Communication Troubleshooting
Fix I2C, Serial, and Wi-Fi connectivity problems
I2C Connection Issues
Symptoms
- Errors like
OS Error: [Errno 5] EIO - Diagnostics report "PCA9685 not found"
- No I2C devices show up during a scan
Checklist
SDA/SCL Swap
Verify SDA is connected to GP1 and SCL to GP0. Swapping these is the most common error.
Common Ground
Ensure the Ground pin on the Pico is connected to the Ground pin on the PCA9685.
Pull-up Resistors
The PCA9685 usually has 10k pull-ups built-in. If you have very long wires, you might need stronger (lower value) external pull-ups.
Cannot Connect to REPL
If you cannot access the MicroPython prompt through Thonny or mpremote:
Try a different USB cable
Many Micro-USB cables are for charging only and do not have data lines. Use a known-good data cable.
Check Driver/Permissions
On Linux, ensure your user is in the dialout group. On Windows, check Device Manager for the COM port.