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adsp-bf707 using the eppi in general purpose mode

Question asked by mr_smithJohn on Mar 11, 2015
Latest reply on Mar 18, 2015 by Prashant



Here is my problem.  I am trying to set the EPPI (enhanced parallel port interface) up in general purpose mode so I can use it to transmit parallel data.  I have it working for the most part (i have the proper data coming across the lines, the frame syncs are behaving in the active low configuration, etc.) however I cannot seem to figure out what causes the interrupt to trigger the call back function.  It appears that upon submitting my initial buffer (prior to enabling the EPPI) the first interrupt gets called 5 frame syncs after the tx starts.  for example, if I submit 32 bytes, the first time the frame sync goes low I see the first byte of the data as expected, the second time, i see the second byte as expected, and so on... After I see the 5th byte on the logic analyzer, the interrupt triggers the callback, and the data continues coming in for all 32 bytes, which is fine since this is just the initial setup buffer and I do not care about the interrupt here. 


The problem is here:

For every buffer I go to submit post-initial setup (aka the ones I am using in my program to transmit data through the eppi) it appears the interrupt gets generated every 36 frame syncs.  Why?  If I send 32 bytes of data, and the interrupt is supposed to trigger on DMA Processed, why isnt the interrupt getting called at the appropriate time?


Does anyone have an example of working EPPI setup code for simple data transfers in TX mode?  If so could you please share?


Your assistance is greatly appreciated!