• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 82 subscribers
  • Views 275 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F28034: ADC: Initial Conversion, the first sample may not be the correct conversion result or discard?

Shaoxing Ke
Expert 3590 points
Part Number: TMS320F28034

Hi Experts,

I am asking for my customer here.

They are using 80 Pin F28034-PN to develop HVAC, and also found the following restriction here about ADC Initial Conversion.

Here is customer ADC code, they use EPWM1_SOCA to trigger sequential SOC0~SOC11 and SOC15, simultaneous they also use EPWM4_SOCB to trigger sequential SOC12, SOC13, and SOC14. So, according to the errata manual, the ADCRESULT0 and ADCRESULT12 will be missing or incorrect, Right? If yes, how far will the error go? 

Fullscreen
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
EALLOW;
AdcRegs.ADCCTL1.bit.RESET = 1;
asm(" NOP ");
asm(" NOP ");
AdcRegs.ADCCTL1.bit.ADCREFSEL = 0;
AdcRegs.ADCCTL1.bit.ADCBGPWD = 1;
AdcRegs.ADCCTL1.bit.ADCREFPWD = 1;
AdcRegs.ADCCTL1.bit.ADCPWDN = 1;
AdcRegs.ADCCTL1.bit.ADCENABLE = 1;
(*Device_cal)();
asm(" RPT#100 || NOP");
DELAY_US(ADC_usDELAY);
AdcRegs.ADCCTL1.bit.INTPULSEPOS = 0;
AdcRegs.ADCCTL2.bit.ADCNONOVERLAP = 1;
AdcRegs.ADCSOC0CTL.bit.ACQPS = 6;
AdcRegs.ADCSOC1CTL.bit.ACQPS = 25;
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

In a word, 80Pin F28034 only one ADC module has 16 Chanel, and ADC has only 16 SOC trigger signal, so if set the below sequential or simultaneous sampling mode, if the application calls for a given series of conversions, SOC0→SOC1→SOC2, to initiate periodically, then set up the series instead as SOC0→SOC1→SOC2→SOC3 and only use the last three conversions, ADCRESULT1, ADCRESULT2, ADCRESULT3, thereby discarding ADCRESULT0. Therefore, customer would waste some analog channel resources. Could you explain it in more detail about ADC: Initial Conversion? Or how to design to meet with customer's need up to 16 channel ADC sampling here. Thanks a lot!

  • 0
    TI__Mastermind 32436 points

    Hi Shaoxing,

    In the situation that you explained, ADCRESULT0 and ADCRESULT12 will be incorrect. I do not think we have documentation about how bad the first sample error will be since this will change for every scenario. 

    I do not think there is a clean way to use all 16 SOCs, they will just need to find a way to trigger the first SOC twice. For example, they could use an ADC interrupt that comes at the EOC of SOC0 to software trigger SOC0. 

    Best Regards,

    Ben Collier

  • +1 in reply to Benjamin Collier
    TI__Expert 3590 points

    Hi Ben,

    Got it, Very thanks for your comment.