[SOLVED] Tips on working with variable char Arrays

Projects Programming
1

I´m trying to wrap my head around working with text in arduino code. My current goal is to declare an array containing 8 string elements (not string objects as I´m starting to understand the drawback of these), and these elements needs to be editable but with a known max character len.

For a little background, i´m working on a menu system for an LCD and i´m sure there is a more clever way of doing this without arrays but this was a good excuse for me to learn how to use arrays. Even numbered elements will contain an attribute/effect of the text and the next (uneven) number will contain the text this will be applied to.

I´ve done extensive googeling and forum searching but it´s hard finding information on arrays containing strings but not string object. The following forum post got me going but does not explain how to properly edit the elements

http://forum.arduino.cc/index.php?topic=331337.0

This is what i have so far. It allows me to create an array and edit the first character of the elements with an ASCI number but id of course like to rewrite an entire array element without converting it to asci numbers.
Its running on an Mini Pro

#include <Arduino.h>
#include <LiquidCrystal.h>

char LcdRows[8][15]={{"blink"},{"row1"},{"scroll"},{"row2"},{""},{"row3"},{""},{"row4"}};

LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

void setup() {
  Serial.begin(9600);           // start serial for output

   lcd.begin(20, 4 );
   lcd.clear();

}

void loop() {


int LcdElement=0;
for (int i = 0; i < 4; i++){
lcd.setCursor(0, i);
lcd.print(LcdRows[LcdElement+1]);
Serial.println(LcdRows[LcdElement+1]);
LcdElement=LcdElement+2;
delay(200);


}

lcd.clear();
LcdRows[4][15]=99;  //turns a row in to a cow


//Me trying to bruteforce a solution

//LcdRows[4][15]='teeest';
//LcdRows[4][15]=char('teeest');
//LcdRows[6][15]=char ("test");
//LcdRows[6][]=char ("test");
//LcdRows[6][]="test";
}
2

Your odd and even scheme is like a two dimensional array. It will be difficult to keep track of which is which. You could store the strings and the attributes in two arrays. That will be more efficient if one type of element is a different size to the other.

LcdRows[0] is a pointer to the first character in the first string. You can print the string by passing this as a parameter to lcd.print(). You can pass it to any other function, like strncpy() which will copy strings between locations.

If you want to change that first character to an uppercase X then this code will do it:LcdRows[0][0] = 'X';
Anything with single quotes around it is a single char.

3

Agreed, a two dimensional array would make more sense but i opted for this solution because it seemed like an easier first step. If you have an hints on how I could do this with a two dimensional array it would be much appreciated.

I will play around with element 0 but to clarify, I dont want to only edit the first character of the string. I want to replace the original string with another string.
For example LcdRows[1][0]="new value";

4

Many thanks MorganS, strcpy solved the problem!

strcpy(LcdRows[1],"testing");