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Input Capture Triggered ADC Measurements

Question asked by Jeremy Hubbard on Sep 19, 2012
Latest reply on Sep 21, 2012 by Jeremy Hubbard

I would like to sample an arbitrary waveform from a function generator synchronously to the sync output while timing the period of the sync.  To do this I have the input capture set to do a hardware trigger for the ADC which then does a series of measurements which are copied to RAM with the DMA.  In order to time the sync I have the prescale set to 1 which makes the FTM overflow often, so I also used the Global Time Base to synchronize 2 FTM's so that I could separate the ISR for the overflow from the input capture event ISR.

 

The problem I am having is that I am getting a hardware trigger from the FTM for the ADC when the timer overflow occurs.  Is there a way to stop this from happening?  Or will I need to do something different, such as have the input capture trigger the PDB which triggers the ADC, but even then I would assume I would see the same issue I am having.  In the end I would like to have a very repeatable delay from the Input capture event to the start of the ADC's measurement cycle.

 

I am using the TWR-K40X256 with Codewarrior 10.2.

 

Thanks,

Jeremy

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