52832 saadc Multi-channel acquisition

[muyang]

HI, When I use the SAADC example, I found that the data collected during the simultaneous 8-channel acquisition has abnormal data on both channels。

I've ported the SAADC program to it ：nRF5_SDK_12.3.0_d7731ad\examples\ble_peripheral\ble_app_uart\pca10040\s132\arm5_no_packs

#define SAMPLES_IN_BUFFER 8
volatile uint8_t state = 1;

static const nrf_drv_timer_t m_timer = NRF_DRV_TIMER_INSTANCE(3);
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 timer_handler(nrf_timer_event_t event_type, void * p_context)
{

}

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, 400);
    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);
}


void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{
    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\r\n", (int)m_adc_evt_counter);
		printf("ADC event number: %d\r\n", (int)m_adc_evt_counter);

        for (i = 0; i < SAMPLES_IN_BUFFER; i++)
        {
            //NRF_LOG_INFO("%d\r\n", p_event->data.done.p_buffer[i]);
			printf("%d\r\n", p_event->data.done.p_buffer[i]);

		}
        m_adc_evt_counter++;
    }
}


void saadc_init(void)
{
    ret_code_t err_code;
	
	nrf_drv_saadc_config_t saadc_config = NRF_DRV_SAADC_DEFAULT_CONFIG;
    saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT;
	
    err_code = nrf_drv_saadc_init(NULL, saadc_callback);
    APP_ERROR_CHECK(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_config1 =
	NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);

	nrf_saadc_channel_config_t channel_config2 =
	NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN2);
	
	nrf_saadc_channel_config_t channel_config3 =
	NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN3);
	
	nrf_saadc_channel_config_t channel_config4 =
	NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN4);


	nrf_saadc_channel_config_t channel_config5 =
	NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN5);
	
	nrf_saadc_channel_config_t channel_config6 =
	NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN6);


	nrf_saadc_channel_config_t channel_config7 =
	NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN7);


	err_code = nrf_drv_saadc_channel_init(0, &channel_config);
    APP_ERROR_CHECK(err_code);


    err_code = nrf_drv_saadc_channel_init(1, &channel_config1);
    APP_ERROR_CHECK(err_code);
	
	err_code = nrf_drv_saadc_channel_init(2, &channel_config2);
    APP_ERROR_CHECK(err_code);
	
	err_code = nrf_drv_saadc_channel_init(3, &channel_config3);
    APP_ERROR_CHECK(err_code);
	
	err_code = nrf_drv_saadc_channel_init(4, &channel_config4);
    APP_ERROR_CHECK(err_code);
	
	
	err_code = nrf_drv_saadc_channel_init(5, &channel_config5);
    APP_ERROR_CHECK(err_code);
	
	
	err_code = nrf_drv_saadc_channel_init(6, &channel_config6);
    APP_ERROR_CHECK(err_code);
	
	
	err_code = nrf_drv_saadc_channel_init(7, &channel_config7);
    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);
}

int main(void)
{
    uint32_t err_code;
    bool     erase_bonds;

    //Initialize.
    APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, false);
    uart_init();

    buttons_leds_init(&erase_bonds);
    ble_stack_init();
    gap_params_init();
    services_init();
    advertising_init();
    conn_params_init();

    printf("\r\nUART Start!\r\n");
    err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
    APP_ERROR_CHECK(err_code);

	printf("SAADC HAL simple example.\r\n");
	
	saadc_init();
    saadc_sampling_event_init();
    saadc_sampling_event_enable();
	
	
    //Enter main loop.
    for (;;)
    {
        power_manage();
    }
}

This is the conversion result

ADC event number: 9
40
31
26
336
129
83
66
60

The voltage of these eight channels are the same about 0.6v

[Jørgen Holmefjord]

Are the pins connected to a source giving 0.6V? Are you testing this on the nRF52-DK (PCA10040 board)? Note that AIN3 are shared with GPIO P0.05, which is used for UART connection on the development kit.

[awneil]

Note that it's not necessary to have a separate channel config structure for each channel - you can have just one, and update the pin_p for each nrf_drv_saadc_channel_init() call.

Follow-up: https://devzone.nordicsemi.com/f/nordic-q-a/45263/saadc-multiple-channel-acquisition - on getting all the channels sampled "simultaneously"