Hi,
I'm trying to read the battery voltage of a custom board from the VDDHDIV5 channel. I'm using FreeRTOS in my project. I would like to read trigger the ADC to read 5 samples(non-blocking) once every hour. I tried the below pseudo code to trigger the read but I noticed that only one reading is present in the buffer.
nrf_saadc_value_t raw_value[5] = {0};
void saadc_handler(nrf_drv_saadc_evt_t const * p_event)
{
if(p_event->type == NRF_DRV_SAADC_EVT_DONE)
{
raw_val = *(p_event->data.done.p_buffer);
test = (raw_val*10/1024);
//Notify saadc_thread
}
}
void saadc_init()
{
uint32_t err_code;
//SAADC peripheral configuration
nrf_drv_saadc_config_t m_saadc_config =
{
.interrupt_priority = APP_IRQ_PRIORITY_LOW,
.low_power_mode = false,
.oversample = NRF_SAADC_OVERSAMPLE_DISABLED,
.resolution = NRF_SAADC_RESOLUTION_10BIT
};
// Channel configuration
//Internal reference is 0.6V
nrf_saadc_channel_config_t m_channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_VDDHDIV5);
m_channel_config.acq_time = NRF_SAADC_ACQTIME_10US;
m_channel_config.gain = NRF_SAADC_GAIN1_6;
err_code = nrf_drv_saadc_init(&m_saadc_config, saadc_handler);
APP_ERROR_CHECK(err_code);
err_code = nrf_drv_saadc_channel_init(0, &m_channel_config);
APP_ERROR_CHECK(err_code);
}
void saadc_sample()
{
nrf_drv_saadc_buffer_convert(raw_value, 5);
for(uint8_t i=0; i<5; ++i)
nrf_drv_saadc_sample();
}
static void saadc_thread(void * arg)
{
// Call saadc_sample and wait for a notification. And then delay for 1 hour
}I tried two more things and noticed different output
- The SAADC example in the SDK. The code was running fine and the ADC values were correct.
- Call saadc_sample in the SAADC handler on NRF_DRV_SAADC_EVT_DONE. The ADC values were correct but this is not a desirable situation as I don't need the SAADC to constantly sample
- Change the size of raw_value to 1. The ADC value was wrong. I tried this with and without oversampling.
MCU - nRF52833-QDAAA0
SDK - nRF5 SDK 17.1.0
With FreeRTOS
