STM32F4 Discovery: Trying to trigger ADC conversion with Timer, How to Debug?

Posted on December 05, 2012 at 21:58

8 KHz is going to be a bit of a bugger to do by eye.

You could look at the TIM channel outputs directly on the pins with a scope.

You could reflect register bits to external pins/LEDs.

You could catch the EOC interrupt from the ADC, toggling a pin in response.

You could DMA out of the ADC into memory, and park a memory view/watch window over it.

You could output telemetry via the serial port. Monitoring locations, registers, counts, etc.

Posted on December 05, 2012 at 22:36

Thanks for that quick response!  I've verified my timer is firing at 8 kHz by toggling an LED in the timer interrupt handler and putting a scope on it. Yes, I know that means my LED is blinking at 4 kHz ;) 

Your list of suggestions got me thinking of some things to try out.

Quick question on your serial port comment...can I just printf and have info appear in my IDE console? From what I understand, ARM debugging used properly can be quite powerful, and printf's are the clear sign of King N00b, but if its a starting point, whatever works works.

Thanks again.

Posted on December 06, 2012 at 01:53

Well you can certainly retarget the printf/putchar functions to use a serial port. The ARM9 parts had a DCC (Debug Com Channel), and the M3 has a SWV, although I've had kind of mixed results with the latter, and support for it on various debug pods.

http://www.keil.com/download/files/swv_on_cortex-m3.pdf

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See also retarget.c and serial.c examples in some of Keil's sample directories.

Posted on December 06, 2012 at 18:05

Cool, thanks again.

BTW, got my issue sorted out. EXTEN[1:0] was never getting set correctly, thereby disabling any external triggering. Looked around a bit thru the ST Library docs and couldn't really find what function/struct parameter sets those bits. Oh, the perils of using someone else's library! :D