Hi
I want to perform periodic ADC reads on multiple channels. I’d like to collect several samples of the same channel prior to interrupting CPU, multiple channels simultaneously. PCB is done already; both ADC0 and ADC1 will sample about 5-6 channels. Please fix my thoughts or suggest better solution.
I place destination buffer at 2^DMA.TCD.DMOD aligned location. DMA.TCD.NBYTES is 4*8 (8 channels instead of 5-6 required, but major DMA loop aligns with DMOD) after N samples.
Since DMA.TCD.SLAST applies to major loop, I can’t use it the way I want. Using SLAST is fine for single sample (snapshot of) of multiple ADC channels and DMA interrupt after each sample. For interrupt after multiple samples, I need to use DMA source address modulo (SMOD) feature and use ADC registers starting from one, which is SMOD aligned. SMOD should be 5, 2^5=32 = 8 samples * sizeof(ADC register). Unfortunately ADC RA register is not 32 bytes aligned. Instead of using ADC result registers RA-RH (offsets 0x48..0x67), it seems I need to use RG-RN (offsets 0x60..0x7F).
Is above correct or am I’m complicating something? I managed to make PDB in BB+CONT mode triggering periodic ADC samples, but using DMA SLAST instead of SMOD, so interrupt after every sample. I hope PDB won’t show stop interrupt every Nth sample.
Edward
