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Hi everyone,

does anybody have an approach to process a PWM-Signal from a sensor?

Mine looks like this at the moment:

Create 2 Tasks:

First one to poll the GPIO-Port which is connected to the PWM signal in 10µ-Second steps until end-condition is received, then suspend the task
Second one to wake first task in desired period time

I think getting an interrupt from the GPIO would be much more favorable.

Greets

Maybe the CPPM driver could give some ideas. It is using an input timer to take time stamps of GPIO transitions and then feeding that to a queue.

Thanks for your reply.

Could you explain to me, how the input timer works?

I've managed to catch an interrupt with the transition on my GPIO-Pin (IO_3 on board), but the system stops working at the moment the IRQ appears.
I think i am lacking of saving the context of FreeRTOS.

Unfortunately I did not completely understand your CPPM-Driver, but it seems, as you are skipping the part i tried to program.

How is it possible, to catch the Flanks directly and start the timers? I also think the timers are depending on which GPIO-Port one is using.
I couldnt figure out, with which timer i need to replace TIM14 in the code when using PB5 as input. Or should i just switch to PA7 (which i assume you use)?

Thanks in advance.


edit: Where can I find the define for NVIC_CPPM_PRI?

edit2: The code works. But i want to count from a falling edge to a rising edge. There are three modes, rising, falling and both. Is it possible in one interrupt to only count the low time of the pwm signal? or do i need two interrupts, one for starting the counter at falling edge and one stopping the counter at rising edge?

and the second problem is, that i get big noise problems. I attached a screenshot. before this measurement i selected falling edge mode.

edit3: selecting both edges on the interrupt capture did the trick. now i get proper distance reading from my sensor. but the peaks are still there. anyone has a clue?