Troubleshooting
Start with the symptom you can observe. Apply one change at a time, then check the link again.
These entries come from the LTC4331 datasheet and the board's design.
| Symptom | Check | Fix |
|---|---|---|
LINK never goes low | The link is only reported when one board is local and the other is remote. | Leave REMOTE unconnected on the local board and tie it to 3V3 on the far board. Check that the Ethernet cable is fully seated at both ends. |
| Devices at the far end do not answer | The RDY pin goes low once the local board has joined the I2C bus. | Check RDY and LINK on the local board. If either stays high, fix the link first. |
| The link is unreliable or drops out | The cable is longer than the speed setting allows. | Lower the speed with the SPEED1 and SPEED2 jumpers. The datasheet lengths were measured with Cat5E cable in a lab, so your cable may reach less. |
| The board does nothing | If you drive ON from a controller pin, a low level puts the LTC4331 into low-power mode with its outputs disabled. | Keep ON high for operation. |
| A device on your bus clashes with the board | The LTC4331 has its own control device on the local bus, at 0x77 by default. | Change its address with the A1 and A2 jumpers, or open both to disable it. See Hardware Details. |
SLO behaves unpredictably | The datasheet says SLO must not float. | Make sure JP6 is bridged to GND or 3.3 V, not left open. |
| Interrupts from the far end are missing or noisy | ALERT is an input on the remote side and must not float there. | Give ALERT a defined level on the remote board. |
Still blocked?
Ask on the community forum. Include the following so someone can reproduce it:
- product name and SKU: Soldered Qwiic I2C Long Range Extender LTC4331,
333415 - controller board and software environment
- complete error text or unexpected output
- connection method, link speed setting and power source
- cable type and length
- a clear photo of the wiring