Interfacing the ADS7881 to TMS320C6713 DSP

Hi BAS,

That code you have for the ADS7881 takes 2048 samples and then halts the collection of data.  At that point it also stops the timer.  A simple way to verify that the timer is actually running is to remove the ADS7881EVM from the 5-6K Interface Board.  Move the little shunt jumper on J13 to the far right (for safe keeping).  Probe the timer output and you should see a 4MHz pulse stream.

Hi TOM,

Thanks for your reply.

Yes, I see pulse stream  at J14 (TOUTa) but why it doesn't have sample values ? dataPing and dataPong buffer has zero values and the program doesn't halt after taking 2048 samples, rather it doesn't halt at all and then I had to stop it in the end.

What should be done to make it work propoerly with PING PONG scheme ?

Thanks.

Hi TOM,

I am still waiting for you help.

In the user guide 'Interfacing ADS7881 to TMSC320C6713', it says to change the link handle in edmaCfgChan7A to hEdmaTbl7, instead of hEdmaTbl0 to continuously ping-pong between the two buffer. I did this but even then nothing is there in the buffer except Zeros.

Waiting for your help.

Hi BAS,

Did you wire the TIMER into W2?  You have to add a jumper from P2.17 to W2.2.

Hi TOM,

Yes I wired P2.17 to W2.2. Infact I am using the same setting used for the project you gave me before some time.

Hi BAS,

Not sure what to tell you here.  Can you please go back to the 'easy' program and verify that the setup works.  From there, double check the jumper settings on the two boards to make sure they match the description in the preamble to the main.c in the slaa257 document.  This might be a CE space issue - verify the jumper from W6 on the 5-6K interface board is properly set.

Hi TOM,

I checked 'easy' version of the program and it's working fine.

I did the changes according to slaa257. It is now going inside the hwiDMA_isr() function and writing to the buffers. I checked buffers value for dataPing and dataPong, both has 4095 value for 2048 size buffers (just a straight line if draw graph). The program doesn't run continue even after changing the link handle in edmaCfgChan7A to hEdmaTbl7, instead of hEdmaTbl0 as said by slaa257.

It is still not sampling right. What shoul I do now ?

Hi BAS,

Simply changing the link won't get the ping-pong buffer working.  The code will still kick you out after one collection cycle.  I am out of the country for the next two weeks and won't be able to provide you with anything specific to the ADS7881.  I will look around though and see if I can find a true ping-pong implementation example that you might be able to adapt on your own.

Hi TOM,

Thanks for your valuable help.

I will wait for your reply and have a nice journey.

Hi TOM,

If you are back, can you help me with real PING PONG program made for ADS7881 as we you told in your last message ?

Looking forward for your reply.

Hi BAS,

Sorry, but I talked with the author of that original code and he does not have the original ping-pong implementation of that code any longer.  Best I can do is offthe the attached example that used two different parts, one DAC and one ADC, to capture/store/transmit data through two McBSP ports using DMA.  I hope you find it useful.

Thanks TOM.