Simple Keypad Input to Screen Problem

Projects General Guidance
1

I have a program that works, until I type "#" which I thought would only have made the char str[17] equal to 16 spaces again, but when I press "#" the first column of the keypad stops responding.

What am I doing wrong here?

I thought I was being safe using char to hold the 17 length string instead of String, but I must be affecting the program to make it misbehave.

#include <Keypad.h>
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,20,4); 
const byte ROWS = 4; //four rows
const byte COLS = 4; //three columns
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
char str[17]="                ";
byte rowPins[ROWS] = {5, 4, 3, 2}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {9, 8, 7, 6}; //connect to the column pinouts of the keypad
int d=0;
Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

void setup(){
  Serial.begin(9600);
  lcd.init();                      // initialize the lcd 
  lcd.init();
  // Print a message to the LCD.
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("PLAY SONG NUMBER....");
  lcd.setCursor(0,1);
  lcd.print("");
  lcd.setCursor(0,2);
  lcd.print("");
  lcd.setCursor(0,3);
  lcd.print("");
}

void loop(){

  char key = keypad.getKey();
  if (key=='#'){
    str[17]="                ";
    d=0;
  }
  if (key and key!='#' and d<16){
    Serial.println(key);
  str[d] = key;
  d=d+1;
  Serial.println(d);
  lcd.setCursor(0,3);
  lcd.print(str);
  }
}
2

No, that's not how it's done.

Try

strcpy(str, "                ");
3

One obvious problem is this

        str[17] = "                ";

You are trying to write 16 characters to the eighteenth position in an array

Also, the str array which you seem to want to use to hold a string never has a terminating zero character added to it so there is no obvious end marker on the string

4

Won't this do it?

5

Thats a beginners mistake. The array is defined to have 17 elements, indexed from 0 up to 16. Writing at index 17 is outside the array, into some unknown area, likely used for other things.

6

It is true that creates an array with 16 space characters and the terminating zero but we have no idea how many characters are being entered from the keypad and/or whether the resulting string should have trailing spaces or not

Then, of course, there is the problem of

        str[17] = "                ";
7

You can see in the program that no more that 16 characters are being written from the keyboard.

They are ignored if they are pressed.

8

I have made a change as suggested, and now it will not print "CLEARED SCREEN" to screen when I press "#". Is this expected behaviour?

#include <Keypad.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);
const byte ROWS = 4;  //four rows
const byte COLS = 4;  //three columns
char keys[ROWS][COLS] = {
  { '1', '2', '3', 'A' },
  { '4', '5', '6', 'B' },
  { '7', '8', '9', 'C' },
  { '*', '0', '#', 'D' }
};
char str[17] = "                ";
byte rowPins[ROWS] = { 5, 4, 3, 2 };  //connect to the row pinouts of the keypad
byte colPins[COLS] = { 9, 8, 7, 6 };  //connect to the column pinouts of the keypad
int d = 0;
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup() {
  Serial.begin(9600);
  lcd.init();  // initialize the lcd
  lcd.init();
  // Print a message to the LCD.
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("PLAY SONG NUMBER....");
  lcd.setCursor(0, 1);
  lcd.print("");
  lcd.setCursor(0, 2);
  lcd.print("");
  lcd.setCursor(0, 3);
  lcd.print("");
}

void loop() {

  char key = keypad.getKey();
  if (key == '#') {
    strcpy(str, "                ");
    lcd.setCursor(0, 3);
    lcd.print("CLEARED   SCREEN");
    d = 0;
  }

  if (key and key != '#' and d < 16) {
    Serial.println(key);
    str[d] = key;
    Serial.println(d);
    lcd.setCursor(0, 3);
    lcd.print(str);
        d = d + 1;
  }
}
9

What you say is true but is it OK for the string to have trailing spaces if only a few characters are entered ?

Have you fixed the problem with

        str[17] = "                ";
11

The 'string' is only getting used to print to the 20 width line of an LCD screen. That should be okay, shouldn't it?

13 
#include <Keypad.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);
const byte ROWS = 4;  //four rows
const byte COLS = 4;  //three columns
char keys[ROWS][COLS] = {
  { '1', '2', '3', 'A' },
  { '4', '5', '6', 'B' },
  { '7', '8', '9', 'C' },
  { '*', '0', '#', 'D' }
};
char str[17] = "                ";
byte rowPins[ROWS] = { 5, 4, 3, 2 };  //connect to the row pinouts of the keypad
byte colPins[COLS] = { 9, 8, 7, 6 };  //connect to the column pinouts of the keypad
int d = 0;
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup() {
  Serial.begin(115200);
  lcd.init();  // initialize the lcd
  lcd.init();
  // Print a message to the LCD.
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("PLAY SONG NUMBER....");
  lcd.setCursor(0, 1);
  lcd.print("");
  lcd.setCursor(0, 2);
  lcd.print("");
  lcd.setCursor(0, 3);
  lcd.print("");
}

void loop() {

  char key = keypad.getKey();
  if (key) {
  if (key == '#') {
    strcpy(str,"                ");
    lcd.setCursor(0, 3);
    lcd.print("CLEARED   SCREEN");
    delay(50);
    d = 0;
  }

  if (key != '#' and d < 16) {
    Serial.println(key);
    str[d] = key;
    Serial.println(d);
    lcd.setCursor(0, 3);
    lcd.print(str);
        Serial.println(sizeof(str));
            Serial.println(str);
        d = d + 1;
  }
  }
}
14

I don't see why you ever need to fill the array with blanks.

edit: I see what you are doing, never mind, that could work, just looks odd…


    str[d] = key;
    Serial.println(d);

And you need to keep putting the null terminator as you build it, viz:

    str[d] = key;
    str[d + 1] = '\0';
    Serial.println(d);

HTH

a7

15

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.