 0 11 24 240 5 211 2470 75 99 1550 3 253 510 44 184 23255 247 211 221];

Matlab script for loading above calibration file into MIMU22BL is shown below.

header_f_log = 5;

header_g_bias = 9;

header_f_bias = 8;



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header_c_bias = 37;

command_f_log = [header_f_loglog2(f_log2)];

command_f_log= [command_f_log (sum(command_f_log)-mod(sum(command_f_log),256))/256

mod(sum(command_f_log),256)];

fwrite(com,command_f_log,'uint8');

command_g_bias = [header_g_biasg_bias];

command_g_bias = [command_g_bias (sum(command_g_bias)-mod(sum(command_g_bias),256))/256

mod(sum(command_g_bias),256)];

fwrite(com,command_g_bias,'uint8');

command_f_bias = [header_f_biasf_bias];

command_f_bias = [command_f_bias (sum(command_f_bias)-mod(sum(command_f_bias),256))/256

mod(sum(command_f_bias),256)];

fwrite(com,command_f_bias,'uint8');

command_calib_mat = [header_calib_mat imu_pos0 imu_mask0];

command_calib_mat = [command_calib_mat (sum(command_calib_mat)-

mod(sum(command_calib_mat),256))/256 mod(sum(command_calib_mat),256)];

fwrite(com,command_calib_mat,'uint8');













command_c_bias = [header_c_bias imu_pos0 imu_bias0];

command_c_bias = [command_c_bias (sum(command_c_bias)-mod(sum(command_c_bias),256))/256

mod(sum(command_c_bias),256)];

fwrite(com,command_c_bias,'uint8');






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fwrite(com,[50 0 50],'uint8'); % Stop processing

fwrite(com,[34 0 34],'uint8'); % Stop output (and empty buffers)

whilecom.BytesAvailable

fread(com,com.BytesAvailable,'uint8');

end

fclose(com);

Here header_f_log = Log2(No. of IMUs)



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Appendix IV

1. How to ensure integrity of the output data packet by using Checksum

The last two bytes of the output packets are Checksum, which is 16-bits unsigned integer.

MIMU22BL computes checksum by adding rest of the bytes and putting result in the last two bytes

of the data packed as unsigned integer. When the data packet is received, Checksum is also extracted

from the data packet (except last two bytes), and compared with the last two bytes which are the

Checksum computed by the MIMU22BL. The two Checksums must match.

Steps to extract and compute Checksum from IMUs data packet are described below

(i) Extracting IMU’s Checksum from its output data packet

Below is the method (pseudo code) to obtain last two bytes of the packet and convert to integer:

intgetChecksum(Byte[] data){

int size = data.length; // Output data packet size

intfirstByte = data [size-2] & 0xFF; // Saving first byte of checksum as 4-bytes integer

intsecondByte = data [size-1] & 0xFF; // Saving second byte of checksum as 4-bytes

integer

returnfirstByte*255 + secondByte; // Obtaining 4-bytes integer value of the checksum

}

(ii) Computing Checksum from the received data packet

Below is the method (pseudo code) to compute checksum from received data packet:

intcalculateChecksum(Byte[] data){

int sum = 0; // ‘sum’ is 4-bytes integer

for (inti = 0; i< data.length-2 ; i++) // Add all the bytes of data packet except last two

sum += data [i] & 0xFF; // Add and accumulate

return sum%65536; // This is the final checksum

}



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2. Format of Acknowledgement packet

MIMU22BL transmits 4 bytes Acknowledgement (ACK) packet in response to any command

from the application platform. First byte of the ACK packet is always 0xA0, second byte is the

first byte of the command (also known as command header) and last two bytes are the Checksum.

For example, following is the 4-bytes ACK packet in response to processing off command [50 0

50].

"0xA0 0x50 0x00 0xF0"

0xA0 = Acknowledgement state (Denotes ACK packet)

0x50 = command header (First byte of command packet)

0x00 0xF0 = Checksum

3. Format of the Output Header

Each data packet contains 4 bytes output header, payload and 2 bytes checksum. The 4 bytes

output header contains [0xAA pl1 pl2 pl3]. Explanation of each byte is given below:

0xAA- Packet Header: This marks the beginning of a new data packet.

pl1 and pl2 are 2 bytes packet number in 2 byte unsigned integer format. If the packet

number exceeds 65535 (i.e overflow occurs) then it will show the packet number

modulus 65536 (Packet_number%65536).

pl3 is the payload size in single byte unsigned integer format. . If the payload size

exceeds 255 (i.e overflow occurs) then it will show the payload size modulus 256

(Payload%256).

4. PKG ACK - Send acknowledgement for last data packet received from MIMU22BL

PKG ACK is different from ACK. This PKG ACK is send by the application platform to MIMU22BL on successfully receiving a data packet (only if lossless mode is set).



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PKG ACK consists of 5 bytes:

i. 1st byte: 01

ii. 2nd byte: P1 (First byte of data packet number of last data packet received)

iii. 3rd byte: P2 (Second byte of data packet number of last data packet received)

iv. 4th byte: Quotient of {(1+P1+P2) div 256}

v. 5th byte: Remainder of {(1+P1+P2) div 256}

Pseudo code for ACK generation: i=0;

for(j=0; j<4; j++)

{

header[j]=buffer[i++]& 0xFF; // 4-bytes assigned toHEADER; }

packet_number_1=header[1]; // First byte of data packet number

packet_number_2=header[2]; // Second byte of data packet number

ack = createAck(ack,packet_number_1,packet_number_2); // Acknowledgement created

<code to send acknowledgement> //ACKNOWLEDGEMENT SENT

// HOW TO CREATE ACKNOWLEDGEMENT

// ACK consists of 5 bytes

createAck(byte[] ack, int packet_number_1, int packet_number_2)

{

ack[0]=0x01; // 1st byte

ack[1]= (byte)packet_number_1; // 2nd

byte

ack[2]= (byte)packet_number_2; // 3rd

byte

ack[3]= (byte)((1+packet_number_1+packet_number_2-(1+packet_number_1+packet_number_2) %

256)/256); // 4th

byte – Quotient of {(1+P1+P2) div 256}

ack[4]= (byte)((1+packet_number_1+packet_number_2) % 256); // 5th

byte- Remainder of {(1+P1+P2)

div 256}

returnack;

}

Documents

MIMU22BL Integration Guide Revision 1. 12 ±Integration Guide Doc: MIMU22BL-integration-guide.pdf Revision: 1.12 Release Date: 02 May, 2019 w w w . in e r t ia le le m e n t s . c