Why Battery level is always 100?

Question

static void adc_init(void)

{

/* Enable interrupt on ADC sample ready event*/		

NRF_ADC->INTENSET = ADC_INTENSET_END_Msk;   

sd_nvic_SetPriority(ADC_IRQn, NRF_APP_PRIORITY_LOW);  

sd_nvic_EnableIRQ(ADC_IRQn);

NRF_ADC->CONFIG	= (ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos) 
		| (ADC_CONFIG_PSEL_Disabled << ADC_CONFIG_PSEL_Pos)					
		| (ADC_CONFIG_REFSEL_SupplyOneThirdPrescaling << ADC_CONFIG_REFSEL_Pos)							
		| (ADC_CONFIG_INPSEL_SupplyOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) 
		| (ADC_CONFIG_RES_8bit << ADC_CONFIG_RES_Pos);									

/* Enable ADC*/
NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Enabled;

}

void ADC_IRQHandler(void)

{

uint8_t adc_result;
	
    NRF_ADC->EVENTS_END = 0;	

ADC_Value = (NRF_ADC->RESULT)/255*100;

    NRF_ADC->TASKS_STOP = 1;

sd_clock_hfclk_release();

}

The result of this source is always 100.

The amount of the battery is falling but 100.

What is the problem?

I have connected the battery to the VTG and GND.

What part did wrong?

MANGO · Accepted Answer

Hi, I think this depends on what battery you are using. 
 If you see app_util.h, you'll see this block reference. 
 /** @brief Function for converting the input voltage (in milli volts) into percentage of 3.0 Volts.

*
* @details The calculation is based on a linearized version of the battery's discharge
* curve. 3.0V returns 100% battery level. The limit for power failure is 2.1V and
* is considered to be the lower boundary.
*
* The discharge curve for CR2032 is non-linear. In this model it is split into
* 4 linear sections:
* - Section 1: 3.0V - 2.9V = 100% - 42% (58% drop on 100 mV)
* - Section 2: 2.9V - 2.74V = 42% - 18% (24% drop on 160 mV)
* - Section 3: 2.74V - 2.44V = 18% - 6% (12% drop on 300 mV)
* - Section 4: 2.44V - 2.1V = 6% - 0% (6% drop on 340 mV)
*
* These numbers are by no means accurate. Temperature and
* load in the actual application is not accounted for!
*
* @param[in] mvolts The voltage in mV
*
* @return Battery level in percent.
*/
 
 As you see, the function 
 static __INLINE uint8_t battery_level_in_percent(const uint16_t mvolts)
 
 returns results following the reference. The CR2032 is a coin cell. 
 So if you use other batteries, the result would be quite different. 
 In my case, I use a custom board attaching two AA batteries in series. 
 So I also get 100% most of the time, unless the battery level has decreased dramatically. 
 So in short, 
 the program doesn't have problem. This depends on what battery you use. 
 If you want to see the percentage drop from any Nordic App, 
 how about connecting your kit or board to the power supply and switch the voltage level? 
 Then you'll see the level dropping. 
 -Regards, Mango922

Why Battery level is always 100?

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