Reading Battery Level nrf52840

RE: Reading Battery Level nrf52840

John12 — Thu, 05 May 2022 11:13:04 GMT

Thanks for your kind reply. I got it :D

RE: Reading Battery Level nrf52840

Marcos Tadeo — Wed, 04 May 2022 16:31:40 GMT

Hi john12

in this line read and covert the analog input to bits , and pass the data to varaible "adc_val" i am using 10bits resolution

nrfx_saadc_sample_convert(0,&adc_val);

this is the equation to get the voltage value, multiplicate the adc_value * Vdd( The Vdd 3.3v), devide by 1024(10 bits resolution) * your deviser voltage for example if you have R1=800k and R2=2M

devide R2/R1 = 2M/800k = 2.5 this is the porpotion, you can see this https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/measuring-lithium-battery-voltage-with-nrf52

this line is wrong,

valueVoltaje = (adc_val * 4.2f / 1024)*0.91;

the power supply for micro nrf52 is 1.8v to 3.6v i am using 3.6v aprox, then your maximun voltage analog input is 3.3v

valueVoltaje = (adc_val * 3.6f / 1024)*2.5;

and this part

porcentaje = (valueVoltaje/3.6f)*100;

its for voltage battery percent

here I little tutorial about this example

https://youtu.be/HfuIPiBgTfg

sorry , my English is not good xd

but I hope to help you

RE: Reading Battery Level nrf52840

John12 — Wed, 04 May 2022 02:42:29 GMT

Hi Marcos,
I'm buiding this application on nRF52833 as well.
I started with this topic 1 days ago
So Can you explain for me this piece of code ? Thanh you very much

    while (1)
    {
      nrfx_saadc_sample_convert(0,&adc_val);
			
			valueVoltaje = (adc_val * 4.2f / 1024)*0.91;// 1.07  calculo del parametro a utilizar para captura de voltaje de la bateria
			porcentaje = (valueVoltaje/4.2f)*100;
	}

RE: Reading Battery Level nrf52840

Marcos Tadeo — Mon, 02 May 2022 15:13:57 GMT

oohh ok, nice!

thank you very much ketiljo

best reagrds

RE: Reading Battery Level nrf52840

ketiljo — Mon, 02 May 2022 12:02:08 GMT

You can only have VDD or the internal 0.6 V as a reference, there are no external references available, see https://infocenter.nordicsemi.com/topic/ps_nrf52840/saadc.html

If you want to measure the battery voltage, you need to measure single ended.

RE: Reading Battery Level nrf52840

Marcos Tadeo — Fri, 29 Apr 2022 15:03:21 GMT

Hi Ketiljo

thank you for to response

I have a question about external refence voltage, how can i do that?,

void saadc_init(void)
{
	ret_code_t err_code;
	nrf_saadc_channel_config_t channel_config = NRFX_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);
	
  
	
	err_code = nrf_drv_saadc_init(NULL, saadc_callback_handler);
	APP_ERROR_CHECK(err_code);
	
	err_code = nrfx_saadc_channel_init(0,&channel_config);
	APP_ERROR_CHECK(err_code);
	
}

my reference voltage now is 3.3 but I need to change to 1.8 in vdd , I want to do a test with 1.8v

is single ended or diferential with ?

NRFX_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN1);

nrf_saadc_channel_config_t channel_config = NRFX_SAADC_DEFAULT_CHANNEL_CONFIG_DIFFERENTIAL(NRF_SAADC_INPUT_VDD,NRF_SAADC_INPUT_AIN1);

thank you and regards

RE: Reading Battery Level nrf52840

ketiljo — Thu, 28 Apr 2022 07:35:13 GMT

Resistors this small will draw too much current. Take a look at this: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/measuring-lithium-battery-voltage-with-nrf52