[originally published 19 July 2006 on todbot]
But if you want to hack together something similar and you don’t want to build a huge honking Roomba serial tether, you could build the Roombongle!
Things you’ll need to build the Roombongle:
– USB data cable for Nokia phones (aka “FutureDial Cable 22”) – $20
– Mini-Din 8-pin cable, Jameco #10604, $3.30
[Update: see comments below, you can get the USB data cable for $6.99!]
This puts the cost at about $24. A RooStick costs $29, but you also need their $17 cable, so $46. Roombongle is half the price, but it’ll take you about an hour to build. How much is an hour of your time worth? :)
The Roombongle is made from a phone sync cable. Out of the box it’s pretty unassuming:
Make sure the cable you get has the little bulge in the middle. That’s where the magic happens.
It turns out that if you take the little bulge apart, there’s a friendly little PL2303 USB-to-serial adapter chip inside:
You can download the spec sheet for said chip and you’ll see that it normally works at 3.3V, but its inputs are 5V-tolerant and its 3.3V outputs are within the valid range for 5V logic. Thus, the Roomba should understand it, and it should understand the Roomba. Obviously the thing to do next is graft a Roomba-compatible Mini-DIN 8-pin cable to it:
Just RX, TX, and GND are all that’s needed. You can route the +16V from the Roomba to an external connector if you want. That’s what the 9V connector-like thing is in the top photo. Once the wires are soldered down, just snap the case back together, use a little hot glue to seal in the Roomba cable and act as a strain relief, and you’re done.
Now with the Roombongle, your laptop is free to explore its surroundings, no longer reliant on you to carry it from place to place.
Thanks and Inspiration
The guys over at NSLU2-Linux did the hard work of figuring out these Radio Shack data cables. And not just the Nokia ones, but all the other sync cables RS sells.