sampling two analog

RE: sampling two analog

Jared — Wed, 16 Jun 2021 12:49:10 GMT

[quote user="lyrics"]So, what is role of SAADC_CH_CONFIG_GAIN_Gain1_4 and SAADC_CH_CONFIG_REFSEL_VDD1_4 ?[/quote]

They are the configured Gain and Reference that is used during the sampling. Please read the product specification regarding this topic, and consider making a new ticket for future problems as the original problem has been solved.

regards

Jared

RE: sampling two analog

lyrics — Tue, 15 Jun 2021 01:21:34 GMT

Hi, I fixed the issue.. But another question.

I reference this github code, and followed the code like this.

    nrf_saadc_channel_config_t cds_channel_config =
    NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);

    cds_channel_config.gain = NRF_SAADC_GAIN1;

    nrf_saadc_channel_config_t co_channel_config =
    NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN6);

    co_channel_config.gain = NRF_SAADC_GAIN1;

    err_code = nrf_drv_saadc_init(&cds_saadc_config, cds_saadc_callback);
    if(err_code != NRF_SUCCESS) return 1;

    err_code = nrf_drv_saadc_channel_init(0, &cds_channel_config);
    APP_ERROR_CHECK(err_code);
    if(err_code != NRF_SUCCESS) return 1;

    err_code = nrf_drv_saadc_channel_init(1, &co_channel_config );
    APP_ERROR_CHECK(err_code);
    //if(err_code != NRF_SUCCESS) return 1;

    err_code = nrf_drv_saadc_buffer_convert(m_cds_buffer_pool[0], 1);
    APP_ERROR_CHECK(err_code);
    //if(err_code != NRF_SUCCESS) return 1;

    err_code = nrf_drv_saadc_buffer_convert(m_cds_buffer_pool[1], 1);
    APP_ERROR_CHECK(err_code);

and then it works well, but the result of data are not what I expected.

So, what is role of SAADC_CH_CONFIG_GAIN_Gain1_4 and SAADC_CH_CONFIG_REFSEL_VDD1_4 ?

RE: sampling two analog

lyrics — Mon, 14 Jun 2021 06:05:52 GMT

Hi,

[quote userid="73165" url="~/f/nordic-q-a/76130/sampling-two-analog/314864#314864"]OK, but this is a different function than earlier. What error code is returned?[/quote]

In that case, the err_code is 0x11 (17).

However, if I move on to the next function with the break point, the error below occurs.

RE: sampling two analog

Jared — Fri, 11 Jun 2021 09:10:29 GMT

[quote user="lyrics"]

But error occurs second channel init function.. (nrf_drv_saadc_channel_init)

[/quote]

OK, but this is a different function than earlier. What error code is returned?

regards

Jared

RE: sampling two analog

lyrics — Fri, 11 Jun 2021 07:23:25 GMT

Hi,

[quote userid="73165" url="~/f/nordic-q-a/76130/sampling-two-analog/314633#314633"]Maybe it would be better to just use 10 bits in both cases, [/quote]

First of all, I just added a channel and ran the program..

But error occurs second channel init function.. (nrf_drv_saadc_channel_init)

I hope there is reference code (example)!

    ret_code_t err_code;
    nrf_drv_saadc_config_t cds_saadc_config;

    cds_saadc_config.low_power_mode = false;                                  //Enable low power mode.
    cds_saadc_config.resolution = NRF_SAADC_RESOLUTION_8BIT;                  //Set SAADC resolution to 12-bit. This will make the SAADC output values from 0 (when input voltage is 0V) to 2^12=4096 (when input voltage is 3.6V for channel gain setting of 1/6).
    cds_saadc_config.oversample = NRF_SAADC_OVERSAMPLE_DISABLED;              //Set oversample to 4x. This will make the SAADC output a single averaged value when the SAMPLE task is triggered 4 times.
    cds_saadc_config.interrupt_priority = APP_IRQ_PRIORITY_LOW;               //Set SAADC interrupt to low priority.

    nrf_saadc_channel_config_t cds_channel_config =
    NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);

    err_code = nrf_drv_saadc_init(&cds_saadc_config, cds_saadc_callback);
    if(err_code != NRF_SUCCESS) return 1;

    err_code = nrf_drv_saadc_channel_init(0, &cds_channel_config);
    if(err_code != NRF_SUCCESS) return 1;

    err_code = nrf_drv_saadc_buffer_convert(m_cds_buffer_pool[0], 1);
    APP_ERROR_CHECK(err_code);
    
    err_code = nrf_drv_saadc_buffer_convert(m_cds_buffer_pool[1], 1);
    APP_ERROR_CHECK(err_code);
    
    nrf_saadc_channel_config_t co_channel_config =
    NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN6);

    err_code = nrf_drv_saadc_channel_init(1, &co_channel_config );
    APP_ERROR_CHECK(err_code);
    
    err_code = nrf_drv_saadc_buffer_convert(m_co_buffer_pool[0], 1);
    APP_ERROR_CHECK(err_code);
    
    err_code = nrf_drv_saadc_buffer_convert(m_co_buffer_pool[1], 1);
    APP_ERROR_CHECK(err_code);
    
    //CDS_F=1;
    return 0;

RE: sampling two analog

Jared — Thu, 10 Jun 2021 08:57:34 GMT

Hi,

[quote user="lyrics"]

Because I set different resolution value. cds is 8Bit , and co is 10Bit. Also, I tried to handle each value

[/quote]

Then you need to:

Initialize the SAADC with 8 bit resolution.
Sample
Un initialize the SAADC
Initialize the SAADC with 10 bit resolution
Sample

Maybe it would be better to just use 10 bits in both cases, that way you wouldn't need to reinitialize the SAADC peripheral between each sample. You can truncate the 10 bit result to 8 bit in your application instead.

[quote user="lyrics"]Is there a way to separate two channels in one handler? [/quote]

The samples are taken sequential starting from the lowest channel number. You can print the number of the sample to keep track of which channel it comes from. For example, if you're using two channels then you know that odd numbered samples are from the first channel, and even numbered samples are from the second channel.

regards

Jared

RE: sampling two analog

lyrics — Thu, 10 Jun 2021 00:17:06 GMT

[quote userid="73165" url="~/f/nordic-q-a/76130/sampling-two-analog/314413#314413"]But do they require a different configuration of the SAADC peripheral? If yes, exactly what needs to be different? [/quote]

Because I set different resolution value. cds is 8Bit , and co is 10Bit. Also, I tried to handle each value

with a handler. (cds_handler and co_handler)

I don't know the ads functions well, so I just divided them into two.

Is there a way to separate two channels in one handler?

RE: sampling two analog

Jared — Wed, 09 Jun 2021 09:35:26 GMT

But do they require a different configuration of the SAADC peripheral? If yes, exactly what needs to be different?

[quote user="lyrics"]it returns 0x08 error , second initializing[/quote]

Yes, as I suspected, the issue is that you try to initialize the driver after it has already been initialized. You need to un initialize it in between if you want to use a different config for the SAADC driver.

Error 0x08 = NRF_ERROR_INVALID_STATE

RE: sampling two analog

lyrics — Wed, 09 Jun 2021 08:50:53 GMT

[quote userid="73165" url="~/f/nordic-q-a/76130/sampling-two-analog/314385#314385"]Exactly what error occurs?[/quote]

it returns 0x08 error , second initializing.

 err_code = nrf_drv_saadc_init(&co_saadc_config, co_saadc_callback);

[quote userid="73165" url="~/f/nordic-q-a/76130/sampling-two-analog/314385#314385"] Is there any difference between cds_saadc_config and co_saadc_config? [/quote]

they are different sensor, so each sensor value needs to sampling.

RE: sampling two analog

Jared — Wed, 09 Jun 2021 08:33:32 GMT

Hi,

Exactly what error occurs?

The SAADC periperhal should only be initialized once with the same nrfx_saadc_config_t configuration.

You can un-initialize it and then re-initialize with a new configuration. Is there any difference between cds_saadc_config and co_saadc_config?

The channels can be configured differently so this shouldn't be a problem.

regards

Jared