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Battery level detect in nRF52832

Hi,

Does nRF52832 use normal ADC input to detect battery level (ex. AIN0, AIN1...)? or nRF52832 have other method to do this job?

Thank you,

Chianglin

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  • Hi,

    If I want to use two ADC at the same time, one for "ADC Sensor input", and the other one for "Battery level detect".  How can I modify following source code?

    void saadc_init(void)
    {
        ret_code_t err_code;
    
    	// ---------- Initialize ADC for Pressure-Sensor ----------------
    	// 變更 ADC 的 bit 數
    	nrf_drv_saadc_config_t saadc_config = NRF_DRV_SAADC_DEFAULT_CONFIG;
    	saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT;
    
        nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);
        // 變更 ADC 倍率 & 參考電壓
    	channel_config.gain = NRF_SAADC_GAIN1_4;
    	channel_config.reference = NRF_SAADC_REFERENCE_VDD4;
    
    	err_code = nrf_drv_saadc_init(&saadc_config, saadc_Sensor_callback);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_channel_init(0, &channel_config);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0], SAADC_SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1], SAADC_SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);
    
    	// ---------- Initialize ADC for Battery detect ----------------
    #if 1
        err_code = nrf_drv_saadc_init(NULL, saadc_Battery_event_handler);
        APP_ERROR_CHECK(err_code);
    
        nrf_saadc_channel_config_t config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_VDD);
        err_code = nrf_drv_saadc_channel_init(0, &config);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_buffer_convert(m_battery_adc_buf[0], SAADC_SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_buffer_convert(m_battery_adc_buf[1], SAADC_SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);
    #endif
    }

    System will crash when "second nrf_drv_saadc_init() execute".

    Thank you

  • Hi,

    chianglin said:
    System will crash when "second nrf_drv_saadc_init() execute".

    That is expected. You should only initialize the driver once unless you disable it in between (for instance to save power). So you should remove the second call to nrf_drv_saadc_init(), and use a common event handler for both. If you sample either one or the other, you will know which it is based on what you just sampled. If you sample both at the same time, you will know based on the order. (sampling both at the same time may not be that useful since you probably don't need battery information as often as you need sensor input).

    chianglin said:
    If I want to use two ADC at the same time, one for "ADC Sensor input", and the other one for "Battery level detect".  How can I modify following source code?

    To sample both channels in consecutive order, just enable the second channel as well, and make sure the result buffer is a multiple of the number of channels. If you want to sample either one or the other, and both at a low rate, then it is most power-efficient to configure sampling of the first channel (sensor), do that, and then uninitialized the SAADC. Then do the same when it is time to sample the other channel (VDD).

  • Hi,

    According to your instructions, does follow source code is correct?

    void saadc_init(void)
    {
        ret_code_t err_code;
    
    	// Modify ADC resolution
    	nrf_drv_saadc_config_t saadc_config = NRF_DRV_SAADC_DEFAULT_CONFIG;
    	saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT;
    
    	// Initialize ADC
    	err_code = nrf_drv_saadc_init(&saadc_config, saadc_callback);
        APP_ERROR_CHECK(err_code);
    
    	// ---------- Initialize ADC for Pressure-Sensor ----------------
        nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);
    	channel_config.gain = NRF_SAADC_GAIN1_4;
    	channel_config.reference = NRF_SAADC_REFERENCE_VDD4;
    
        err_code = nrf_drv_saadc_channel_init(0, &channel_config);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0], SAADC_SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1], SAADC_SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);
    
    	// ---------- Initialize ADC for Battery detect ----------------
        nrf_saadc_channel_config_t config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_VDD);
        err_code = nrf_drv_saadc_channel_init(1, &config);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_buffer_convert(m_battery_adc_buf[0], SAADC_SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_drv_saadc_buffer_convert(m_battery_adc_buf[1], SAADC_SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);
    }
    

    How can I modify saadc_callback() function to read two different ADC channel?

    Would you please give me a “saadc_callback()" sample code?

    Thank you

  • Hi,

    Yes, I can try to put together a simple example. But then it would be good if you can clarify a few things first:

    • Should both the battery and sensor be sampled simultaneously all the time, or should one be sampled more often than the other?
    • Should one/both be sampled regularly, or sampled by SW at arbitrary times?
    • Any other info on what behavior you need?
  • Hi,

    Thank you for your support.

    About your question.

    1. As your description of previous mail, the sampling rate of battery don't need very fast, but 糸he sampling frequency of the sensor is as fast as possible.

    2. Yes, one/both should be sampled regularly.

    Thank you again.

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