Hello all,
I am having a problem to get SAADC to work with low power. I am using custom board with chip NRF52811, SDK 16.0.0.
I had turned on the SAADC_CONFIG_LP_MODE in the config file.
#ifndef SAADC_CONFIG_LP_MODE #define SAADC_CONFIG_LP_MODE 1 #endif
When using 1 channel, I get the current consumption of 35 uA for the whole circuit, which is nice for my application. But when add another channel, the current consumption now goes to 900 uA.
ret_code_t err_code;
nrf_drv_saadc_config_t saadc_config;
nrf_saadc_channel_config_t channel_config_1;
nrf_saadc_channel_config_t channel_config_2;
//Configure SAADC
saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT; //Set SAADC resolution to 12-bit. This will make the SAADC output values from 0 (when input voltage is 0V) to 2^12=2048 (when input voltage is 3.6V for channel gain setting of 1/6).
saadc_config.oversample = NRF_SAADC_OVERSAMPLE_DISABLED ; //Set oversample to disabled (will give unwanted output with scan mode).
saadc_config.interrupt_priority = APP_IRQ_PRIORITY_LOW; //Set SAADC interrupt to low priority.
//Initialize SAADC
err_code = nrf_drv_saadc_init(&saadc_config, ADC_CallBack); //Initialize the SAADC with configuration and callback function. The application must then implement the saadc_callback function, which will be called when SAADC interrupt is triggered
APP_ERROR_CHECK(err_code);
//Configure SAADC channel
channel_config_1.reference = NRF_SAADC_REFERENCE_INTERNAL; //Set internal reference of fixed 0.6 volts
channel_config_1.gain = NRF_SAADC_GAIN1; //Set input gain to 1/6. The maximum SAADC input voltage is then 0.6V/(1/6)=3.6V. The single ended input range is then 0V-3.6V
channel_config_1.acq_time = NRF_SAADC_ACQTIME_10US; //Set acquisition time. Set low acquisition time to enable maximum sampling frequency of 200kHz. Set high acquisition time to allow maximum source resistance up to 800 kohm, see the SAADC electrical specification in the PS.
channel_config_1.mode = NRF_SAADC_MODE_SINGLE_ENDED; //Set SAADC as single ended. This means it will only have the positive pin as input, and the negative pin is shorted to ground (0V) internally.
channel_config_1.pin_p = NRF_SAADC_INPUT_AIN3; //Select the input pin for the channel. AIN0 pin maps to physical pin P0.02.
channel_config_1.pin_n = NRF_SAADC_INPUT_DISABLED; //Since the SAADC is single ended, the negative pin is disabled. The negative pin is shorted to ground internally.
channel_config_1.resistor_p = NRF_SAADC_RESISTOR_DISABLED; //Disable pullup resistor on the input pin
channel_config_1.resistor_n = NRF_SAADC_RESISTOR_DISABLED;
channel_config_1.burst = NRF_SAADC_BURST_DISABLED;
err_code = nrf_drv_saadc_channel_init(3, &channel_config_1);
APP_ERROR_CHECK(err_code);
//Configure SAADC channel
channel_config_2.reference = NRF_SAADC_REFERENCE_INTERNAL; //Set internal reference of fixed 0.6 volts
channel_config_2.gain = NRF_SAADC_GAIN1; //Set input gain to 1/6. The maximum SAADC input voltage is then 0.6V/(1/6)=3.6V. The single ended input range is then 0V-3.6V
channel_config_2.acq_time = NRF_SAADC_ACQTIME_10US; //Set acquisition time. Set low acquisition time to enable maximum sampling frequency of 200kHz. Set high acquisition time to allow maximum source resistance up to 800 kohm, see the SAADC electrical specification in the PS.
channel_config_2.mode = NRF_SAADC_MODE_SINGLE_ENDED; //Set SAADC as single ended. This means it will only have the positive pin as input, and the negative pin is shorted to ground (0V) internally.
channel_config_2.pin_p = NRF_SAADC_INPUT_AIN1; //Select the input pin for the channel. AIN0 pin maps to physical pin P0.02.
channel_config_2.pin_n = NRF_SAADC_INPUT_DISABLED; //Since the SAADC is single ended, the negative pin is disabled. The negative pin is shorted to ground internally.
channel_config_2.resistor_p = NRF_SAADC_RESISTOR_DISABLED; //Disable pullup resistor on the input pin
channel_config_2.resistor_n = NRF_SAADC_RESISTOR_DISABLED; //Disable pulldown resistor on the input pin
channel_config_2.burst = NRF_SAADC_BURST_DISABLED;
err_code = nrf_drv_saadc_channel_init(1, &channel_config_2);
APP_ERROR_CHECK(err_code);
err_code = nrf_drv_saadc_buffer_convert(m_buffer[0], SAMPLES_IN_BUFFER); //Set SAADC buffer 1. The SAADC will start to write to this buffer
APP_ERROR_CHECK(err_code);
err_code = nrf_drv_saadc_buffer_convert(m_buffer[1], SAMPLES_IN_BUFFER); //Set SAADC buffer 2. The SAADC will write to this buffer when buffer 1 is full. This will give the applicaiton time to process data in buffer 1.
APP_ERROR_CHECK(err_code);
is_ADC_initialized = true;What I am doing wrong ?
Best regards,
