AMMETER

#include <Wire.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_GFX.h>
#include <Adafruit_INA219.h>
#include <Fonts/FreeMono9pt7b.h>
#include <SPI.h>
#include <SD.h>
#define RECBUTTON 0

File myFile;
unsigned long timestamp;
int currentState;
int rec = 0;

Adafruit_INA219 ina219;

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32
#define OLED_RESET     -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

void setup() {
  delay(500); // calm down pause
  Serial.begin(115200);
  while (!Serial) {
    ;
  }
  pinMode(RECBUTTON, INPUT_PULLUP);
  if (!SD.begin(15)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);

  if (! ina219.begin()) {
    Serial.println("INA219 failed");
    while (1) {
      delay(10);
    }
  }
}


void loop() {
  currentState = digitalRead(RECBUTTON);

  if (currentState == LOW && rec == 1) {
    rec = 0;
    Serial.println("recording off");
    myFile.close();
  } else if (currentState == LOW && rec == 0) {
    rec = 1;
    Serial.println("recording on");
    myFile = SD.open("ammeter.txt", FILE_WRITE);
    myFile.println("ms;W;A;busvoltage;shuntvoltage;loadvoltage");
  }

  float shuntvoltage = 0;
  float busvoltage = 0;
  float current_mA = 0;
  float loadvoltage = 0;
  float power_mW = 0;

  shuntvoltage = ina219.getShuntVoltage_mV();
  busvoltage = ina219.getBusVoltage_V();
  current_mA = ina219.getCurrent_mA();
  power_mW = ina219.getPower_mW();
  loadvoltage = busvoltage + (shuntvoltage / 1000);

  delay(200);  // decrease if you want to increase number of recordings per second but display may flicker

  display.clearDisplay();
  display.setFont(&FreeMono9pt7b);
  display.setTextColor(WHITE);
  display.setCursor(0, 10);
  display.print("mA:"); display.print(current_mA);
  display.setCursor(0, 23);
  display.print("mW:"); display.print(power_mW);
  display.setFont(NULL);
  display.setTextSize(1);
  display.setCursor(0, 25);

  if (busvoltage < 0) busvoltage = 0;
  if (shuntvoltage < 0) shuntvoltage = 0;
  if (loadvoltage < 0) loadvoltage = 0;

  display.print("VB:"); display.print(busvoltage);
  display.print(" S:"); display.print(shuntvoltage);
  display.print(" L:"); display.print(loadvoltage);

  display.setCursor(100, 0);
  if (rec == 1) {
    display.print("[R]");
  }

  display.display();
  if (rec == 1) {
    myFile.print(millis());
    myFile.print(";");
    myFile.print(power_mW);
    myFile.print(";");
    myFile.print(current_mA * -1);
    myFile.print(";");
    myFile.print(busvoltage);
    myFile.print(";");
    myFile.print(shuntvoltage);
    myFile.print(";");
    myFile.println(loadvoltage);
  }
}