Reading ADC with a double buffer

RE: Reading ADC with a double buffer

Edvin — Mon, 30 Apr 2018 09:38:19 GMT

Did you measure the same source with all three pins, or was channel 1 measuring something else?

What chip do you use? nRF52832 or nRF52840?

And you say that you used SDK14. Is that SDK14.0.0, SDK14.1.0 or SDK14.2.0?

BR,

Edvin

RE: Reading ADC with a double buffer

Alaa — Sun, 29 Apr 2018 05:34:21 GMT

Hi Edvin,

Yes, channel_config settings for 0,1,2 were the same like appears in the code I posted.

And about oversampling, I just changed the variable SAADC_CONFIG_OVERSAMPLE in sdk_config.h to 2. Do I have to do anything else to turn it on correctly?

Thanks!

RE: Reading ADC with a double buffer

Edvin — Thu, 26 Apr 2018 14:17:33 GMT

Oversampling should not cause a higher value. When the error occured, did you have oversampling on all the channels, or only one of them? And in addition to oversampling, was the rest of the channel_config settings the same?

Best regards,

Edvin

RE: Reading ADC with a double buffer

Alaa — Thu, 26 Apr 2018 08:24:41 GMT

3 different GPIOS (AIN0, AIN1, AIN2). And here's the initialization:

    nrf_saadc_channel_config_t channel_0_config =
        NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);
    channel_0_config.gain = NRF_SAADC_GAIN1_6;
    channel_0_config.reference = NRF_SAADC_REFERENCE_VDD4;
	
    nrf_saadc_channel_config_t channel_1_config =
        NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);
    channel_1_config.gain = NRF_SAADC_GAIN1_6;
    channel_1_config.reference = NRF_SAADC_REFERENCE_VDD4;
	
    nrf_saadc_channel_config_t channel_2_config =
        NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN2);
    channel_2_config.gain = NRF_SAADC_GAIN1_6;
    channel_2_config.reference = NRF_SAADC_REFERENCE_VDD4;
	
    err_code = nrf_drv_saadc_init(&saadc_config, saadc_callback);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_channel_init(0, &channel_0_config);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_saadc_channel_init(1, &channel_1_config);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_saadc_channel_init(2, &channel_2_config);
    APP_ERROR_CHECK(err_code);

I just disabled OVERSAMPLING and now it's working well. Each channel looks independent now. Is there a way to make it work with oversampling enabled? Why would oversampling (of 4x) cause this behavior?

Thanks

RE: Reading ADC with a double buffer

Edvin — Wed, 25 Apr 2018 12:38:52 GMT

Hello,

Do you have 3 different gpios measureing these values? Are they connected/shorted to anything? Or do you have one input GPIO, and it stores the values into three different sections in the buffer?

Best regards,

Edvin