DC Motor PID Control

DC Motor Research Documentation

Navigation

• DC Motor Research Documentation : Motor Identification and PID Control
• Build the RP2040 Firmware
• Python Script Installation

DC Motor Speed and Position Control with Raspberry Pi Pico RP2040 and embassy-rs 🦀. This is the framework to write a firmware code with USB communication and flash storage feature. We use Python to communicate with the firmware API via serial communication. It's possible to scale up the project with another applications. Please refer to the DC Motor Research Documentation for detail research on the DC Motor.

Features

The table below shows the firmware features:

Features	Details
PID Motor Control	Speed Control → Step Motion Profile Only Position Control: Step Motion Profile Trapezoid Motion Profile Use Fixed-point Numbers Calculation via fixed
Raw Byte Communication via USB CDC ACM	Get and Set Firmware Config Save Firmaware Config on the Flash Memory Controlling Motor based on PID Control Mode Firmware Logger up to 1kHz sampling frequency
Encoder Reading Method	RP2040 PIO via embassy_rp::pio_programs::rotary_encoder::PioEncoder
Flash Storage	Save firware config on the flash memory to simulate EEPROM via sequential_storage
Multicore	CORE0 → USB Communication + Logger + Flash Storage CORE1 → Motor Control (200 Hz sampling rate)

Hardware

Specification

Components	Specification
Microcontroller	Raspberry Pi Pico RP2040
Motor	Motor DC JGA25-370 12V Gearbox (1200 RPM)
Motor Driver	BTS7960

GPIO Map

We can see the GPIO pin list on the firmware/main/src/resources/gpio_list.rs

Pin Name	Motor_0 Pin	Motor_1 Pin
Motor_PWM_CW_PIN	GP15	GP3
Motor_PWM_CCW_PIN	GP14	GP2
Encoder_PIN_A	GP6	GP4
Encoder_PIN_B	GP7	GP5
PWM Slice	PWM_SLICE7	PWM_SLICE1

Getting Started

We have two main directories: firmware and script as shown on the graph below. To start with this project you can clone this repository and follows the instruction below.

.
├── assets
├── firmware
│   ├── main
│   │   └── src
│   │       ├── control
│   │       ├── resources
│   │       ├── tasks
|   |       └── main.rs # Primary RP2040 PID DC Motor Control
│   └── playground      # Experimental project (USB, Flash Storage)
└── script
	├── BasicFunction
	├── Board
	├── Config
	├── DeviceOpFuncs 	# Device OP file folder to call the firmware API
	├── FWLogger
	├── Tool
	└── run.py      	# Python Script to Communicate with the Firmware

firmware

• Create the RP2040 firmware binary (elf or uf2 ) to be flashed on the RP2040
• The main code of DC motor control is on firmware/main
• You can also try some features on firmware/playground/ before merge them to the main.
• To build the project you can go to this link for build firmware

script

• Firmware API

  • The API to communicate with RP2040 is on script/DeviceOpFuncs/DCMotor.toml
  • The structure of the communication is follows this pattern:

   Command Format:
   	Send Command        --> [COMMAND_HEADER:u8] [OP_CODE:u8] [PARAMETER]
   	Response Command    --> [COMMAND_HEADER:u8] [ERROR_CODE:u8] [OP_CODE:u8] [RESPONSE_MESSAGE]
  
   Event Format:
   	Received Event      --> [EVENT_HEADER:u8] [EVENT_CODE:u8] [MOTOR_ID:u8]
  
   Logger Format:
   	Received Log Data   --> [LOGGER_HEADER:u8] [sequence:u8] [time_stamp:u32] [DATA_LOG:[i32;5]]
   	DATA_LOG:[i32;5] =  [current_pos, current_speed, commanded_pos, commanded_speed, commanded_pwm]
  

  • You can see the TOML file for more detail.

  • ⚠️ Please make sure to match the TOML file with the actual firmware op_code, input, output, and data type.

• Python Script

  • Python script to communicate with the RP2040 including the firmware logger by executing the run.py.
  • To run the python code you can type:

    python -i script/run.py

  • Or you can use uv python package manager for automatically handle the dependencies with this command:

    cd script
    uv run python -i run.py

Project Example

• On script/run.py you can create custom code to command the RP2040. We have created the example such as:

Example	Positive Direction	Negative Direction
Open Loop
Speed Control
Position Control

DC Motor Research Documentation