Hello guys,
I am reading the source code, trying to figure out how odrive works, and planning to do some modifies for my own project.
today I stucked here:
ControlLoop_IRQHandler(void) {…} // in board.cpp
I realize this is the core loop of the FOC algrithm. However, I don’t figure out how this IRQ is called.
Though, I found this “ControlLoop_IRQHandler” is a definition of “OTG_HS_IRQHandler”
" #define ControlLoop_IRQHandler OTG_HS_IRQHandler #define ControlLoop_IRQn OTG_HS_IRQn
"
Then I googled OTG_HS_IRQ, turns out “OTG_HS” is a USB interrupt .
I am very confused!
What is the relationship of Controlloop and an USB interrupt !? and when is this function called?
By my understanding: kinda core loop should be synchronized with PWM, and always called by a Timer IRQ.
It’s called in board.cpp - the NVIC “Software Triggered Interrupt Register” NVIC->STIR is set from a timer, this seems to be a hack to switch interrupt priority from high (timer IRQ) to low (USB IRQ).
The OTG_HS_IRQ interrupt is not being used for USB - it’s just being used as a spare low-priority interrupt slot to run the control functions.
Thank you for the explaination. This explains most things, just some detail not very clear:
Why ControlLoop has the lowest priority among those interrupts?
I understand that the data updates happens after hardware sampling, but seems
“fetch_and_reset_adcs” & “measure current” are functions of “ControlLoop” it self. I feels little tangled.
P.S. control_loop_cb, what here this surfix “cb” refers? what does those functions end with “_cb” in commom?
_cb stands for ‘callback’ - i.e. a function called in a foreign context
The timer interrupts themselves must have the highest priority since they run the PWM outputs - we don’t want the PWM to be stuck, because if that happens it could cause smoke. Similarly the ADCs are running via DMA and they are highly timing sensitive - they run in the background at a higher priority than all but the PWM timers.
The control loop reads from the ADC and writes to the PWM, and has a higher priority than all of the RTOS threads, but lower than the timers and ADCs. At least that is my understanding.
that’s very clear! That verifies most of my concerns. cool, thank you.