diagnose-i2c

# /diagnose-i2c — I2C Bus Troubleshooting Systematic checklist for I2C problems on the ESP32 with AS5600 + SSD1306 OLED. ## Expected I2C devices | Address | Device | Purpose | |---------|--------|---------| | 0x36 | AS5600 | Rudder angle sensor | | 0x3C | SSD1306 | OLED display | Both share GPIO 21 (SDA) and GPIO 22 (SCL). No external pull-ups needed — both modules have built-in pull-ups. ## Diagnostic questions Ask the user and work through these in order: ### 1. Power - Is the ESP32 power LED on? - Are both modules connected to 3.3V (NOT 5V)? - Is the 3.3V rail actually powered? (A common breadboard issue — the power rails may not be connected end-to-end) ### 2. Wiring - SDA on both modules goes to GPIO 21 (labeled D21 on most ESP32 boards) - SCL on both modules goes to GPIO 22 (labeled D22) - Check the pin labels on the OLED module — order varies between manufacturers. Common: GND, VCC, SCL, SDA (left to right) - Ensure wires are firmly seated in the breadboard ### 3. Isolation test - Disconnect the AS5600, leave only the OLED connected - Power cycle the ESP32 - Does the OLED show "RudderAngle / Starting..."? - If yes: reconnect AS5600 and test again - If no: the OLED wiring is wrong ### 4. Serial log errors - `i2cWriteReadNonStop returned Error 263` — I2C NACK, device not responding at that address. Check power and wiring. - Errors in pairs every ~200ms — both sensor reads (10 Hz) and display updates (5 Hz) are failing; likely a bus-wide problem (power or SDA/SCL) - Intermittent errors — possible bus contention or loose breadboard wire ### 5. If nothing works - Try a different ESP32 board - Try different jumper wires (breadboard wires go bad) - Check solder joints on the module header pins