SparkFun Forums

[baqjosue]

Hi, I have the following setup:

1. SparkFun Artemis Thing Plus
https://www.sparkfun.com/products/15574
1.1 3.7V 522332 400mAh Lipo battery Rechargeable Lithium Polymer ion Battery Pack with PH2.0mm JST Connector
https://www.amazon.com/Battery-Recharge ... B07BTWMM8H
2. SparkFun Photodetector Breakout - MAX30101 (Qwiic)
https://www.sparkfun.com/products/16474
3. SparkFun Micro OLED Breakout (Qwiic)
https://www.sparkfun.com/products/22495

The Artemis Thing Plus is the main board, the Lipo battery is connected to the JST connector, and it works perfectly. The MAX30101 is a light sensor, and the Micro OLED Breakout is the display. All parts work beautifully together, BUT now I want to add to my code to read the battery level. The battery works perfectly for ours, and it is charged via USB-C.

I want to see the battery level percentage displayed on my OLED.

This is my current code:

Code: Select all

#include <SFE_MicroOLED.h>
#include <Wire.h>

#include "MAX30105.h"

#define PIN_RESET 9
#define DC_JUMPER 1

MAX30105 particleSensor;
MicroOLED oled(PIN_RESET, DC_JUMPER);

long unblockedValue;  // Average IR at power up

String multiplyChar(char c, int n) {
  String result = "";
  for (int i = 0; i < n; i++) {
    result += c;
  }
  return result;
}

void displayMeasurement(int rLevel) {
  oled.clear(PAGE);
  oled.setCursor(0, 0);

  int calibratedReading = f(rLevel);
  int centerPadding = 4 - String(calibratedReading).length();
  String paddingText = multiplyChar(' ', centerPadding);

  if (rLevel == 0) {
    oled.setFontType(1);
    oled.print("Please load   sample!");
    oled.display();
    return;
  }

  oled.setFontType(3);
  oled.print(paddingText);
  oled.print(calibratedReading);

  Serial.println("real:" + String(rLevel));
  Serial.println("agtron:" + String(calibratedReading));
  Serial.println("===========================");

  oled.display();
}

int f(int x) {
  int intersectionPoint = 117;
  float deviation = 0.165;

  return round(x - (intersectionPoint - x) * deviation);
}

void setup() {
  Serial.begin(9600);

  Wire.begin();
  oled.begin();      // Initialize the OLED
  oled.clear(ALL);   // Clear the display's internal memory
  oled.clear(PAGE);  // Clear the buffer.

  delay(100);  // Delay 100 ms
  oled.setFontType(3);

  // Initialize sensor
  if (particleSensor.begin(Wire, I2C_SPEED_FAST) == false)  // Use default I2C port, 400kHz speed
  {
    Serial.println("MAX30105 was not found. Please check wiring/power. ");
    while (1)
      ;
  }

  // The variable below calibrates the LED output on your hardware.
  byte ledBrightness = 135;

  byte sampleAverage = 4;  // Options: 1, 2, 4, 8, 16, --32--
  byte ledMode = 2;        // Options: 1 = Red only, --2 = Red + IR--, 3 = Red + IR + Green
  int sampleRate = 50;     // Options: 50, 100, 200, 400, 800, 1000, 1600, --3200--
  int pulseWidth = 411;    // Options: 69, 118, 215, --411--
  int adcRange = 16384;    // Options: 2048, --4096--, 8192, 16384

  particleSensor.setup(ledBrightness, sampleAverage, ledMode, sampleRate, pulseWidth, adcRange);  // Configure sensor with these settings

  particleSensor.setPulseAmplitudeRed(0);
  particleSensor.setPulseAmplitudeGreen(0);

  particleSensor.disableSlots();
  particleSensor.enableSlot(2, 0x02);  // Enable only SLOT_IR_LED = 0x02

  // Update to ignore readings under 30.000
  unblockedValue = 30000;
}

void loop() {
  int rLevel = particleSensor.getIR();
  long currentDelta = rLevel - unblockedValue;

  if (currentDelta > (long)100) {
    displayMeasurement(rLevel / 1000);
  } else {
    displayMeasurement(0);
  }
  delay(100);
}

Please, anything would help. I've read about this, but I'm unsure how to proceed. If it helps, forget about what the light sensor does. I want to be able to display the battery level percentage.

[paulvha]

you will need to connect the VBAT pin to one of the ADC pins with a voltage divider. The ADC can only handle up to 2V reference. So make a voltage divider with 2 x 100K resistors and take the middle point to the ADC pin. Take the result you read with analogRead() and multiply by 2: ((analogRead(PIN) * 2 ) / 1023) * 2 = Battery Voltage. You can then add that to your OLED output.

[baqjosue]

Hi Paul - Thanks for the reply. Would you happen to know where the ADC pins are located in the Artemis thing plus? Thank you.

Josue

[paulvha]

It says on the board A0 to A5..

[baqjosue]

Hi Paul,
Thank you for your advice, I'm having a problem because my code is not reading any changes from the battery; I would like to check something with you first.

I connected the VBAT pin to the ADC A0 pin with a voltage divider , 2 x 100K resistors.
Then, I took the middle point to A0 and the end to the GND pin.
So it looks like:
1. VBAT
2. Middle point - A0
3. GND

Is that correct? Please let me know what you think.

Josue

[paulvha]

that is what I would do.
What results do you get?
what sketch are you using ?

[baqjosue]

All I get on my display is "Bat: 0%" and it doesn't move from that.
Here is my code:

#include <SFE_MicroOLED.h>
#include <Wire.h>
#include "MAX30105.h"

#define PIN_RESET 9
#define DC_JUMPER 1

MAX30105 particleSensor;
MicroOLED oled(PIN_RESET, DC_JUMPER);

long unblockedValue; // Average IR at power up

// Battery reading setup
const int BATTERY_PIN = A0; // ADC pin connected to battery voltage
const float FULL_BATTERY_VOLTAGE = 4.2; // Full charge voltage
const float EMPTY_BATTERY_VOLTAGE = 2.75; // Cut-off voltage
const float MAX_ADC_READING = 1023.0;
const float ADC_REFERENCE_VOLTAGE = 3.3; // Assuming the reference voltage is 3.3V

String multiplyChar(char c, int n) {
String result = "";
for (int i = 0; i < n; i++) {
result += c;
}
return result;
}

float readBatteryVoltage() {
float adcValue = analogRead(BATTERY_PIN);
float batteryVoltage = (adcValue / MAX_ADC_READING) * ADC_REFERENCE_VOLTAGE * 2.0; // Adjust for voltage divider
return batteryVoltage;
}

int mapBatteryToPercentage(float voltage) {
voltage = constrain(voltage, EMPTY_BATTERY_VOLTAGE, FULL_BATTERY_VOLTAGE);
return (int)((voltage - EMPTY_BATTERY_VOLTAGE) / (FULL_BATTERY_VOLTAGE - EMPTY_BATTERY_VOLTAGE) * 100);
}

void displayBatteryPercentage(int percentage) {
oled.setFontType(0);
oled.print("Bat: ");
oled.print(percentage);
oled.print("%");
}

void displayMeasurement(int rLevel) {
oled.clear(PAGE);
oled.setCursor(0, 0);

if (rLevel == 0) {
oled.setFontType(1);
oled.print("Load sample!");

float batteryVoltage = readBatteryVoltage();
int batteryPercentage = mapBatteryToPercentage(batteryVoltage);
displayBatteryPercentage(batteryPercentage);

oled.display();
return;
}

int calibratedReading = f(rLevel);
int centerPadding = 4 - String(calibratedReading).length();
String paddingText = multiplyChar(' ', centerPadding);

oled.setFontType(3);
oled.print(paddingText);
oled.print(calibratedReading);

Serial.println("real:" + String(rLevel));
Serial.println("agtron:" + String(calibratedReading));
Serial.println("===========================");

oled.display();
}

int f(int x) {
int intersectionPoint = 117;
float deviation = 0.165;

return round(x - (intersectionPoint - x) * deviation);
}

void setup() {
Serial.begin(9600);

Wire.begin();
oled.begin(); // Initialize the OLED
oled.clear(ALL); // Clear the display's internal memory
oled.clear(PAGE); // Clear the buffer.

delay(100); // Delay 100 ms
oled.setFontType(3);

// Initialize sensor
if (particleSensor.begin(Wire, I2C_SPEED_FAST) == false) // Use default I2C port, 400kHz speed
{
Serial.println("MAX30105 was not found. Please check wiring/power. ");
while (1)
;
}

// The variable below calibrates the LED output on your hardware.
byte ledBrightness = 135;

byte sampleAverage = 4; // Options: 1, 2, 4, 8, 16, --32--
byte ledMode = 2; // Options: 1 = Red only, --2 = Red + IR--, 3 = Red + IR + Green
int sampleRate = 50; // Options: 50, 100, 200, 400, 800, 1000, 1600, --3200--
int pulseWidth = 411; // Options: 69, 118, 215, --411--
int adcRange = 16384; // Options: 2048, --4096--, 8192, 16384

particleSensor.setup(ledBrightness, sampleAverage, ledMode, sampleRate, pulseWidth, adcRange); // Configure sensor with these settings

particleSensor.setPulseAmplitudeRed(0);
particleSensor.setPulseAmplitudeGreen(0);

particleSensor.disableSlots();
particleSensor.enableSlot(2, 0x02); // Enable only SLOT_IR_LED = 0x02

// Update to ignore readings under 30.000
unblockedValue = 30000;

pinMode(BATTERY_PIN, INPUT);
}

void loop() {
int rLevel = particleSensor.getIR();
long currentDelta = rLevel - unblockedValue;

if (currentDelta > (long)100) {
displayMeasurement(rLevel / 1000);
} else {
displayMeasurement(0);
}
delay(100);
}

[paulvha]

just created a simple sketch (attached). Parallel to the 100K resistor between GND and central point I add a 2.2uF capacitor. (see top of sketch) Also I adjusted your reference voltage. This worked.

[baqjosue]

Paul,

I adjusted my setup to it will be easier to make the battery percentage reading easier. I am currently just using:

1. SparkFun Artemis Thing Plus
https://www.sparkfun.com/products/15574
2. 3.7V 522332 400mAh Lipo battery Rechargeable Lithium Polymer ion Battery Pack with PH2.0mm JST Connector
https://www.amazon.com/Battery-Recharge ... B07BTWMM8H
3. SparkFun Micro OLED Breakout (Qwiic)
https://www.sparkfun.com/products/22495

The Artemis Thing Plus is the main board, the Lipo battery is connected to the JST connector. I also followed you recommendations and I connected the VBAT pin to the ADC A0 pin with a voltage divider , 2 x 100K resistors. Then, I took the middle point to A0 and the end to the GND pin. Finally, parallel to the 100K resistor between GND and central point I added a 1uF capacitor.

So i created a new simpler script, but the voltage comes as 0.00. Could you please take a look at my code?
Also the main purpose of this is to check the battery percentage.

[paulvha]

did my example work ? If not what results do you get?

[baqjosue]

Paul, yes I followed your example, but I am just getting "0.00" reading.
Please check the attached code

[paulvha]

I don't see a direct problem in your example. However, if my example did not work unmodified you have a different problem. use my example and Instead of connecting to VBAT, connect the voltage divider to 3v3. If that does not work include some pictures.