display.begin() always true

[NuclearPhoenixx]

Hi there! I have an issue where the display.begin() function will always return true regardless if there is an actual display plugged in or not. It works fine if there is a display, of course, but if there is none it doesn't register that and thinks there still is one.

• Arduino board: Raspberry Pi Pico with arduino-pico core

• Arduino IDE version (found in Arduino -> About Arduino menu): 2.0.1

• List the steps to reproduce the problem below (if possible attach a sketch or
  copy the sketch code in too):

  • Load the ssd1306_128x64_i2c example.
  • Upload.
  • Serial.println(F("SSD1306 allocation failed")); will never show because display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS) will never be false.
  • That's literally it for me. Nothing more, that easy.

Maybe it's got something to do with the Raspberry Pi Pico? I don't think so tbh, because everything else works fine, so there must be an issue here.

[nyckidryan]

I can confirm this is the case on ESP32-WROOM-32 38 pin dev module as well, in Arduino IDE 1.8.19 and 2.0.1.

[PitHerm]

Yes, i display.begin returns always TRUE
on Pi Pico , ESP8266 , ESP32

[PitHerm]

Well, i digged around within the source code of the lib and found NO return of FALSE if the display is not avaiable !

I thought about a workaround and here is the tested and working result:
Wire.begin();
Wire.beginTransmission (SCREEN_ADDRESS);
if (Wire.endTransmission () > 0){
Serial.println("SSD1306 allocation failed");
for(;;); // Don't proceed, loop forever
}
Wire.end();
if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
Serial.println(F("SSD1306 FAIL: Buffer allocation error, not enough memory"));
for(;;); // Don't proceed, loop forever
}

instead of:
if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
Serial.println(F("SSD1306 allocation failed"));
for(;;); // Don't proceed, loop forever
}

Additional Info:

if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
Serial.println(F("SSD1306 allocation failed"));
for(;;); // Don't proceed, loop forever
}

works but NOT as expected , it only returns FALSE if not enough memory for display buffer is avaiable.
so it would be better to change the phrase " Serial.println(F("SSD1306 allocation failed")); " to
" Serial.println(F("SSD1306 FAIL: Buffer allocation error, not enough memory")); "

[NuclearPhoenixx]

Well, i digged around within the source code of the lib and found NO return of FALSE if the display is not avaiable !

Yes, it's clearly an issue. The only time false would be returned is in the case that the display buffer fails to be allocated. Other than that, it seems to always execute to the end of the function and return true. I wonder if there is no way to check the display via I2C to see if it has connected properly, there must be a way...