Friday, September 30, 2011

Microchip ICD adapter -> NXT port breakout board

Lego Mindstorms NXT kits are great for robotic prototypes and experiments. The computer brick and sensors communicate over I2C, which is great for DIY expansions. Unfortunately they also use nonstandard RJ connectors. (You can now buy the connectors, but that's no fun.)

The NXT's RJ port with offset connector lock.

I wanted to access the I2C, so I hacked up my "sound sensor" (microphone) to add a standard 0.1" header. But even as hacks go, it was ugly and only allowed access to 5 of the 6 pins.

However, a while ago the ECE department was getting rid of surplus parts, and among the reels of SMD resistors were a handful of header-to-RJ45 adapter boards that come with Microchip ICD programmers.

Microchip, on the other hand, make this handy board with a normal RJ45 port.
One day I happened to look at one and realize the RJ port on the Microchip board had the same pin spacing as the NXT ports. I cracked open my earlier hack, did a bit of soldering and desoldering, and boom - I had a small, clean NXT-port-to-header breakout board.

The connector lock may be shifted, but the footprint is the same as RJ45.
Mind you, I haven't actually coded up an I2C interface yet. But I can have a lot of lovely continuity beeps between NXT ports and a breadboard now. :)



  1. Awesome - but where did you procure the right-hand-adjustment RJ12 Socket?
    I sourced the cable ends easily, but still can't find a maker of the socket :/

  2. I used the original jack from the sound sensor, which I'd previously cracked open to add a header so I could access the I2C pins. That "solution" was ugly and cumbersome and I wanted something better. When I realized I could use the Microchip boards I desoldered the jack and used it for this board.