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EFM32 Series 0: Low Energy Sensor (LESENSE) Interface
2
LESENSE – Low Energy Sensor Interface
Analog eventsCapacitive, inductive or resistive sensors
3
LESENSE – Low Energy Sensor Interface
Analog eventsCapacitive, inductive or resistive sensors
Generic MCUWake-up periodically to detect the events
4
LESENSE – Low Energy Sensor Interface
Analog eventsCapacitive, inductive or resistive sensors
Generic MCUWake-up periodically to detect the events
EFM32 MCUWake-up only on the events
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LESENSE – Low Energy Sensor Interface
EFM32 MCUConditional wake-up(e.g. on every 2nd event)
Analog eventsCapacitive, inductive or resistive sensors
Generic MCUWake-up periodically to detect the events
EFM32 MCUWake-up only on the events
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LESENSE – Low Energy Sensor Interface
EFM32
ZZ
ZZ Z
• Autonomous sensing in Deep Sleep
• LESENSE with central control logic
• ACMP for sensor input
• DAC for reference generation
• Measure up to 16 sensors
• Inductive (LC)
• Capacitive (eg. capacitive buttons)
• General analog sensors (e.g. resistive)
• Programmable state machine
• 16 states, 4 input channels
• Can do quadrature decoding
•Interrupt/PRS on sensor events
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LESENSE – Requirements & Interactions
CPU and Memory
Peripheral Reflex System
SecuritySerial Interfaces
Clock Management
I/O Ports Timers and Triggers Analog Modules
Energy Management
High Freq
Crystal Osc
High Freq
RC Osc
Low Freq
Crystal Osc
Low Freq
RC Osc
ARM Cortex-M3
processor
Voltage
Regulator
Voltage
Comparator
Power-on
Reset
Brown-out
Detector
USART UART
Low
Energy
UART
I2CGeneral
Purpose
I/O
External
Interrupt
Pin
Reset
ADC
LCD
Controller
Analog
Comparator
AES
Accelerator
Ultra Low Freq
RC Osc
Timer/
Counter
Low Energy
Timer
Backup
RTC
Pulse
Counter
Watchdog
Timer
Low Energy
Sensor IF
Memory
Protection
Unit
Operational
Amplifier
DAC
Auxiliary
RC Osc
External
Bus
Interface
USB
Embedded
Trace
Macrocell
Flash
Program
Memory
RAM
Memory
Debug
InterfaceDMA
ARM Cortex-M3
processor
Memory
Protection
Unit
TFT
Driver
Auxiliary
RC Osc
Back-up
Power
Domain
Real Time
Counter
GPIO
Wake-up
32-bit bus
Available down to: EM1
(Sleep)
EM0
(Run Mode)EM2
(Deep Sleep)
EM3
(Stop Mode)
EM4
(Shutoff Mode)
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Capacitive Measurement
Z z Z
LESENSE300
412
<
Compare
Counter
ACMP
<CPUInterrupt!
240
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Resistive/General Measurement
EFM32
Sensor
Power supply
Output
CPU
Z z Z
LESENSE
Excitation
Input
SampleSampleSample
ACMP
-
+
..101..
PRS
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LESENSE Inductive Measurement
Metal
No metal
EFM32
ACMP0_CH0
DAC0_OUT0
Fixed at Vdd/2
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LESENSE Inductive Measurement – Timing
• LESENSE scans all the
enabled channels at a
configurable frequency.
Analog Comparator and DAC Enabled
Sampling Window
EFM32
ACMP0_CH0
DAC0_OUT0
LESENSE10
<
6
Acmp and DAC on
Excitation (pull CH0 pin low) High-Z inputHi-Z
Acmp gated to counter
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Feel the flow!!
LESENSE
Pulse Counter
011011
Flow
EFM32
000CH1
CH0
001002003004005006007008009010011
CPU
Compare
Count
Interrupt!!Z z
Z
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State Machine - Slide to Wake up!
LESENSE
2 3 4
5
ACMPCPU
Z z Z
EFM32
1
2 3 4
5Decoder
Interrupt!
Count & Compare
CPU
• Autonomous Gesture Detection
• Up to 16 Different States
• Output to PRS or Interrupt
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Slide to Wake up!
LESENSE
2 3 4
5
ACMPCPU
Z z Z
EFM32
1
2 3
Decoder
Count & Compare
• What happens on incomplete
gesture ??
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LESENSE – Statemachine / Decoder
Next State Alternative A
Decision Block
CurrentState
Next State Alternative A
Next State Alternative B
Decision Block
Input
PRS Output Interrupt
Next State Alternative A
Next State Alternative B
Decision Block
Next State Alternative A
Next State Alternative B
Decision Block
Input
• Up to 16 states.
• 4 Inputs from scan-result or PRS.
• 2 configurable next states per transition.
• 3 output action signals on state transition.
• Interrupt on state transition.
• One transition per scan-sequence.
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LESENSE Overview
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Measurement Timing
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www.silabs.com/efm32
