Modbus to DNP3 Protocol Converter

Group 24: Joshua Daly, CpE Daniel Doherty, CpE Mac Lightbourn , EEJoseph Wilkinson, EE

Controllers like this one alternate which pumps in the lift station are active to maintain the desired flow rate and water level.

Other functions include ventilation control and alarms for high water or odor levels.

Many controllers are networked together and there is no industry-standard network protocol.

Modbus vs. DNP3

Project motivation: MPE needs to allow for communication between network nodes that are using these different protocols.

Created Market Difficulty of Implementation

Equipment Costs

Open Standard?

Records time-stamped event

sequences?

Efficiency (bytes transferred for a given

bandwidth)

Modbus 1979 Widely used in all SCADA industries Low $100+ No With Difficulty Average

DNP3 1993

Sometimes used in water/

wastewater applications

High $500-$3000 Yes Yes Very High

Four-Semester Plan

Device BuildUser InterfaceInitialization

Phase IINetwork CommunicationsSecurity

Phase I

Key Specs

Operates between -10 and 80 degrees Celsius Protects against surges of 120 V MCU clock has a backup battery that can power the

MCU for 12 hours if power is lost Sends alarm to master device when power is lost Takes Ethernet input and gives Ethernet output Allows user to view and change networking

parameters Logs 20,000 events, even when power is lost, with

98% fidelity Records date and time of each event to millisecond

accuracy Notifies master device of all events with 95% fidelity

Four-Layer PCB Design

Choosing an MCU

Microchip PIC32TI Stellaris ARM

Cortex M3Freescale

MC9S12NE64Freescale

MC9S12XDP512Price/unit

(bulk purchases) $1.58+ $1.00+ $6.93+ $13.07+

Pins 28, 36, or 44 64, 100, 144, or 156 80 or 112 80, 112, or 144

Processor Speed 80 MHz 80 MHz 16 MHz 80 MHz

Memory 128 KB SRAM256 KB SRAM, 32

KB Flash64 KB Flash, 8 K

RAM512 KB Flash, 64 KB

SRAM

Special Considerations

Cheap/free dev tools; extensive application notes

Ethernet-ready

Ethernet-ready with application notes; already widely used by

the sponsor

XGate coprocessor module; Non-

multiplexed external bus interface; in

same family as MCUs used by our sponsor

Ethernet Integration

Ethernet jacks include integrated magnetic isolation modules

Input and output both feature a dedicated Ethernet controller

Modbus input and DNP3 output interface with the MCU via SPI ports for high speed communications

ENC28J60 J00-0045NL

Noise Due to SPI Lines

MOSI and MISO signals transmit at frequencies of 10-100 MHz

Rapid logic transitions on these signals combined with the effective series inductance of the traces lead to a field effect

The result is noise

Noise Due to SPI Lines

To reduce the noise, we took three measures

1. We placed pull-up resistors close to the microcontroller

2. We used large-value resistors for the pull-ups and large-value bypass capacitors

3. We isolated the MOSI and MISO lines with copper ground

Push Buttons and LEDs

Coding Environments

Visual Studio Used while PCB board was in

development Familiar environment

Code Warrior Freescale MCU Optimization of .s19 file

Firmware Overview

Creation of data Structs to maintain parameters

Menu system Allows user to adjust stored parameters Strict requirements from the sponsor

Initialize all components on the PCB Handle all button functionality

Firmware Challenges

Project requirements changed midway through

Integration of all parts on PCB Delayed action based on buttons Code must be well documented and

easily modified

Data Storage

Stored in contiguous blocks

Storage requirements Factory defined User defined

Buttons

Required Guidelines

Button Functionality

Menu Navigation

Time Delayed press

Screen

Display Screen 3 7-segement displays

Mimic the current display used by MPE

Allows user to visually navigate and set parameters

Power Subsystem

Power Supply Requirements

Takes in 24 V DC This supply is shared with other

components in the lift station control panel

This is a low voltage in comparison to other devices being used in industrial applications

The low voltage bypasses some of the testing requirements for meeting UL standards

Power Supply Requirements

Surge Protection Must handle currents up to 80 A Must correct irregular voltages Multiple devices are connected in

a shunt configuration for combined benefits

Power Supply Requirements

Type of Device Lifetime-number ofsurges

Response Time

Transient Voltage Suppression Diode

- 1 ps

Metal Oxide Varistor 1000 surges 1 ns

Zener Diode infinite 1 us

Gas discharge tube 20 surges 5 us

Input Surge Protection

Power Supply Requirements

Must be fed through a DIN rail mount All devices in the lift station

control panel attach to one rail Mount also serves as chassis

ground for added surge protection

DC/DC Converter

Voltage is stepped down to 3.3 V and then fed to the power plane

To conserve power, a passive switching regulator was chosen

Our configuration is a common circuit with extensive application notes

FinancialsComponent Price Quantity Total

Clock $2.34 4 $9.36Clock-Back Battery $4.28 1 $4.28Microcontroller $22.85 1 $22.85Switching Regulator $3.75 1 $3.75Schottky Diode $0.55 1 $0.55TVS Diode $0.73 1 $0.73Inductor $3.56 1 $3.56LCD Driver $1.75 1 $1.753-Digit 7-Segment Display

$2.91 1 $2.91

Ethernet Controller $5.83 2 $11.66Ethernet Connector $4.73 2 $9.46Super-Red LED $1.08 2 $2.16Cyclone Pro Programmer

$298.80 1 $298.80

Metal Oxide Varistor $0.56 1 $0.56Din Rail Connector $1.54 1 $1.54Case Donated 1 DonatedPCB $80.00 1 $80.00Pin Connector $0.15 3 $0.45Resistor $0.02 17 $0.34Capacitor $0.12 20 $2.40Total     $457.11

Overall

Testing

Firmware

Hardware

Research

0 10 20 30 40 50 60 70 80 90

Completion Timeline