cc2538 ADC zstack

AMIT KUMAR13

Expert 1940 points

Other Parts Discussed in Thread: CC2538, Z-STACK

hi,

I am working in ADC in zstack on cc2538 controller

with the below code written

adc_digital_value=HalAdcRead ( HAL_ADC_CHN_AIN5,HAL_ADC_RESOLUTION_8);

I am always getting a value of 0-127 (instead of 0-255).

I am only getting 7 bit resolution with 8 bit resolution set.

Can anyone help me in this I tried to debug a lot but not getting the problem.

AMIT

over 9 years ago

0 YiKai Chen over 9 years ago

Guru 735585 points

Yes, it's 7 bits. You can refer to chapter 15 ADC in CC2538 user guide (www.ti.com/.../swru319c.pdf).

0 AMIT KUMAR13 over 9 years ago in reply to YiKai Chen

Expert 1940 points

so,
if i give HAL_ADC_RESOLUTION_8 i only get 7 bit resolution

so how can i get a 8 bit resolution in adc

0 Igor Sherer over 9 years ago in reply to AMIT KUMAR13

Guru 31280 points

Hi,

You can't get a 8-bit sample by using API, there are 7, 9, 10 and 12 bits options available.

The naming in Z-stack is an alias to actual sampling resolution.

0 YiKai Chen over 9 years ago in reply to AMIT KUMAR13

Guru 735585 points

Do you have special reason must to use 8 bit ADC resolution?

0 AMIT KUMAR13 over 9 years ago in reply to YiKai Chen

Expert 1940 points

Hi Y.Chen,
No, i am not having any special reason.I was only going through the ADC for CC2538.
Thanks

0 YiKai Chen over 9 years ago in reply to AMIT KUMAR13

Guru 735585 points

I see. According to datasheet and user guide, you can only use 7, 9, 10, and 12 bit resolution for CC2538 ADC.

0 Manuel Menchaca over 8 years ago in reply to YiKai Chen

Expert 2035 points

Yes, I think the HalAdcRead function should be updated because it's confusing:

  switch (resolution)
  {
    case HAL_ADC_RESOLUTION_8:
      reading >>= 8;
      break;
    case HAL_ADC_RESOLUTION_10:
      reading >>= 6;
      break;
    case HAL_ADC_RESOLUTION_12:
      reading >>= 4;
      break;
    case HAL_ADC_RESOLUTION_14:
    default:
      reading >>= 2;
    break;

And as we can read in the CC2538 User Guide, the resolutions are 7,9,10 and 12 bits (ENOB).

0 YiKai Chen over 8 years ago in reply to Manuel Menchaca

Guru 735585 points

I agree with you.

0 Manuel Menchaca over 8 years ago in reply to YiKai Chen

Expert 2035 points

Something like this should be the solution


switch (resolution)
{
  case HAL_ADC_RESOLUTION_7:
    reading >>= 9;
    break;
  case HAL_ADC_RESOLUTION_9:
    reading >>= 7;
    break;
  case HAL_ADC_RESOLUTION_10:
    reading >>= 6;
    break;
  case HAL_ADC_RESOLUTION_12:
  default:
    reading >>= 4;
  break;

0 YiKai Chen over 8 years ago in reply to Manuel Menchaca

Guru 735585 points

Anyway, you know it now to revise source code by yourself.

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