Holding a String in a variable and changing it??

Using Arduino Programming Questions
#1

Hey there, so I am VERY new to this programming language and have just started using Arduino. I have run the LCD example sketch yet I want to try something different. I want the screen to display a string, wait, change it to a new one, wait and change and so on and so on in a loop.

Being that I don’t really know what I am doing I sort of GUESSEd at teh code and of course it won’t compile, would someone mid looking at the code and trying to see if they understand what I want to do and how to change it? THANKS IN ADVANCE!!!

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
}

void loop() {
  // set the cursor to column 0, line 0
  // (note: line 1 is the second row, since counting begins with 0):
   char mystring[16];
    lcd.setCursor(0, 1);
  // print the value of mystring and alternate its value
  lcd.print(mystring);
  {
    delay(115);
    mystring = "So, i gotta say";
    delay(115);
    mystring = "that lcds.";
    delay(115);
    mystring = "Really Do.....";
    delay(5000);
    mystring = "Kick Butt!!!!";
  }
    
    
}
#2 
   char mystring[16];
    lcd.setCursor(0, 1);
  // print the value of mystring and alternate its value
  lcd.print(mystring);

myString does not have a value at this point.

    mystring = "So, i gotta say";

You can’t assign a value to an array this way.

The strcat() function is worth looking at.

#3

I have neither Arduino nor LCD with me at the moment, but...

I think to change and display the string you need to do two things:

strcat (mystring,"So, i gotta say") ; lcd.print(mystring);

Though probably you could also do:

lcd.print("Hello");

Anyway even if you change the string you need to tell the lcd that it is changed by calling lcd.print.

...I have neither Arduino nor LCD with me at the moment.

#4

So I updated my code to the following and am still getting an error at the lcd.print(mystring); line saying mystring was not declared in this scope:

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);
void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
}

void loop() {
  lcd.setCursor(0, 1);
  lcd.print(mystring);
  {
    strcat (mystring, "So, i gotta say");
    delay(115);
    strcat (mystring,"that lcds.");
    delay(115);
    strcat (mystring,"Really Do.....");
    delay(115);
    strcat (mystring,"Kick Butt!!!!");
    delay(5000);
  }
    
    
}

Not sure what to do, I can’t see what is wrong with my syntax…

#5

If I understand you right, what you need is a simple function:

loop()
{
   myLCDprint("So, i gotta say");
   myLCDprint("that lcds.");
  etc....
}

void myLCDprint(mystring)
{
  lcd.print(mystring);
}

Job done (for now)

Geoff

#6

am still getting an error at the lcd.print(mystring); line saying mystring was not declared in this scope:

Please point out where you declared/defined mystring.

void myLCDprint(mystring)
{
  lcd.print(mystring);
}

Job done (for now)

At least until you try to compile.

#7

Oops, sorry,

Should have been :

void loop()
{
   myLCDprint("So, i gotta say");
   myLCDprint("that lcds.");
  etc....
}

void myLCDprint(String mystring)
{
  lcd.print(mystring);
}

which compiles OK on my Uno

Geoff

#8

Ok… I trried that in my sketchand I am still getting errors, I am not familliar with the myLCDprint function etc here is where my code is at after the latest additions":

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
}

void loop() {
    lcd.setCursor(0, 1);
{
   myLCDprint("So, i gotta say");
   myLCDprint("that lcds.");
}

void myLCDprint(String mystring)
{
  lcd.print(mystring);
}
    
}

I am getting a myLCDprint is not declared in this scope in the beginning void loop() function

any idea what can be done to this code to fix it?

#9

Where was it suggested that you should put the myLCDprint method INSIDE the loop function?

#10

In the previous reply. Aside from that do you know how I could change this script to acomplish this task?

#11

In the previous reply.

No. In that reply, the function is clearly AFTER loop.

Your code has more { and } than are needed. The extra ones makes it appear as though the function is in the right place, but it isn't.

#12

So I changed it to this yet it still tells me myLCDprint is not declared
Can somone show me what I need to cahnge and how in this sketch? I am not experienced with syntax yet at all, so I could really use some help.

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() 
{
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
}

void loop() 
{
   lcd.setCursor(0, 1);
   myLCDprint("So, i gotta say");
   myLCDprint("that lcds.");
void myLCDprint(String mystring)
{
  lcd.print(mystring);
}
}
#13

void loop()
{
lcd.setCursor(0, 1);
myLCDprint(“So, i gotta say”);
myLCDprint(“that lcds.”);
void myLCDprint(String mystring)
{
lcd.print(mystring);
}
}
The highlighted braces define the start and end of the loop function. Can you see that your function is defined INSIDE the loop function, which is not valid?

#14

so how do I need to re write this to fix it.

#15

so how do I need to re write this to fix it.

Move the function OUT of loop. void loop() { lcd.setCursor(0, 1); myLCDprint("So, i gotta say"); myLCDprint("that lcds."); } void myLCDprint(String mystring) { lcd.print(mystring); }

#16

as PaulS stated.. you can NOT nest your function inside your LOOP() rouinte/function..

void loop(){
   lcd.setCursor(0, 1);
   myLCDprint("So, i gotta say");
   myLCDprint("that lcds.");
}


void myLCDprint(String mystring){
  lcd.print(mystring);
}
#17

It can be confusing at the beginning. Once you know it is hard to remember when you did not know, though some people here seem to think they leapt from the womb already fully formed and experienced programmers. They seem to tease more than help.

Your mistake is that the function is inside the loop. Note that “inside” does not mean “after”. Inside means between the { and } which form the function called loop.

void Function ()
{
  everything here is "inside" the function.
  You need to count the opening and closing brackets to
  see where the loop ends.
  {
     some more stuff, but still inside Function
  }
}

Ah! Now I am outside Function.

Here is how to put it outside loop.

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() 
{
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
}

void myLCDprint(String mystring)
{
  lcd.print(mystring);
}

void loop() 
{
   lcd.setCursor(0, 1);
   myLCDprint("So, i gotta say");
   myLCDprint("that lcds.");
}

The above code is not supposed to compile and run, but illustrates how you should define functions.

#18

They seem to tease more than help.

This may simply be a consequence of "teach a man to fish" and "I don't plan to do your homework for you" (which is really another variant of the fish example), rather than any more sinister intent. For Arduino sketches, which tend to be pretty simple, it can be hard to find a balance between helping someone along and just giving a finished solution.

#19

I suppose thats one opinion.

for me.. dont bother posting at all if you dont plan to help.

This being a help forum and posting in the newbie./help sections.. it leads one to believe that IS the place to get 'help' and not lip service.

I understand teaching a man to fish.. but that comes with educating them on how to do so.. so NEXT TIME they understand and can do so themselves.

comments (which are by large the trend in which MANY vet members respond) like:" Than you thought wrong" or " someone doesnt understand correctly" "someone has more reading to do".. and the list is so long is stupid remarks that took longer to post than actually providing help, that there just isnt enough time.

Do nothing but promote a bad attitude and image of the forum.. they dont teach anyone anything.. much less on how to become self-reliant due to the 'learning' they got.

and EASY is a relative term.. people who are new, it might NOT be easy for them.

IMHO, its better for a post to go ignored then post something snarky or not helpful... but just ++ to post count.. and perpetuate a bad image.

Not everyone is like that.. and I suppose its a learning curve for both parties.. those trying to learn.. as well as those trying to teach.. it just seems MANY members her DO forget they had to learn too (just because they've been EE's for XX years)...

Dont have answers or POSITIVE links to share them help the OP.. then just skip the thread all together! :)

#20

wildbill:

They seem to tease more than help.

This may simply be a consequence of “teach a man to fish” and “I don’t plan to do your homework for you” (which is really another variant of the fish example), rather than any more sinister intent. For Arduino sketches, which tend to be pretty simple, it can be hard to find a balance between helping someone along and just giving a finished solution.

Sort of right, but there was a post which said “Who told you to put the function inside another function” which was clearly not going to be helpful to an absolute beginner. It maybe made the poster feel superior, but was clearly not intended to help the original poster.

Can you not remember having difficulties in a new subject?

You are right that we can’t post full solutions, but fragments of examples are much better than cryptic replies.