Uart breakout board for SPIKE and EV3 – OpenMV compatible


SKU: LMS-uart-convertor-1.0 Category:


This convertor board is the swiss army knife of uart connections for your LEGO MINDSTORMS EV3, Robot Inventor, and SPIKE Prime models. The LMS/SPIKE OpenMV converter connects your SPIKE Prime to your OpenMV camera board, or to the esp-i2c-wifi board.

In the converter breadboard package you will find:

  • 2×8 pin headers, 0.1 inch pitch
  • a grove port
  • 2x 6 pin ports
  • 2x 6 pin plugs
  • 1x Wedo 2.0 or LEGO Power Functions 2.0 wire.

The 6 pin plug shrinks perfectly on a repurposed Wedo or Power Functions 2.0 wire, no tools needed! I ordered the wires online from China. One is included in the kit, you can order a second one yourself.


Ultimate connectivity for all your LEGO bricks

In the wiki and projects repository, we are continuously adding manuals and example projects with this board. We haven’t made examples for everything yet, but with the design of the board, we had these connections in mind:

  • SPIKE/RI to SPIKE/RI uart connection
  • SPIKE/RI to EV3 uart connection
  • SPIKE/RI to OpenMV uart connection
  • EV3 to OpenMV uart connection
  • SPIKE/RI to ESP WiFi board with i2c
  • OpenMV i2c on pins 7 & 8 to grove or 0.1″ headers

The EV3/SPIKE OpenMV convertor board has the following applications:

  • Connect a WiFi ESP board to your SPIKE Prime or Robot Inventor hub
  • Connect an OpenMV AI camera to your SPIKE Prime, Robot Inventor or EV3 hub.
  • Create wired communication between all your Lego Power Functions 2.0 and NXT/Ev3 devices

LMS-uart-convertor 1.0 pinout

In the pinout, you can see that the board makes all uart rx/tx connections. The I2C connections require a board below this board. That could be an OpenMV camera or an ESP wifi board. LEGO smart hubs have internal resistors that mess with pull-up resistors in the most common i2c devices, so they are hard to connect directly. You can also use jumper wires and headers at the bottom of the board to connect LEGO line 6 to SDA and LEGO line 5 to SCL.

Because motor lines (lines 1 and 2) can generate up to 9V, they are not connected by default. The board has soldering jumpers to connect them. The motor lines can be handy to power LED arrays that take a lot of current. Be careful not to fry any 4v7 or 3v3 logic when you do.

Here’s one of my experiments where I use the board:

Warning: there’s no warranty for this product!

Soldering guide:


We have been very careful designing this breakout board, to make it near impossible to create connections that damage your LEGO. Nonetheless, incorrect usage of this board could damage your LEGO in such a way that your LEGO warranty is void. This is a hacker’s tool. We do not guarantee the safety of your LEGO hubs or any electronic devices you connect with this breakout board. Do not use voltages higher than 9v, for your safety and the safety of your electronics. Making the right connections is your responsibility. This product is provided ‘as is’ without warranty of any kind, either express or implied, including, but not limited to, the implied warranties of fitness for a purpose, or the warranty of non-infringement. Buying this product means you agree with this disclaimer.

Additional information

Weight0.05 kg
Dimensions10 × 10 × 1 cm
Pack size

Single, Three Pack


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Uart breakout board for SPIKE and EV3 – OpenMV compatible