RE: ADC sampling while the radio is transmitting

ovrebekk — Tue, 29 Dec 2020 16:07:16 GMT

Hi Ken

That is great news, I will close the case then 🙂

Best regards
Torbjørn

RE: ADC sampling while the radio is transmitting

Kenneth — Tue, 22 Dec 2020 21:56:08 GMT

Hi,

I initialized my SAADC wrong. I checked it again when you mentioned it and fixed it. It's working now.

Thank you for the suggestions.

Regards,

Ken

RE: ADC sampling while the radio is transmitting

ovrebekk — Tue, 22 Dec 2020 13:00:24 GMT

I can't see anywhere in your code snippets how you set up the ADC DMA buffers, and if you start the ADC anywhere (through the START task).

Are you doing this somewhere else, or is this not included?

Best regards
Torbjørn

RE: ADC sampling while the radio is transmitting

Kenneth — Mon, 21 Dec 2020 23:03:39 GMT

So this is how I set up PPI

static void ppi_init(void)
{
    uint32_t err_code = NRF_SUCCESS;


    err_code = nrf_drv_ppi_init();
    APP_ERROR_CHECK(err_code);

    /* Configure 1st available PPI channel to stop TIMER0 counter on TIMER1 COMPARE[0] match,
     * which is every even number of seconds.
     */
    err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel1);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_ppi_channel_assign(m_ppi_channel1,
                                          (uint32_t)&NRF_RADIO->EVENTS_TXREADY,
                                          (uint32_t)&NRF_SAADC->TASKS_START);
    APP_ERROR_CHECK(err_code);

    /* Configure 2nd available PPI channel to start TIMER0 counter at TIMER2 COMPARE[0] match,
     * which is every odd number of seconds.
     */
    err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel2);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_ppi_channel_assign(m_ppi_channel2,
                                          (uint32_t)&NRF_RADIO->EVENTS_TXREADY,
                                          (uint32_t)&NRF_SAADC->TASKS_SAMPLE);
    APP_ERROR_CHECK(err_code);

    // Enable both configured PPI channels
    err_code = nrf_drv_ppi_channel_enable(m_ppi_channel1);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_ppi_channel_enable(m_ppi_channel2);
    APP_ERROR_CHECK(err_code);
}

SAADC init

void Adc14bitPolledInitialise(void)
{
    uint32_t timeout = 10;  
    //Setup C
    nrf_saadc_channel_config_t myConfig =
    {
        .resistor_p = NRF_SAADC_RESISTOR_DISABLED,
        .resistor_n = NRF_SAADC_RESISTOR_DISABLED,
        .gain       = NRF_SAADC_GAIN1_6,
        .reference  = NRF_SAADC_REFERENCE_INTERNAL,
        .acq_time   = NRF_SAADC_ACQTIME_3US,
        .mode       = NRF_SAADC_MODE_SINGLE_ENDED,
        .burst      = NRF_SAADC_BURST_DISABLED,
        .pin_p      = NRF_SAADC_INPUT_VDD,
        .pin_n      = NRF_SAADC_INPUT_DISABLED
    };

    nrf_saadc_resolution_set((nrf_saadc_resolution_t) NRF_SAADC_RESOLUTION_14BIT);   // 2 is 12-bit
    nrf_saadc_oversample_set((nrf_saadc_oversample_t) 0);   // 0 no oversampling
    nrf_saadc_int_disable(NRF_SAADC_INT_ALL);
    nrf_saadc_event_clear(NRF_SAADC_EVENT_END);
    nrf_saadc_event_clear(NRF_SAADC_EVENT_STARTED);
    nrf_saadc_enable();

    NRF_SAADC->CH[1].CONFIG =
              ((myConfig.resistor_p << SAADC_CH_CONFIG_RESP_Pos)   & SAADC_CH_CONFIG_RESP_Msk)
            | ((myConfig.resistor_n << SAADC_CH_CONFIG_RESN_Pos)   & SAADC_CH_CONFIG_RESN_Msk)
            | ((myConfig.gain       << SAADC_CH_CONFIG_GAIN_Pos)   & SAADC_CH_CONFIG_GAIN_Msk)
            | ((myConfig.reference  << SAADC_CH_CONFIG_REFSEL_Pos) & SAADC_CH_CONFIG_REFSEL_Msk)
            | ((myConfig.acq_time   << SAADC_CH_CONFIG_TACQ_Pos)   & SAADC_CH_CONFIG_TACQ_Msk)
            | ((myConfig.mode       << SAADC_CH_CONFIG_MODE_Pos)   & SAADC_CH_CONFIG_MODE_Msk)
            | ((myConfig.burst      << SAADC_CH_CONFIG_BURST_Pos)  & SAADC_CH_CONFIG_BURST_Msk);

    NRF_SAADC->CH[1].PSELN = myConfig.pin_n;
    NRF_SAADC->CH[1].PSELP = myConfig.pin_p;

}

and in main, I just initiate both, and read the buffer if the address for saadc indicate finished.

log_init();
lfclk_config();
timers_init();
Adc14bitPolledInitialise();
power_management_init();
ble_stack_init();
gap_params_init();
gatt_init();
peer_manager_init();
services_init();
sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);
sd_power_mode_set(NRF_POWER_MODE_LOWPWR);
advertising_init();
conn_params_init();

ppi_init();

advertising_start(false);
// main loop.
for (;;)
{

    if( NRF_SAADC->EVENTS_DONE )
    {
        NRF_LOG_INFO("radio RX");
        stopAnalogSample(&vbat);
        advertisingUpdateMfgData();
    }

    idle_state_handle(); 
}

it just never get to the stopAnalogSample() function.

Am I doing something wrong here?

RE: ADC sampling while the radio is transmitting

ovrebekk — Fri, 18 Dec 2020 14:21:51 GMT

Hi Kenneth

It is possible to use the PPI controller to connect one of the radio events to the ADC SAMPLE task, so that the ADC sampling will be synchronized to the operation of the radio.

An overview of all the events in the radio can be found here.

Possible events of interest are the TXREADY or RXREADY events, which occur once the radio is started in TX or RX mode respectively.
You could also use the END event, which is triggered when a packet is successfully sentor received.

Best regards
Torbjørn