This is a minimal Rust program for the Raspberry Pi Pico that sets up a PWM channel and enables an interrupt handler for it. This program demonstrates that you must clear the PWM interrupt inside of the interrupt handler function or else the program will crash.
This program sends debug output to UART0 on pins 1 and 2 of the Pico, at 115200 baud. If you compile and run this program as-is, you should get output like this:
Hello from pico-pwm-irq-crash
t0: 14826 t1: 14832
t0: 14826 t1: 16407
t0: 14826 t1: 18224
t0: 14826 t1: 20047
t0: 14826 t1: 21870
t0: 14826 t1: 23692
t0: 14826 t1: 25515
t0: 14826 t1: 27338
t0: 14826 t1: 29161
t0: 14826 t1: 30984
t0: 14826 t1: 32807
t0: 14826 t1: 34629
t0: 14826 t1: 36452
... and the onboard LED will blink at 1Hz.
If you locate the these lines in src/main.rs:
// If you comment-out this line, this program will crash:
pwm.clear_interrupt();
and comment out the pwm.clear_interrupt() call, you will get output like this:
Hello from pico-pwm-irq-crash
t0: 14826 t1: 14832
t0: 14826 t1: 16407
t0: 14826 t1: 18224
t0: 14826 t1: 20047
t0: 14826 t1: 21870
t0: 14826 t1: 23692
t0: 14826 t1: 25515
t0: 14826 t1: 27338
t0: 14826 t1: 29161
t0: 14826 t1: 30984
t0: 14826 t1: 32807
t0
The output ends abruptly and incompletely, right around 20ms after the PWM was enabled and the handler function should have been called. The LED will not blink because the main program has crashed! This is because the PWM interrupt did not get cleared in the PWM interrupt handler function, and therefore the function will immediately be called again as soon as it exits -- forever.
For general info on Rust and RP2040/Raspberry Pi Pico programming: https://github.com/rp-rs/rp-hal
License for this repository: MIT