coffee_scales.ino

#include "./HX711.h"
#include <stdlib.h>     /* abs */
/********************************/
// include the library code
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 20, 4); // set the LCD address to 0x27 for a 16 chars and 2 line display
/*********************************************************/

HX711 scale;

int ssrPin = 11;
int ledPin = 10;
int buttonPin = 2;
unsigned long time;
long previousmillis = 0;
long interval = 300;
long startTime = 0;
bool started = false;
bool firstRun = true;
int reading;

void setup() {
  lcd.init();  //initialize the lcd
  lcd.backlight();  //open the backlight
  lcd.setCursor ( 0, 0 );            // go to the top left corner
  lcd.print("   Espresso Scale   "); // write this string on the top row
  lcd.setCursor ( 0, 2 );            // go to the top left corner
  lcd.print("Press button to brew"); // write this string on the top row
  Serial.begin(38400);
  Serial.println("Initializing the scale");
  pinMode(ssrPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP); //logic inversed as we use internal pullup to avoid needing resistor and hence many more cables
  preparescale();
}

void preparescale() {
  // parameter "gain" is ommited; the default value 128 is used by the library
  // HX711.DOUT  - pin #A1
  // HX711.PD_SCK - pin #A0
  scale.begin(A1, A0);
  scale.set_scale(-1573);

}

void coffeeloop() {
  if (firstRun == true) {
    startTime = millis();
    firstRun = false;
    Serial.println("first run");
    Serial.println(startTime);
  }
  // handle current time
  time = millis() - startTime;
  char timebuff[20];
  lcd.setCursor(0, 2);
  sprintf(timebuff, "        %lus          ", time / 1000);
  Serial.println(timebuff); // why do I need this to stop time freezing at 10s?
  lcd.print(timebuff);

  // handle weight
  float x = scale.get_units(5);
  x = abs(x);
  lcd.setCursor ( 0, 1 );            // go to the top left corner
  char buffer[20];
  char output[30];
  dtostrf(x, 2, 0, buffer);
  sprintf(output, "        %s%s        ", buffer, "g");
  lcd.print(output);

  // stop if target exceeded (allowance for overrun of pump after switching ssr
  if (x > 35.0) {
    digitalWrite(ssrPin, LOW);
    digitalWrite(ledPin, LOW);
    lcd.setCursor(0, 3);
    lcd.print("  Brewing stopped  ");
    exit(0);
  }
}

void loop() {
  reading = digitalRead(buttonPin);
  if (started == true) {
    coffeeloop();
  } else if (reading == LOW && started == false) {
    started = true;
    scale.tare();
    digitalWrite(ssrPin, HIGH);
    digitalWrite(ledPin, HIGH);

  }
}