nRF24LE1 Supply voltage measurement

[tass]

Hi, i try to understand how to use mode for supply voltage measurement. But i have a problem and i get always 1.225 volt

   hal_adc_set_input_channel(HAL_INP_VDD2_3);
  hal_adc_set_reference(HAL_ADC_REF_INT);
  hal_adc_set_input_mode(HAL_ADC_SINGLE);
  hal_adc_set_conversion_mode(HAL_ADC_SINGLE_STEP);
  hal_adc_set_resolution(HAL_ADC_RES_8BIT);
  hal_adc_set_data_just(HAL_ADC_JUST_RIGHT);
		
		while (1)	
		{	
					hal_adc_start();                                // Start the ADC
    while( hal_adc_busy() )                         // Wait for the ADC to finish a conversion
    {
		}
		adc_mesurment=hal_adc_read_LSB();
		
		answer=adc_mesurment;
		voltage = 312.32 / answer; // Calculate  312.32 = 1.22 * 256 
		sprintf(uarttxbuffer,"voltage is %.3f volt\r\n",voltage);

I connect nrf with 3volt, 3,3volt, 4volt, but always i get 1.225 volt. Thanks...

[Hung Bui]

Hi Tass,

As mentioned in the ADC section in the nRF24LE1 spec, the ADC when in single ended mode measures voltage from 0V to VRef. So if you are using input which has voltage >VRef you will get all 0xFF.

You can try to use HAL_INP_VDD1_3 instead.

And note that you should not feed anything more than 3.6V to the chip.

[tass]

Special thanks Bui!!!!