[sdiy] dsPIC DMA RAM to DAC problem

[Tom Wiltshire]

I came across that video whilst trying to find a solution to my  
current problem; getting the DMA working shifting audio data from the  
dual-port SRAM to the audio DAC on the dsPIC 33FJ128GP802.

Has anyone got any experience doing this?

The audio DAC is pretty striaghtforward, and I've got DMA interrupts  
occurring every 16 samples. The fact this happens at the right speed  
means the DMA is getting interrupts from the DAC correctly.

I've stuck dummy data in the DPSRAM (The DMA RAM area) which is just  
a ramp going up and a ramp going down. If the DMA works correctly in  
ping-pong mode, I should see a triangle wave coming out at 1/32nd of  
the sample rate. But I'm not seeing any output from the DAC.

It's one of those evil register set-up problems which give you very  
little feedback and thereby make debugging very difficult.

Any help appreciated - I'm on my second day of this, and I'm just  
starting to get slightly annoyed. Assembly programmers need infinite  
patience!
Thanks,
T.