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Topic: Problem with 3*4 Keypad Again (Read 1 time) previous topic - next topic


Nevermind I solved the problem. I shouldn't have repeated the int. Nevertheless I still may need help with the keypad.


It's an accelerometer

What is?
A 3x4 keypad?
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.


Jul 19, 2010, 11:36 am Last Edit: Jul 19, 2010, 11:38 am by cowjam Reason: 1
Firstly, you seem to want four digits inputted but your FOR loops go from 0 to less than three.  Less than three is 2, so it goes 0,1,2.  

Secondly, you define a string as: charGain[4]
That means it has four chars in it.  Arrays start counting from 0 though, so the available characters in charGain are charGain[0], charGain[1], charGain[2] and charGain[3].
You add a character to charGain[4] which doesn't exist.

Thirdly, you have nested FOR loops using the same counter variable.  I think it'll work, but it's a bad idea.  It's really easy to get wrong and mess up your first loop, so you'd be better using a different variable then when complete terminate the loop.

You get the same character infinite times because you have no condition on it printing i.

Look through your LOOP: you've got a FOR loop, within which is an if (key != NO_KEY){ loop.
So, your FOR loop executes three times, if there's a keypress then it does something. If there is no keypress it doesn't executre that IF loop.  It doesn't wait for there to be a keypress, it just doesn't execute that for loop.

So it keeps looping, and it loops quickly.  Once you've pressed a key then it processes it, and afterwards it has a keypress in its variables so every time a key isn't pressed it doesn't do the IF A KEY HAS BEEN PRESSED bit and shoots straight to the end, where it prints the key it has.

Change that IF (key !=.. to something like (and this is a guesstimate, not guaranteed to work):
Code: [Select]
char key = kpd.getKey();
while (key == NO_KEY){
  key = kpd.getKey();
if (key = '#'){  

Then the rest of your code.

That while loop will hold the programme there until it gets a keypress and should solve your problem.


AWOL another guy asked a different question I had about an accelerometer, but I deleted most of those messages.


Code: [Select]
#include <Keypad.h>

const byte ROWS = 4;
const byte COLS = 3;

char keys[ROWS][COLS] = {

byte rowPins[ROWS] = {25, 35, 33, 29};
byte colPins[COLS] = {27, 23, 31};

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

void setup()

char charGain[4];
int charindex =0;
int i;

void loop(){

char key = kpd.getKey();
if (key != NO_KEY){
while (charindex < 4){
  if (key == '#'){
       while (charindex < 4){  //if the user didn't enter 4 digits float from the keypad, then other char in the array is set to be 0
      //   charindex=0;
  else if (key == '*'){
           charindex =0;
  else if (key != NO_KEY || '#' || '*'){      //if the user enter 0-9, then store it into array and display it
charGain[4] = '\0';
i = atoi (charGain);
/* for (charindex == 0;charindex < 4;charindex++){
   //lcd.print("array [" ++ charindex ++ "]"++ charGain[charindex]);
   Serial.print("array [");
   Serial.print("] ");
} */

Well I tried it again using this code and I'll either get the same number 4 times in a row, for example, if a 1 was pressed: 1111 or just a 0.

The # seems to clear it, so idk what the problem is there with either the * key or the # key or both.

I would appreciate any help though.

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