This microcontroller code is designed to run on the STM32G431 family of processors. The initial code was generated by the STMCubeMX application for Microsoft Windows. To compile this project the STMCubeIDE is needed. After downloading, open the project file and click the build button.
This file holds some notes about the test implementation that I am using to show off a final implementation for this section of the project.
The encoder that I am using for testing is a Bourns Audio 3315. This encoder has a counting range from 0-16. An encoder counting range is the number of mechanical ticks that an encoder has. Usually an range of 0-16 is pretty good for user input. For motor applications this number is very low. A low resolution means that the mapping from ticks to degrees is of low resolution. With the current test configuration I was able to get a mapping of around 5 degrees per tick on the encoder. In a production motion control system this would be abysmal. For the testing application it should be good enough to show that something is working.
PWM for an actual motor control situation would be designed more strictly. In this demonstrations example I set the PWM period to a reasonable default that will clearly show the system working. In an actual motor control situation the period and duty cycle would have to match the motor under control. Since I do not have an actual motor for testing I had to make some liberal default value choices. To make the math easy, I chose a PWM period of 1ms with 360 duty cycle deviations. That means that the duty cycle can be set in increments of 360. As an example, a 50% duty cycle would have a value of 180 in the counter compare register. This simplification makes the conversion from encoder ticks to PWM output straightforward. A 1ms period makes visualization on an oscilloscope easy.
When the system is powered on the PWM output is disabled by default. To enable the output send a 55 AA 01 52 message.
Here are a few test message that can be used for demonstration or testing. All numerics are sent and received in big endian.
- 55 AA 05 45 00 01 5F 90 - Set encoder expected value to 90 deg
- 55 AA 05 50 00 00 05 DC - Set new kp value of 1.5
- 55 AA 05 49 00 00 00 7D - Set new ki value of 0.125
- 55 AA 05 44 00 00 00 32 - Set new kd value of 0.05
- 55 AA 01 70 - Request kp value
- 55 AA 05 70 MN OP QR ST - Returned message's MN OP QR ST will return the numeric kp * 1000 value
- 55 AA 01 69 - Request ki value
- 55 AA 05 69 MN OP QR ST - Returned message's MN OP QR ST will return the numeric ki * 1000 value
- 55 AA 01 64 - Request kd value
- 55 AA 05 64 MN OP QR ST - Returned message's MN OP QR ST will return the numeric kd * 1000 value
- 55 AA 01 65 - Request encoder value
- 55 AA 05 65 MN OP QR ST - Returned message's MN OP QR ST will return the numeric encoder * 1000 value
- 55 AA 01 53 - Stop PWM output
- 55 AA 01 52 - Resume PWM output