How to cancel the last button pressed?

Using Arduino Programming Questions
1

Hello, I wrote a code for 8 buttons. Every time you press a button it will add up a value which is specified to a button. Now I want to program one of the button such that, it will cancel the last button pressed/cancel the last transaction made. The project is similar to a deposit machine. I tried if, else if but didn't work. What should I do? I have attached my code below.

//This is a code for buttons

#include <SPI.h>
int b1 = 5;
int b2 = 6;
int b3 = 9;
int b4 = 10;
int b5 = 11;
int b6 = 12;
int b7 = 13;
int b8 = A0;

int button1State = 0;
int button2State = 0;
int button3State = 0;
int button4State = 0;
int button5State = 0;
int button6State = 0;
int button7State = 0;
int button8State = 0;

double coin = 0.1;
double half = 0.5;
int one = 1;
int five = 5;
int ten = 10;
int twenty = 20
int confirm = 0;
int del = 0;

double total1 = 0.0;
double total2 = 0.0;
double total3 = 0.0;
double total4 = 0.0;
double total5 = 0.0;
double total6 = 0.0;
double total = 0.0;
double ftot = 0.0;

const int buzzer = A1;

void setup()
{
  pinMode(b1, INPUT);
  pinMode(b2, INPUT);
  pinMode(b3, INPUT);
  pinMode(b4, INPUT);
  pinMode(b5, INPUT);
  pinMode(b6, INPUT);
  pinMode(b7, INPUT);
  pinMode(b8, INPUT);
  pinMode(buzzer, OUTPUT);
  Serial.begin(9600);
}

void loop()
{
  // read the state of the pushbutton value
  button1State = digitalRead(b1);
  button2State = digitalRead(b2);
  button3State = digitalRead(b3);
  button4State = digitalRead(b4);
  button5State = digitalRead(b5);
  button6State = digitalRead(b6);
  button7State = digitalRead(b7);
  button8State = digitalRead(b8);
  // check if pushbutton is pressed.  if it is, the
  // button1State is HIGH
  if (button1State == HIGH)
  {
    total1 = total1 + one;
    Serial.print("Pay  ");
    Serial.print("1");
    Serial.println("?");
    total = total1+total2+total3+total4+total5+total6;
    Serial.print("Total = ");
    Serial.println(total);
    ftot = ftot + total;
    tone(buzzer, 1000);
    delay(500);
    noTone(buzzer);
    delay(500);
  }
  else
  {
    digitalWrite(buzzer,LOW);
  }
  delay(10); // Delay a little bit to improve simulation performance

  if (button2State == HIGH)
  {
    total2 = total2 + five;
    Serial.print("Pay ");
    Serial.print("5");
    Serial.println("?");
    total = total1+total2+total3+total4+total5+total6;
    Serial.print("Total = ");
    Serial.println(total);
    ftot = ftot + total;
    tone(buzzer, 1000);
    delay(500);
    noTone(buzzer);
    delay(500);
  }
  else
  {
    digitalWrite(buzzer,LOW);
  }
  delay(10); // Delay a little bit to improve simulation performance

  if (button3State == HIGH)
  {
    total3 = total3 + ten;
    Serial.print("Pay  ");
    Serial.print("10");
    Serial.println("?");
    total = total1+total2+total3+total4+total5+total6;
    Serial.print("Total = ");
    Serial.println(total);
    ftot = ftot + total;
    tone(buzzer, 1000);
    delay(500);
    noTone(buzzer);
    delay(500);
  }
  else
  {
    digitalWrite(buzzer,LOW);
  }
  delay(10); // Delay a little bit to improve simulation performance

  if (button4State == HIGH)
  {
    total4 = total4 + twenty;
    Serial.print("Pay ");
    Serial.print("20");
    Serial.println("?");
    total = total1+total2+total3+total4+total5+total6;
    Serial.print("Total = ");
    Serial.println(total);
    ftot = ftot + total;
    tone(buzzer, 1000);
    delay(500);
    noTone(buzzer);
    delay(500);
  }
  else
  {
    digitalWrite(buzzer,LOW);
  }
  delay(10); // Delay a little bit to improve simulation performance

  if (button5State == HIGH)
  {
    total5 = total5 + coin;
    Serial.print("Pay  ");
    Serial.print("0.1");
    Serial.println("?");
    total = total1+total2+total3+total4+total5+total6;
    Serial.print("Total = ");
    Serial.println(total);
    ftot = ftot + total;
    tone(buzzer, 1000);
    delay(500);
    noTone(buzzer);
    delay(500);
  }
  else
  {
    digitalWrite(buzzer,LOW);
  }
  delay(10); // Delay a little bit to improve simulation performance

  if (button6State == HIGH)
  {
    total6 = total6 + half;
    Serial.print("Pay ");
    Serial.print("0.5");
    Serial.println("?");
    total = total1+total2+total3+total4+total5+total6;
    Serial.print("Total = ");
    Serial.println(total);
    ftot = ftot + total;
    tone(buzzer, 1000);
    delay(500);
    noTone(buzzer);
    delay(500);
  }
  else
  {
    digitalWrite(buzzer,LOW);
  }
  delay(10); // Delay a little bit to improve simulation performance

**if (button7State == HIGH && total1>0)**
**  {**
**    total1 = total1 - one;**
**    total = total1 + total2 + total3 + total4+ total5+total6;**
**    Serial.println("Amount deleted.");**
**    Serial.println(total);**
**    tone(buzzer, 1000);**
**    delay(500);**
**    noTone(buzzer);**
**    delay(500);**
**  }**
** **
**  else if (button7State == HIGH && total2>0)**
**  {**
**    total2 = total2 - five;**
**    total = total1 + total2 + total3 + total4+ total5+total6;**
**    Serial.println("Amount deleted.");**
**    Serial.println(total);**
**    tone(buzzer, 1000);**
**    delay(500);**
**    noTone(buzzer);**
**    delay(500);**
**  }**
** **
**  else if(button7State == HIGH && total3>0)**
**  {**
**    total3= total3 - ten;**
**    total = total1 + total2 + total3 + total4+ total5+total6;**
**    Serial.println("Amount deleted.");**
**    Serial.println(total);**
**    tone(buzzer, 1000);**
**    delay(500);**
**    noTone(buzzer);**
**    delay(500);**
**  }  **
** **
**  else if(button7State == HIGH && total4>0)**
**  {**
**    total4 = total4 - twenty;**
**    total = total1 + total2 + total3 + total4+ total5+total6;**
**    Serial.println("Amount deleted.");**
**    Serial.println(total);**
**    tone(buzzer, 1000);**
**    delay(500);**
**    noTone(buzzer);**
**    delay(500);**
**  }**
** **
**  else if(button7State == HIGH && total5>0)**
**  {**
**    total5 = total5 - coin;**
**    total = total1 + total2 + total3 + total4+ total5+total6;**
**    Serial.println("Amount deleted.");**
**    Serial.println(total);**
**    tone(buzzer, 1000);**
**    delay(500);**
**    noTone(buzzer);**
**    delay(500);**
**  }**
** **
**  else if(button7State == HIGH && total6>0)**
**  {**
**    total6 = total6 - half;**
**    total = total1 + total2 + total3 + total4+ total5+total6;**
**    Serial.println("Amount deleted.");**
**    Serial.println(total);**
**    tone(buzzer, 1000);**
**    delay(500);**
**    noTone(buzzer);**
**    delay(500);**
**  }**
**  delay(10); // Delay a little bit to improve simulation performance**


  if (button8State == HIGH)
  {
    total = 0; total1 = 0; total2 = 0; total3 = 0; total4 = 0; total5 = 0; total6 = 0;
    Serial.println("Thank You!");
    tone(buzzer, 1000);
    delay(500);
    noTone(buzzer);
    delay(500);
  }
  delay(10); // Delay a little bit to improve simulation performance
}
2

Welcome to the forum

Is this the code where you attempted to add the cancellation code ? If not, then please post it and explain the problem

By the way, the code wold be much neater if you used arrays

3

I would probably have gone about it a different way, but within the paradigm you chose I would probably have a variable called "thisTransaction" in each of the if's, like for example:

if (button4State == HIGH)
  {
    thisTransaction = twenty;
    total4 = total4 + thisTransaction;

Then in the code for my "undo" button I'd subtract thisTransaction from the total.

Something like that anyway- that's a bit off the top of my head.

4

I think you'd better maintain the standard format of if, else if and else loops.

5

Thank you,

I have edited the code. Added the code I used to subtract/undo the last pressed button. If I press more than one button and then press the button for subtracting, it subtracts the value which was pressed first and then second not the last one. I want to cancel the button pressed most recently.

6

thank you,

I tried this and it didn't work.

7

Hi,
See if this code meets your need:

//This is a code for buttons

#include <SPI.h>
int b1 = 5;
int b2 = 6;
int b3 = 9;
int b4 = 10;
int b5 = 11;
int b6 = 12;
int b7 = 13;
int b8 = A0;

double coin = 0.1;
double half = 0.5;
int one = 1;
int five = 5;
int ten = 10;
int twenty = 20;
int confirm = 0;
int del = 0;

double total1 = 0.0;
double total2 = 0.0;
double total3 = 0.0;
double total4 = 0.0;
double total5 = 0.0;
double total6 = 0.0;
double total = 0.0;
double ftot = 0.0;

const int buzzer = A1;

bool flagBt1 = false;
bool flagBt2 = false;
bool flagBt3 = false;
bool flagBt4 = false;
bool flagBt5 = false;
bool flagBt6 = false;
bool flagBt7 = false;
bool flagBt8 = false;
//--------------------------------------------------------------------------
void myTone()
{
  tone(buzzer, 1000);
  delay(500);
  noTone(buzzer);
  delay(500);
}
//--------------------------------------------------------------------------
void setup()
{
  pinMode(b1, INPUT);
  pinMode(b2, INPUT);
  pinMode(b3, INPUT);
  pinMode(b4, INPUT);
  pinMode(b5, INPUT);
  pinMode(b6, INPUT);
  pinMode(b7, INPUT);
  pinMode(b8, INPUT);
  pinMode(buzzer, OUTPUT);
  Serial.begin(9600);
}
//--------------------------------------------------------------------------
void loop()
{
  // check if pushbutton is pressed.  if it is, the
  // button1State is HIGH

  if (flagBt1 == false)
  {
    flagBt1 = true;
    if (digitalRead(b1) == HIGH)
    {
      total1 = total1 + one;
      Serial.print("Pay  ");  Serial.print("1");  Serial.println("?");
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.print("Total = ");  Serial.println(total);
      ftot = ftot + total;
      myTone();
    }
    else
    {
      digitalWrite(buzzer, LOW);
    }
    delay(10); // Delay a little bit to improve simulation performance
  }

  if (flagBt2 == false)
  {
    flagBt2 = true;
    if (digitalRead(b2) == HIGH)
    {
      total2 = total2 + five;
      Serial.print("Pay ");  Serial.print("5");  Serial.println("?");
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.print("Total = ");  Serial.println(total);
      ftot = ftot + total;
      myTone();
    }
    else
    {
      digitalWrite(buzzer, LOW);
    }
    delay(10); // Delay a little bit to improve simulation performance
  }

  if (flagBt3 == false)
  {
    flagBt3 = true;
    if (digitalRead(b3) == HIGH)
    {
      total3 = total3 + ten;
      Serial.print("Pay  ");  Serial.print("10");  Serial.println("?");
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.print("Total = ");  Serial.println(total);
      ftot = ftot + total;
      myTone();
    }
    else
    {
      digitalWrite(buzzer, LOW);
    }
    delay(10); // Delay a little bit to improve simulation performance
  }

  if (flagBt4 == false)
  {
    flagBt4 = true;
    if (digitalRead(b4) == HIGH)
    {
      total4 = total4 + twenty;
      Serial.print("Pay "); Serial.print("20");   Serial.println("?");
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.print("Total = ");  Serial.println(total);
      ftot = ftot + total;
      myTone();
    }
    else
    {
      digitalWrite(buzzer, LOW);
    }
    delay(10); // Delay a little bit to improve simulation performance
  }

  if (flagBt5 == false)
  {
    flagBt5 = true;
    if (digitalRead(b5) == HIGH)
    {
      total5 = total5 + coin;
      Serial.print("Pay  "); Serial.print("0.1"); Serial.println("?");
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.print("Total = ");  Serial.println(total);
      ftot = ftot + total;
      myTone();
    }
    else
    {
      digitalWrite(buzzer, LOW);
    }
    delay(10); // Delay a little bit to improve simulation performance
  }

  if (flagBt6 == false)
  {
    flagBt6 = true;
    if (digitalRead(b6) == HIGH)
    {
      total6 = total6 + half;
      Serial.print("Pay ");  Serial.print("0.5");   Serial.println("?");
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.print("Total = ");  Serial.println(total);
      ftot = ftot + total;
      myTone();
    }
    else
    {
      digitalWrite(buzzer, LOW);
    }
    delay(10); // Delay a little bit to improve simulation performance
  }

  if (flagBt7 == false)
  {
    flagBt7 = true;
    if (digitalRead(b7) == HIGH && total1 > 0)
    {
      total1 = total1 - one;
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.println("Amount deleted.");
      Serial.println(total);
      myTone();
    }

    else if (digitalRead(b7) == HIGH && total2 > 0)
    {
      total2 = total2 - five;
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.println("Amount deleted.");
      Serial.println(total);
      myTone();
    }

    else if (digitalRead(b7) == HIGH && total3 > 0)
    {
      total3 = total3 - ten;
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.println("Amount deleted.");
      Serial.println(total);
      myTone();
    }

    else if (digitalRead(b7) == HIGH && total4 > 0)
    {
      total4 = total4 - twenty;
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.println("Amount deleted.");
      Serial.println(total);
      myTone();
    }

    else if (digitalRead(b7) == HIGH && total5 > 0)
    {
      total5 = total5 - coin;
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.println("Amount deleted.");
      Serial.println(total);
      myTone();
    }

    else if (digitalRead(b7) == HIGH && total6 > 0)
    {
      total6 = total6 - half;
      total = total1 + total2 + total3 + total4 + total5 + total6;
      Serial.println("Amount deleted.");
      Serial.println(total);
      myTone();

    }
    delay(10); // Delay a little bit to improve simulation performance
  }

  if (flagBt8 == false)
  {
    flagBt8 = true;
    if (digitalRead(b8) == HIGH)
    {
      total = 0; total1 = 0; total2 = 0; total3 = 0; total4 = 0; total5 = 0; total6 = 0;
      Serial.println("Thank You!");
      myTone();
    }
    delay(10); // Delay a little bit to improve simulation performance
  }
}
8

I uploaded the code you shared in the arduino ide. But serial monitor is blank. Pressing the buttons is not showing any result in the serial monitor.

9

Have you selected 9600 baud rate when opening the serial monitor?

10

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