Re: Question about the usage of F()

[johnwasser]

F() casts a PROGMEM character string as type __FlashStringHelper. .print() uses that as a cue to know that the argument is a disguised PROGMEM character string. If you pass that to a function that takes a regular character pointer you SHOULD get a compiler error (__FlashStringHelper is not a pointer). To make your function work I think you need to write it like this:

void repeaterPrint(int counter, __FlashStringHelper text)
{
  for (int i = 0; i < counter; i++)
  {
    Serial.println(text);
  }
}

void loop()
{
   repeaterPrint(5, F("Hello World"));
}

Similarly, to declare an array of PROGMEM strings that you can Serial.print() you need to use the __FlashStringHelper type:

__FlashStringHelper string_table[] = 
{
   F("String 1"),
   F("String 2"),
   F("String 3")
}

[johnwasser]

And I don't need the PROGMEM keyword for any of that?

The PROGMEM keyword is in the F() macro and in the Print object.

Delta_G:
And on the function example, if I want it to be able to work with either RAM or flash, I could just use an overload one with char* and one with __FlashStringHelper?

Yes, I think that will work.

[system]

avr-gcc seems to not like the F() syntax in the array initialization
__FlashStringHelper string_table[] =
{
F("String 1"),
F("String 2")
}
and complains
tst.cpp:25:8: error: statement-expressions are not allowed outside functions nor in template-argument lists

[system]

This is a snippet I used that works in 1.0:

const __FlashStringHelper* options = reinterpret_cast <const __FlashStringHelper *>
(
    "blahblahblah"
);

and calling Serial.print(options); prints it.

[kllsamui]

WizenedEE:
This is a snippet I used that works in 1.0:

const __FlashStringHelper* options = reinterpret_cast <const __FlashStringHelper *>

(
    "blahblahblah"
);

and calling Serial.print(options); prints it.

sorry i dont get it WizenendEE

void setup() {
  Serial.begin(57600);
  Serial.print(F("TEST "));
  
const __FlashStringHelper* options = reinterpret_cast <const __FlashStringHelper *> 
(
    "blahblahblah"
);
Serial.print(options);
}

void loop(){

}

gives here

TEST $/???O????ï?ÿ?@?Æ

[system]

Interesting. I do remember having some problems with it, which I guess were related to it not actually putting it in the program memory. That's something to work off of, though.