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#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// Define the resistance value (8 ohms)
const float resistorResistance = 8.0;

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

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  delay(500);
  display.clearDisplay();

  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0, 00);
  // Display static text
  display.println("NIMH Batt discharger");
  display.display(); 
}

void loop() {
  
  // Data regarding battery B1:

  // read the input on analog pin 0:
  int sensorValue_B1 = analogRead(A0);
  
  // print out the value you read:
  Serial.println(sensorValue_B1);      // Print ADC value from A0 to serial monitor
  float voltage_B1 = sensorValue_B1 * (5.0 / 1023.0);      // Convert ADC value from A0 into measured voltage
  
  // Calculate current (I = V_R / R)
  float current_mA_B1 = voltage_B1 / resistorResistance * 1000;

  // Use sprintf() command to insert zero's in front of calculated/measured B1 value so that there always is 4 characters
  int calculatedNumber_B1 = current_mA_B1; // Make an int containing the calculated B1 current
  char formattedNumber_B1[4]; // Buffer to store the formatted number always with 4 characters
  sprintf(formattedNumber_B1, "%04d", calculatedNumber_B1);



  display.setCursor(0, 10);
  display.setTextColor(WHITE, BLACK);
  display.println("                     ");      // Erase line with black spaces, so it's ready to write a new line in white
  display.setTextColor(WHITE);
  display.setCursor(0, 10);
  display.print("B1 ");
  display.print(voltage_B1, 3);      // Write converted A0 ADC value to OLED with 3 decimals
  display.print("V ");
  display.print(formattedNumber_B1); // Write formattedNumber_B1 to OLED always with 4 characters
  display.println("mA");
  display.display(); 
  delay(250);             // delay in between reads for stability  
}