ROS/Arduino Serial Motor Demo

This is demonstration of a ROS 2 interface to an esp32 running differential-drive motor control code.

The codes are as follows.

• esp32_2_pi_demo - Demonstration for wifi communication from esp32 to pi
• esp32_motor_demo - ros2 code for the motor driver and gui nodes
• esp32_motor_demo_msgs - support variables for the esp32_motor_demo code
• ros_esp32_bridge_wifi - sketch for the esp32, to run the wireless communications. Done in platformio
• ros_esp32_bridge_serial - sketch for the esp32 to run the serial communication with the ros2. Done in arduino IDE. Only works with original serial ros2 demo.

Components

The esp32_motor_demo package consists of two nodes, driver.py and gui.py. The idea is that the driver can be run on an onboard PC inside a robot (e.g. a Raspberry Pi), interfacing with the lower-level hardware. The driver exposes motor control through ROS topics (see below), which are to be published by the user's software.

The GUI provides a simple interface for development and testing of such a system. It publishes and subscribes to the appropriate topics.

Driver configuration & usage

The driver has a few parameters:

• encoder_cpr - Encoder counts per revolution
• loop_rate - Execution rate of the esp32 code (see Arduino side documentation for details)
• esp32_ip - This is the ip of the esp32. I'm using a static ip (default http://192.168.1.211)
• baud_rate - Obsolete since I'm using a wifi connection
• serial_port - Obsolete
• serial_debug - Enables debugging of serial commands (default false)

To run, e.g.

ros2 run esp32_motor_demo driver --ros-args -p encoder_cpr:=3440 -p loop_rate:=30 

It makes use of the following topics

• motor_command - Subscribes a MotorCommand, in rads/sec for each of the two motors
• motor_vels - Publishes a MotorVels, motor velocities in rads/sec
• encoder_vals - Publishes an EncoderVals, raw encoder counts for each motor

GUI Usage

Has two modes, one for raw PWM input (-255 to 255) and one for closed-loop control. In this mode you must first set the limits for the sliders.