12 bit ADC DMA Filter DMA UART

[dhgac_296796]

I am trying to configure 12 bit delta sigma ADC for transferring analog data to filter via DMA. I had to set 12 bit resolution to match the sample rate of ADC and filter. It is required to send higher byte of data to UART for serial communication. However I am not getting data..Please suggest for possible solutions..

[odissey1]

Make sure that ADC coherency settings are correct (screenshot attached)

[odissey1]

Ups, just noticed you need 12-bit, not 16. 

[dhgac_296796]

Thanks for your time!! I have referred to the ADC and Filter coherency settings given for 9-16 bit adc resolution. Please go through the attachment for correction if any..

I am using two DMA channels for data transfer, one for ADC to filter and second for Filter to UART/DAC8. Getting no hint if filter output received at the UART will be in 2's complement format and how can I get it corrected for my signal? 

[odissey1]

There are issues with Filter-DMA-VDAC, see this thread

Class D adcDelSig>Filter>Pwm using DMA only

So I recommend using Filter-driven interrupt approach. To convert data then you simply need to add 128u to Filter result. See Cypress Filter example.

Other thing is that UART can't handle more than 1-3 ksamples/sec at 115kb anyway, so interrupt-driven approach is totally sufficient.

[dhgac_296796]

Thanks for the guideline.

I had tried the interrupt driven approach earlier for 8bit data. For 8 bit ADC resolution I had added 128u to filter result, for 16bit resolution I had added 65536u. I was unable to get 1100 samples/second in ADC for 8 bit or16 bit resolution. I am using single sample mode. This is required for filter sample rate requirement. Hence I moved to 12 bit resolution. 

But I don't understand how filter will work on 2 byte data with 12 ADC bit resolution..

[odissey1 · Accepted solution]

I probably don't understand the issue. The filter does not care about input rate, if you have e.g. 2 kHz, just specify it in filter dialog. If 1100 Hz is absolutely necessary, you can get it using ADC external trigger mode (soc attached to 1100Hz  clock or PWM).