I2C SSD1306 does not work in Arduino Leonardo

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(writing for documentation sake, hoping this helps other users)

Arduino board:

• Arduino Leonardo

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

• Every SSD1306 library

  List the steps to reproduce the problem below:

• I have a working code with Arduino Uno,

• The very same code doesn't work with Arduino Leonardo.

• The display stays blank

• Evaluating the code, it never gets past the display initialization display.begin(SSD1306_SWITCHCAPVCC, 0x3C); instruction

• It also doesn't throw the error on Serial.println(F("SSD1306 allocation failed"));

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Root cause

My setup was using the GPIO port 2. After further investigation, I found in this picture that GPIO lines 2 and 3 are bridged to the ports SCL and SDA in the Arduino Leonardo. Essentially, it was conflicting and hampering the I2C operations.

Resolution

By moving my GPIO ports (and fixing the code) to somewhere else fixed the issue and the display now works nicely.