Arduino for STM32

if you get the same behaviors on multiple uarts, the code is probably more likely the source of your problem.

you probably want to figure out when stm32sd writes the time stamp in the directory, where it obtains the timing information and provide that from the rtc library.

you probably want to read the specific programming manual on your ARM core. general answers: 1. you can set priorities for different interrupts (there are code in the specific core_cmx.h files) for that. 2. a high priority interrupt (=interrupt with lower priority number) can preempt a low priority ...

usually very simple:

1. understand what the code is trying to do;
2. understand how it does on the original chip;
3. implement it on the target chip;
4. enjoy the fruit of your labor

but this could be easier said than done depending on what other parts of STM32DUINO need to be used in the final project. even when you use stm32duino cores, you can still write your own isr routines and toggle register bits... Is it really necessary to measure each and every cycle of the waveform ...

so if I uncomment "t1 = TIM1->CNT;", and re-run the code, t1 goes down to 23 - 25. I tested on a stm32f103: t0: always 0-> isr is triggered when the TIM1 rolls over to 0. t1: 19 ticks. quite close to the ARM specification (of 12 ticks minimum). t2: 133 ticks. meaningfully above my estimate earlier ...

I would be interested to see what you find. a couple differences that I can see: 1. my code doesn't rely on the stm32duino core(s): it uses a version of stm32duino-like core that I wrote myself and it is very lightweight and much faster. 2. in my test, I even pared down my code base to a customized ...

to further speed up the isr execution, you can move the pwm period / dc calculation out of the isr and into the main loop -> it has its own downside but I was able to reduce the isr execution time from just over 100 ticks to just shy of 70 ticks, inclusive of the isr latency. void pwm_tks(void ...

I then printed out t0 (should always be zero), t1 (~52 - 53) and t2 (103 - 104).

the equivalent of those numbers on a dsPIC33 (I happened to have it in front of me) would be t0 (always 0), t1 (~21), and t2 (~37).

I looked up ARM's documentation and it says that CM0 isr latency can be as low as 16 ticks (vs. low 20s I got), and CM3 isr latency can be as low as 12 ticks.