Hi Al
I'm implementing multiple channel ADC with PPI
sampling multiple ADC channels with PPI, adc event triggered adc_event_handler as many times as channels (instead of just once after completion of entire buffer)
I've used the RTC
uint32_t timer_compare_event_addr = (uint32_t)&NRF_RTC1->EVENTS_COMPARE[1];
uint32_t adc_sample_event_addr = nrf_drv_adc_start_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, adc_sample_event_addr);
APP_ERROR_CHECK(err_code);
To my understanding the size of adc buffer to be filled before triggering the event is defined so : (by ADC_BUFFER_SIZE)
APP_ERROR_CHECK(nrf_drv_adc_buffer_convert(adc_buffer,ADC_BUFFER_SIZE));
After starting the RTC with one channel everything is working fine
but if I use 2 channels (and say ADC_BUFFER_SIZE=8 element buffer), I get the event twice, the first after the first 4 and the second after the next 4.
If I use 3 channels (and say 9 element buffer ) I get the adc_ppi event 3 times (3,6,9)
I don't understand why this happens and would appreciate any insights!
Thanks a lot
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this is how I define the channels :
static nrf_drv_adc_channel_t m_channel_0_config = NRF_DRV_ADC_DEFAULT_CHANNEL(ADC_CONFIG_PSEL_AnalogInput6);
static nrf_drv_adc_channel_t m_channel_1_config = NRF_DRV_ADC_DEFAULT_CHANNEL(ADC_CONFIG_PSEL_AnalogInput7);
static nrf_drv_adc_channel_t m_channel_2_config = NRF_DRV_ADC_DEFAULT_CHANNEL(ADC_CONFIG_PSEL_AnalogInput0);
m_channel_0_config.config.config.input = NRF_ADC_CONFIG_SCALING_INPUT_ONE_THIRD;
m_channel_1_config.config.config.input = NRF_ADC_CONFIG_SCALING_INPUT_ONE_THIRD;
m_channel_2_config.config.config.input = NRF_ADC_CONFIG_SCALING_INPUT_ONE_THIRD;
nrf_drv_adc_channel_enable(&m_channel_0_config);
nrf_drv_adc_channel_enable(&m_channel_1_config);
nrf_drv_adc_channel_enable(&m_channel_2_config);
