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Using one discovery board as a signal generator and another as input capture

Question asked by mex1 on Nov 22, 2013
Latest reply on Nov 23, 2013 by fm
Hello, I've been attempting to set up two discovery boards. One as a signal generator that generates a 1 Hz pulse (50% duty cycle), and the other to accept that signal as input capture. I can't seem to get the input capture board to generate interrupts on the 1 Hz pulse though.

I'm getting stuck because it seems like both boards are configured correctly. I confirmed that the 1 Hz pulse is correct on an oscilloscope. For the input capture board, if I take a wire and plug one end onto a 3.3 V output pin, then tap the other end on the input capture pin, I can see that the interrupt is generated.

Despite working when tested separately, when I connect their grounds and then their respective pins together, it fails to generate any interrupts. An interesting symptom that I noticed is that when I measure the resistance between the input capture pin and its respective ground, I only get 10 Ohms, which strikes me as a red flag. 

Anyone have an idea what might be causing this?