Studio XIAO nRF52840 (Sense) battery pins number

Products & Technology XIAO
#1

Am wondering what is the pin number of Studio XIAO nRF52840 (Sense) battery pins which are on the back, they are not mentioned in the pinout diagram

image
image702×372 67.7 KB

i have solder lipo battery to these pins and i want to monitor battery usage via code and want to send info to my android app so that i know how much battery is left so that can be recharged on time.

code

#define VBAT_PIN          (A7)

// 3.0V ADC range and 12-bit ADC resolution = 3000mV/4096
#define VBAT_MV_PER_LSB   (0.73242188F)

// 2M + 0.806M voltage divider on VBAT = (2M / (0.806M + 2M))
#define VBAT_DIVIDER      (0.71275837F)

// Compensation factor for the VBAT divider
#define VBAT_DIVIDER_COMP (1.403F)

int vbat_raw;
uint8_t vbat_per;
float vbat_mv;

void setup(void) {
  Serial.begin(115200);

  analogReference(AR_INTERNAL_3_0);
  analogReadResolution(12);  // Can be 8, 10, 12 or 14
  delay(1);
}

void loop(void) {
  vbat_raw = analogRead(VBAT_PIN);
  vbat_per = mvToPercent(vbat_raw * VBAT_MV_PER_LSB);

  // FIXME: Using C-style cast.  Use static_cast<float>(...)
  // instead  [readability/casting] [4]
  // Remove [readability/casting] ignore from Makefile
  vbat_mv = (float)vbat_raw * VBAT_MV_PER_LSB * VBAT_DIVIDER_COMP;

  Serial.print("ADC = ");
  Serial.print(vbat_raw * VBAT_MV_PER_LSB);
  Serial.print(" mV (");
  Serial.print(vbat_raw);
  Serial.print(") ");
  Serial.print("LIPO = ");
  Serial.print(vbat_mv);
  Serial.print(" mV (");
  Serial.print(vbat_per);
  Serial.println("%)");

  delay(4000);
}

uint8_t mvToPercent(float mvolts) {
  uint8_t battery_level;

  if (mvolts >= 3000) {
    battery_level = 100;
  } else if (mvolts > 2900) {
    battery_level = 100 - ((3000 - mvolts) * 58) / 100;
  } else if (mvolts > 2740) {
    battery_level = 42 - ((2900 - mvolts) * 24) / 160;
  } else if (mvolts > 2440) {
    battery_level = 18 - ((2740 - mvolts) * 12) / 300;
  } else if (mvolts > 2100) {
    battery_level = 6 - ((2440 - mvolts) * 6) / 340;
  } else {
    battery_level = 0;
  }

  return battery_level;
}

so what should be value of VBAT_PIN ?? as the back battery pins have no name mentioned on it.

  • am using seeed nr52840 standard arduino pacakge not Mbed OS
    thanks
#2

The following link will answer your questions
.
‘Getting Started | Seeed Studio Wiki’

Battery charging schematic in the section “Q3: What are the considerations when using XIAO nRF52840 (Sense) for battery charging?”

#3

hmmm ok i checked it however its big confusing not much info about monitoring there . however they mentioned : D14 pin so this mean in my sample code if i set VBAT_PIN to D14 i should get reading ?
so i tested by setting VBAT to D14 and connected battery it rear am still getting 0 .
is there any other working sample code someone have with proper instruction maybe so that can easily be replicated to monitor battery

thanks

#4

Try the code below.

//----------------------------------------------------------------------------------------------
//Board Library : Seeed nRF52 Borads 1.1.1
//Board Select  : Seeed nRF52 Borads / Seeed XIAO nRF52840 Sense
//----------------------------------------------------------------------------------------------
#include <Arduino.h>
#include <Adafruit_TinyUSB.h>   // for Serial.print()

//Arduino15\packages\Seeeduino\hardware\nrf52\1.1.4\variants\Seeed_XIAO_nRF52840_Sense\variant.cpp
#define PIN_VBAT        (32)  // D32 battery voltage
#define PIN_VBAT_ENABLE (14)  // D14 LOW:read anable
#define PIN_HICHG       (22)  // D22 charge current setting LOW:100mA HIGH:50mA
#define PIN_CHG         (23)  // D23 charge indicatore LOW:charge HIGH:no charge

void setup() 
{
  Serial.begin(115200);
  while(!Serial);
  
  pinMode(PIN_VBAT, INPUT);
  pinMode(PIN_VBAT_ENABLE, OUTPUT);
  pinMode(PIN_HICHG, OUTPUT);
  pinMode(PIN_CHG, INPUT);

  digitalWrite(PIN_VBAT_ENABLE, LOW); // VBAT read enable
  digitalWrite(PIN_HICHG, LOW);       // charge current 100mA
  
  // initialise ADC wireing_analog_nRF52.c:73
  analogReference(AR_DEFAULT);        // default 0.6V*6=3.6V  wireing_analog_nRF52.c:73
  analogReadResolution(12);           // wireing_analog_nRF52.c:39
 
}

void loop() 
{
  int vbatt = analogRead(PIN_VBAT);
  Serial.print(vbatt, HEX);
  Serial.print("    ");
  Serial.print(2.961 * 3.6 * vbatt / 4096);   // Resistance ratio 2.961, Vref = 3.6V 
  Serial.print("    ");
  Serial.println(digitalRead(PIN_CHG));       // 0:charge, 1:discharge 

  delay(1000);
}
1 Like
#5

ok great thanks :slight_smile: its working OK. Such nooobs screen shots related to hardware specific operation should be provided by seeed too. on their how to start pages