progmem help

Projects Programming
1

Hi all, hope you can help. What is the correct way to read "HELLO2" from the code below?

prog_char hello[] PROGMEM =
{
  "HELLO1"
  "HELLO2"
  "HELLO3"
};

Many thanks.

2

Does that snippet even compile?

3

I don't get any errors apart from the line that says

sprintf_P(str1, hello[2]);

my full code below.

#include <avr/pgmspace.h>

prog_char hello[] PROGMEM =
{
  "HELLO1"
  "HELLO2"
  "HELLO3"
};
void setup()
{ 
 //Initialize serial and wait for port to open:
  Serial.begin(9600); 
  while (!Serial)
  {
    ; // wait for serial port to connect. Needed for Leonardo only
  }
}

void loop()
{
  char str1;
  
  sprintf_P(str1, hello[2]);
  
  Serial.print(str1);
  
  delay(5000);
}

Am wanting to have an array of strings and read them when i want. Just trying to learn about progmem.

4 
prog_char hello[] PROGMEM =
{
  "HELLO1"
  "HELLO2"
  "HELLO3"
};

This is what "hello" contains: "HELLO1HELLO2HELLO3" (a single C string)
If that's what you want, then it is easy to locate "HELLO2" - it starts at offset 6, and is 6 characters long.
It might be easier for you to store them as separate strings.

5

I have just noticed AWOL that my strings are not separate lol and thats what i want so i gues my code needs to be something like below

prog_char hello[] PROGMEM =
{
  "HELLO1",
  "HELLO2",
  "HELLO3"
};

so how would i read the second string?

6

I have worked it out now with the code below.

#include <avr/pgmspace.h>

prog_char hello[3][7] PROGMEM =
{
  "HELLO1",
  "HELLO2",
  "HELLO3"
};

void setup()
{ 
  Serial.begin(9600); 
  while (!Serial)
  {
    ;
  }
}

void loop()
{
  char str1[16];
  
  sprintf_P(str1, hello[2]);
  
  Serial.print(str1);
  
  delay(5000);
}
7

I have worked it out now with the code below.

If that code is printing "HELLO2", something is wrong. That should be printing "HELLO3".