Arduino IDE problem - showString( )

Getting Started
7

There must be something about your installation that isn’t quite right.

This is a long shot:
Look through the Arduino installation instructions in Learn Learn | OpenEnergyMonitor and especially Learn | OpenEnergyMonitor just in case there’s something not in the correct place, though I don’t see how that would account for the error you’re seeing.

It comes back to the compiler can’t see the function:

static void showString (PGM_P s) {
  for (;;) {
    char c = pgm_read_byte(s++);
    if (c == 0)
      break;
    if (c == '\n')
      Serial.print('\r');
    Serial.print(c);
  }
}

yet it must be reading and parsing the file to generate the error message.
There has to be something wrong in the file above that function definition that’s preventing the compiler from finding it.
I’m using V1.8.1 under Ubuntu Linux, but I can’t see anything in the release notes that might be relevant.

You do want showString, because it gives you the help text for configuring & saving to EEPROM. If you can’t get it to work, commenting those two lines that throw the error should get you going.