topic Re: ADC Conversion in MPC5xxx

ADC Conversion

kajolvarma — Wed, 25 Sep 2019 06:35:52 GMT

We have written code for eQADC_A in mpc5777c and set to 1.2Msps (verified using input sine wave and plotting graph of it).

In eQADC_A we are using continuous scan method, with software pit3 as trigger source of 20.8us and use of DMA to request data from rfifo to the system memory.

For 50Hz input sine wave with pit3 timer practically 480 samples are used instead of 960 samples which is calculated as theortically.

For 10KHz input sine wave with same pit3 timer, 5 samples are required.In order to increase the number of samples, we have used timer of 2us for 50 samples .But we are unable to obtain samples for 10KHz.

Re: ADC Conversion

davidtosenovjan — Thu, 03 Oct 2019 11:11:39 GMT

Hi,

I don't understand too much mention about 20.8us PIT trigger. Continuous scan just expected ADC conversions run continuously i.e. it is triggered once.

Another point is whether you are using both converters simultaneously (ADC0 and ADC1) what's precondition of achieving of maximum sampling rate.

Re: ADC Conversion

kajolvarma — Fri, 11 Oct 2019 15:04:04 GMT

We are using pit tigger for DMA operation.Yes we are using ADC0 and ADC1 alternately.

Re: ADC Conversion

davidtosenovjan — Mon, 14 Oct 2019 11:11:44 GMT

This is incorrect indeed.

Result draining needs to be trigger by eQADC itself, DMA channels 1, 3, 5. 7, 9 and 11.