SAADC inconsistent buffer channnel

[Sumbo]

Good Day,

i´m want to use saadc with 7 channels. I´m using the ADC Driver with an interupt handler. All 10ms the sampling starts per cpu. I use the configuration followed:

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 /* lokale Variablen */
    nrfx_saadc_config_t stADCCfg;
    nrf_saadc_channel_config_t stChCfg;

    /* generelle Konfiguration */
    nrfx_saadc_uninit();
    stADCCfg.resolution     = NRF_SAADC_RESOLUTION_12BIT;

    stADCCfg.oversample     = NRF_SAADC_OVERSAMPLE_2X;
    nrfx_saadc_init( &stADCCfg, HWADCEvent );

    /* Voreinstellungen alle Kanäle */

    stChCfg.acq_time    = NRF_SAADC_ACQTIME_20US;

    stChCfg.burst       = NRF_SAADC_BURST_ENABLED;
    stChCfg.gain        = NRF_SAADC_GAIN1_4;
    stChCfg.mode        = NRF_SAADC_MODE_SINGLE_ENDED;
    stChCfg.reference   = NRF_SAADC_REFERENCE_VDD4;
    stChCfg.resistor_n  = NRF_SAADC_RESISTOR_DISABLED;
    stChCfg.resistor_p  = NRF_SAADC_RESISTOR_DISABLED;
   
  
    /* PIR Sensor 1 (Sens1) */
    nrfx_saadc_channel_uninit(0);
    stChCfg.pin_p = NRF_SAADC_INPUT_AIN6;
    nrfx_saadc_channel_init( 0, &stChCfg );

    /* PIR Sensor 2 (Sens2) */
    nrfx_saadc_channel_uninit(1);
    stChCfg.pin_p = NRF_SAADC_INPUT_AIN7;
    nrfx_saadc_channel_init( 1, &stChCfg );

    /* PIR Sensor 3 (Sens3) */
    nrfx_saadc_channel_uninit(2);
    stChCfg.pin_p = NRF_SAADC_INPUT_AIN0;
    nrfx_saadc_channel_init( 2, &stChCfg );

    /* PIR Sensor 4 (Sens4) */
    nrfx_saadc_channel_uninit(3);
    stChCfg.pin_p = NRF_SAADC_INPUT_AIN1;
    nrfx_saadc_channel_init( 3, &stChCfg );

        /* Sensor variante detection (Sensor Variante) */
    nrfx_saadc_channel_uninit(4);
    stChCfg.pin_p = NRF_SAADC_INPUT_AIN5;
    nrfx_saadc_channel_init( 4, &stChCfg );

        /* Temperature sensor NTC (SensNTC) */
    nrfx_saadc_channel_uninit(5);
    stChCfg.pin_p = NRF_SAADC_INPUT_AIN4;
    nrfx_saadc_channel_init( 5, &stChCfg );

        /* Last variante detection (Last Variante) */
    nrfx_saadc_channel_uninit(6);
    stChCfg.pin_p = NRF_SAADC_INPUT_AIN2;
    nrfx_saadc_channel_init( 6, &stChCfg );

    /* buffering */

    nrfx_saadc_buffer_convert(m_buffer_pool[0], 7);
    nrfx_saadc_buffer_convert(m_buffer_pool[1], 7);
    nrfx_saadc_buffer_convert(m_buffer_pool[2], 7);
    nrfx_saadc_buffer_convert(m_buffer_pool[3], 7);
    nrfx_saadc_buffer_convert(m_buffer_pool[4], 7);
    nrfx_saadc_buffer_convert(m_buffer_pool[5], 7);
    nrfx_saadc_buffer_convert(m_buffer_pool[6], 7);

    /* calibration */
    nrfx_saadc_calibrate_offset();

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Periodically the sampling starts with:

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 nrfx_saadc_sample();

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If the conversation is finished, the interupt handler like followed starts...

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void HWADCEvent( nrfx_saadc_evt_t const * p_event )
{

    switch ( p_event->type )
    {
        case NRFX_SAADC_EVT_DONE:
            nrfx_saadc_buffer_convert(p_event->data.done.p_buffer,7);  

            val1   = p_event->data.done.p_buffer[0];
            val2   = p_event->data.done.p_buffer[1];
            val3   = p_event->data.done.p_buffer[2];
            val4   = p_event->data.done.p_buffer[3];
            val5 = p_event->data.done.p_buffer[4];
            val6        = p_event->data.done.p_buffer[5];
            val7   = p_event->data.done.p_buffer[6];
            break;
        case NRFX_SAADC_EVT_LIMIT:
            break;
        case NRFX_SAADC_EVT_CALIBRATEDONE:
            break;
        default:
            break;
           
    }

}

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If I starts the program, the values channels are  swapping in fiew minutes. For example val1 have got the value from channel 6, val2 frome channel 1 and so on.

Sometimes it runs 20 minutes good, then the channels are inconsistent. Sometimes it runs only 2minutes and the values are inconsistent. 

I don´t can find the mistake. My Buffer-Size is as long as the number of variables. What did I wrong?

I played with the interupt priority of the adc channels and with the aquitiontime without success. I spend a lot of time to find the mistake but i cant´t finde them. Can you help me?

[haakonsh]

It's a known issue. 

The workaround is to use at least two buffers(ping-pong) and connect the END event to the START task via PPI. 

You need to update the RESULT.PTR and RESULT.MAXCOUNT registers immediately after you've gotten a STARTED event (nrfx_saadc_buffer_convert). If the RESULT registers are not updated before the START task is triggered you will overwrite the previous buffer, therefore you will also need to make sure that you use large enough buffers. 

[Sumbo]

1. I don´t want to use PPI.

2.How I can update the RESULT.PTR and RESULT.MAXCOUNT if I use driver?

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3.In the Interupt handler I use nrfx_saadc_Buffer_convert immediatley the conversation is finished and before the next conversation starts.

[Sumbo]

Ok, I called the sampling twice. First with an interupt event. Secondly all 10m