Quick Start
This board needs no library and no code of its own. It carries your existing I2C bus over an Ethernet cable, so you keep using the code you already have for the sensor or device at the far end. You need two of these boards, one at each end of the cable.
1. Connect the breakout board
Start with the local board, the one next to your microcontroller. Plug a Qwiic cable from your microcontroller into the Qwiic connector. If your controller has no Qwiic connector, wire the left header instead:
| Controller | Soldered Qwiic I2C Long Range Extender LTC4331 |
|---|---|
| 3.3 V | 3V3 |
| GND | GND |
| SDA | SDA |
| SCL | SCL |
Leave REMOTE unconnected. The local side is the default mode.
The board works at 3.3 V only. Do not connect 5 V.
2. Set up the board at the far end
On the second board, connect the REMOTE pin to 3V3. This makes it the remote
side, which drives the I2C devices attached to it. Plug your I2C device into its
Qwiic connector, or wire it to the SDA, SCL, 3V3 and GND pins of the left
header.
The Ethernet cable carries 3V3 and GND together with the data pair, so the
remote board is powered through the cable and needs no supply of its own.
3. Join the boards with an Ethernet cable
Plug a standard Ethernet cable into the RJ45 jack on each board. Both boards ship
with the link set to 1 MHz, which reaches up to 30 m. For a longer cable, lower
the speed with the SPEED1 and SPEED2 jumpers, as described in
Hardware Details.
4. Check the result
The LINK pin goes low once the two boards have found each other. It is
open-drain, and the default setting of JP7 gives it a pull-up, so you can read it
with a multimeter or a controller pin.
Devices at the far end now answer at their usual I2C addresses, as if they were on the same bus as your controller. An I2C scan from your controller lists them. The LTC4331's own control device is also on the local bus, at 0x77 by default.
5. If it does not work
Continue with Troubleshooting and retry after each change.