Variables displayed incorrectly

Question

I am making a keypad and when I try to save the buttons that were pushed they reset back to zero.

int tmp = 1;
int digit = 1;
int a = 0;
int b = 0;
int c = 0;
int d = 0;
int code = 0;
void setup() {
 Serial.begin(9600);
 pinMode(7, INPUT);
 pinMode(2, INPUT);
 pinMode(3, INPUT);
 pinMode(4, INPUT);
 pinMode(5, INPUT);
 pinMode(6, INPUT);
 pinMode(9, OUTPUT);
 pinMode(8, OUTPUT);
}
void loop() {
 if (digit > 4) {
 digit = 1;
 }
 for (int i = 2; i <= 7; i++) {
 int tmp = digitalRead(i);
 if (tmp == HIGH) {
 if (digit == 1) {
 int a = i - 1;
 }
 if (digit == 2) {
 int b = i - 1;
 }
 if (digit == 3) {
 int c = i - 1;
 }
 if (digit == 4) {
 int d = i - 1;
 Serial.print(a);
 Serial.print(b);
 Serial.print(c);
 Serial.print(d);
 digitalWrite(8, HIGH);
 }
 digitalWrite(9, HIGH);
 delay(100);
 digitalWrite(9, LOW);
 delay(100);
 Serial.print(i);
 digit++;
 }
 }
}

• Jot: There is a library for a keypad: github.com/Chris--A/Keypad If you want to make your own code, you have to specify what you want: should multiple keys presses at the same time being detected ? should there be debouncing ? do you want to know how long a key is pressed ?
• Nathan Anderson: I already have key detection but for some reason when I have it output variables A B C and D it only stores the last digit and the rest are 0
• Code Gorilla: @NathanAnderson - The compiler would be warning you about the issue, but warnings are turned off in the Arduino IDE by default.
• 001: You can make your code more flexible by keeping a running total (int total = 0;) and just add to it with each keypress: total = (total * 10) + i; - where i is the most recent digit input by the user.

Answer 1

Do you know what int a; does?

For example you have a global variable a and then you have local a. Local one hides global one.

In all cases you're changing local variables. Then you're printing global a,b,c and local d.