I want to read two values at the same time through saadc.

Question

Hello

I want to read the values of two potentiometers from the Ain0 pin and the Ain1 pin through SAADC.

I could easily read one value through the saadc example, but I don't know how to add more.

APP_PWM_INSTANCE(PWM1,1);

#define SAMPLES_IN_BUFFER 5
volatile uint8_t state = 1;
static volatile bool ready_flag;            // A flag indicating PWM status.

static const nrf_drv_timer_t m_timer = NRF_DRV_TIMER_INSTANCE(0);
//static const nrf_drv_timer_t m_timer2 = NRF_DRV_TIMER_INSTANCE(1); //add
static nrf_saadc_value_t     m_buffer_pool[2][SAMPLES_IN_BUFFER];
static nrf_ppi_channel_t     m_ppi_channel;
static uint32_t              m_adc_evt_counter;


void pwm_ready_callback(uint32_t pwm_id)    // PWM callback function
{
    ready_flag = true;
}


void timer_handler(nrf_timer_event_t event_type, void * p_context)
{

}


#define ADC_TIME  100

void saadc_sampling_event_init(void)
{
    ret_code_t err_code;

    err_code = nrf_drv_ppi_init();
    APP_ERROR_CHECK(err_code);

    nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
    timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_32;
    err_code = nrf_drv_timer_init(&m_timer, &timer_cfg, timer_handler);
    APP_ERROR_CHECK(err_code);

    /* setup m_timer for compare event every 400ms */
    uint32_t ticks = nrf_drv_timer_ms_to_ticks(&m_timer, ADC_TIME);
    nrf_drv_timer_extended_compare(&m_timer,
                                   NRF_TIMER_CC_CHANNEL0,
                                   ticks,
                                   NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                   false);
    nrf_drv_timer_enable(&m_timer);

    uint32_t timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&m_timer,
                                                                                NRF_TIMER_CC_CHANNEL0);
    uint32_t saadc_sample_task_addr   = nrf_drv_saadc_sample_task_get();

    /* setup ppi channel so that timer compare event is triggering sample task in SAADC */
    err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_assign(m_ppi_channel,
                                          timer_compare_event_addr,
                                          saadc_sample_task_addr);
    APP_ERROR_CHECK(err_code);
}


void saadc_sampling_event_enable(void)
{
    ret_code_t err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);

    APP_ERROR_CHECK(err_code);
}


uint16_t pwm_period;

void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{
    int16_t adc_value = 0; //0 ~ 550
    int16_t adc_value2 = 0; //0 ~ 550
    int16_t pwm_value = 0; //35 ~ 55kHz
    int16_t duty_value = 0; // 0 ~ 100

    if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
    {
        ret_code_t err_code;

        err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);

        int i;
        //NRF_LOG_INFO("ADC event number: %d", (int)m_adc_evt_counter);

        for (i = 0; i < SAMPLES_IN_BUFFER; i++)//output 5times
        {
            //NRF_LOG_INFO("%d", p_event->data.done.p_buffer[i]);
            adc_value += p_event->data.done.p_buffer[i]; //adc adverage
        }
        m_adc_evt_counter++;
        adc_value /= SAMPLES_IN_BUFFER; //abc adverage

        NRF_LOG_INFO("ADC1 value : %d", (int)adc_value); //OK
        NRF_LOG_INFO("ADC2 value : %d", (int)adc_value2); //Fail
    }

    pwm_value = adc_value * 10 / 550 + 18;  //map() : (adc_value - 0) * (28 - 18) / (550 - 0) + 18, (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min

    //pwm period : 18~28
    /*if(pwm_value > 28)
    {
      pwm_value = 28;
    }

    else if(pwm_value < 18)
    {
      pwm_value = 18;
    }*/

    pwm_period = pwm_value;
    NRF_LOG_INFO("PWM period : %d", (int)pwm_period);
}


void saadc_init(void)
{
    ret_code_t err_code;

    nrf_saadc_channel_config_t channel_config =
        NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);

    nrf_saadc_channel_config_t channel_config2 = //add
        NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);

    err_code = nrf_drv_saadc_init(NULL, saadc_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_channel_init(1, &channel_config2); //add
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0], SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1], SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);

}

Can I get some advice on this?

Thank you.

=================================================================

(Edit)

The value of adc is outputting strangely.
Reading the adc value of the potentiometer, the value is printed as shown below.

<info> app: ADC1 value : 470

<info> app: ADC1 value : 388

<info> app: ADC1 value : 469

<info> app: ADC1 value : 387

<info> app: ADC1 value : 467

<info> app: ADC1 value : 388

<info> app: ADC1 value : 467

<info> app: ADC1 value : 387

<info> app: ADC1 value : 470

<info> app: ADC1 value : 387

Like this, the adc value has up and down repeatedly. I am calculating the pwm period using the value of adc. But because of this problem, the pwm is output strangely.

And the potentiometer ranges from about 0 to 600. Is this the right value?

Thank you.