I want to convert const char array in PROGMEM to String. How do I do this?

const char charArray[] PROGMEM = "Some text";
  • If you mean a C++ style string, I think you just need to do this - stackoverflow.com/questions/8960087/…
    – Tri
    Aug 14, 2018 at 17:23
  • No, I want to convert this in Arduino-IDE. That is not work correctly! Aug 14, 2018 at 17:26
  • I just saw the answer and I had no idea that was even possible. I think that is your answer.
    – Tri
    Aug 14, 2018 at 17:38
  • Unfortunately that is not work. Thank you, however. Aug 14, 2018 at 17:54
  • 1
    what does this mean? that is not work .... that statement provides no useful information .... describing the actual error would help
    – jsotola
    Aug 14, 2018 at 19:51

1 Answer 1


you can use a cast to __FlashStringHelper to invoke the right constructor of the String class. It is the constructor which copies the char array from PROGMEM. __FlashStringHelper is intended as return type for the F() macro.

const char charArray[] PROGMEM = "Some text";

void setup() {


  String s((const __FlashStringHelper*) charArray);


void loop() {
  • That is right, but how do this in loop or another functions? Aug 14, 2018 at 17:51
  • PROGMEM is always global. and setup() is a function like every other so same way
    – Juraj
    Aug 14, 2018 at 17:54
  • Absolutely, but when I write this code in loop, the compiler will generate this error: conflicting declaration 'String s' Aug 14, 2018 at 17:58
  • Thanks so much. The compiler error was due to another part of my sketch. Aug 14, 2018 at 18:16

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