4WD rover arduino firmware

Arduino Due firmware for 4WD rover kit with a Python client for integration with Raspberry Pi, ROS, etc.

Current implementation status:

Feature	Status
Telecommand and Telemetry serial interface.	✔️
Basic motor control with L298N.	✔️
Motor control with velocity profiles.
Navigation & State Estimation - AHRS with MPU9250.	✔️
Navigation & State Estimation - GPS.
Navigation & State Estimation - Odometry (wheel encoders).
Navigation & State Estimation - Data fusion.

Dependencies

• arduino-cli
• Bolder Flight Dynamics MPU9250

Rover hardware setup

Part list

Platform:

• 1x Arduino Due.
• 1x L298N.
• 4WD Chassis kit:
  • 4x DC Motors wtih gear reduction + wheels.
• 1x Battery holder x2 18650 (8.4v).
• 2x 18650 batteries.

Payload:

• Raspberry Pi 3B+.
• Webcam C170.

Wiring

Arduino - L298N

L298N Pin	Arduino Due Pin	Wire Color
ENA	2	Black
IN1	3	Yellow
IN2	4	Brown
IN3	5	Red
IN4	6	Black
ENB	7	Green

L298N - Motors

L298N Pin	Motor	Wire Color
OUT1	LF, LB (-)	Black
OUT2	LF, LB (+)	Red
OUT3	RF,RB(+)	Red
OUT4	RF,RB(-)	Black

With Car facing forwards: LF=Left/Front, RB=Right/Back,etc.

Serial Interface with Raspberry Pi 3B+

Arduino Due Pin	Raspberry Pi 3B+ Pin	Wire Color
GND	6 (GND)	GND
19 (RX1)	8 (TXD)	White
18 (TX1)	10 (RXD)	Yellow

Arduino - MPU9250

Arduino Due Pin	MPU9250 Pin	Wire Color
VCC	3.3V	Red
GND	GND	Black
SDA (20)	SDA	Greem
SCL (21)	SCL	Yellow

Arduino - GPS

Arduino Due Pin	GPS Pin	Wire Color
GND
RX2
TX2

SW interface

The SW protocol uses the following packet format:

"PKT!<payload><crc16>\n"

where:

• "PKT!" is the sync word.
• Payload is a sequence consisting of up to 64 bytes.
• crc16 is the crc16 of the payload.
• \n is the packet terminator.

Two types of packets are used:

• Commands: the payload consists of an OPCODE plus command-specific data.
• Reports: the payload consists of a REPORT_ID and report specific data. Two special types of reports are mandatory:
  • Telemetry.
  • Command execution status.

Commands

Opcode	Mnemonic	Description	Parameters
0x00	REQUEST_TMY	Request telemetry. A general telemetry report is generated.	None.
0x01	LED_ON	Turn on test led.	None.
0x02	LED_OFF	Turn off test led.	None.
0x03	UPDATE_MOTOR_SPEEDS	Update motor speeds.	See details below.

0x03 UPDATE_MOTOR_SPEEDS

Update motor speed values. Each motor speed is specified as an int16 from -255 to 255.

Byte Offset	Description
0	Motor A Speed MSB.
1	Motor A Speed LSB.
2	Motor B Speed MSB.
3	Motor B Speed LSB.
4	Flags. b01: Enable Motor A, b10: Enable Motor B.

Reports

0x80 GENERAL_TELEMETRY_REPORT

This report is generated in response to a REQUEST_TMY command.

Offset	Parameter	Description
0	REPORT_TELEMETRY_REQUEST(0x80)	Report Id.
1	TMY_PARAM_ACCEPTED_PACKETS	Accepted packets (telemetry request do not increase this counter).
2	TMY_PARAM_REJECTED_PACKETS	Rejected packets (telemetry request do not increase this counter).
3	TMY_PARAM_LAST_OPCODE	Last opcode received.
4	TMY_PARAM_LAST_ERROR	Error code from last opcode executed.

0x81 REPORT_COMMAND_EXECUTION_STATUS

This report is generated after a command is executed.

Offset	Parameter	Description
0	REPORT_COMMAND_EXECUTION_STATUS(0x81)	Report Id.
1	OPCODE	Executed opcode.
2	STATUS_CODE	Opcode execution status code.

Firmware build instructions

Tested on Arduino Due. List available boards.

arduino-cli board list
Port         Type              Board Name                     FQBN                          Core       
/dev/ttyACM0 Serial Port (USB) Arduino Due (Programming Port) arduino:sam:arduino_due_x_dbg arduino:sam

Build and upload (from one directory upwards):

arduino-cli compile --fqbn arduino:sam:arduino_due_x rover-firmware
arduino-cli upload -p /dev/ttyACM0 --fqbn arduino:sam:arduino_due_x rover-firmware

Firmware tests

Jupyter: see RoverBasicBenchTest.ipynb

cd python
jupyter notebook

or:

cd python
python rover_test.py # or python silent_rover_test.py