Roomba Hacking via Serial Tether

Note:
This post is pretty old and I’ve been continuing work on Roomba software.
Note:
For a more readable take on this, see this Makezine artcicle

A week ago I got my OSMO//hacker Roomba firmware updater from iRobot. It worked like a charm, giving me a serial port to fully control the Roomba.

An interface was needed however, since the crazy mini-DIN 7-pin on the Roomba is very unstandard. So the first attempt at a robust interface between a Roomba and a standard PC serial port is my Roomba Serial Interface:

The Roomba Serial Connector
It seems people are confused by the mini-DIN 7-pin connector, citing difficulties in obtaining that specific plug. It turns out that mini-DIN 8-pin plugs will mechanically mate with the 7-pin jacks, with the center key hole in the 7-pin female jack taking the middel pin of the 8-pin plug. Mac high-speed serial cables from the 1990’s work great for this, and I have a ton of those from all my misspent youth doing MIDI on a Mac. So chop up those old Mac serial cables! If you can’t find one, Jameco will sell you one for $3.29.

The PC Serial Connector
Some computers have an RS-232 serial port. Most don’t. To hook this serial interface cable up to your Mac or other modern computer without an RS-232 port, use a Keyspan High Speed USB Serial Adapter. Supported on all platforms and the choice of Mac hardware-hackers worldwide.

Step-by-Step Construction details
If you’d like to build your own interface but don’t quite know where to start, I took a few images of the process I used.

The Software
With the Keyspan adapter and the Roomba Serial Interface, all the hardware is present to control the Roomba from a computer. All that’s required is software that can connect to serial ports and send and receive binary data. The Roomba SCI protocol isn’t text-based, so you can’t really use a normal terminal program like ZTerm (Mac) or HyperTerminal (PC).

My goal was to create a program that allowed one to remotely control all aspects of Roomba functionality as well as getting all information from the Roomba’s sensors.

It would be nice if the worked on multiple platforms. While I initially started in C, the difficulties in non-programmers getting C code to work on many platforms made me leery of that choice. And C doesn’t provide a consistent GUI framework on multiple systems. It turns out that Java has pretty good serial port functionality now (provided by RXTX), and Processing provides a good cross-platform environment for writing graphical Java programs.

I created a Roomba communication API in Java and a GUI in Processing that shows a top-down iconic view of the Roomba universe. The API is called “RoombaComm” and the GUI is called:

RoombaComm_tst

It provides the following capabilities:

• Detect a Roomba and display Roomba status
• Remotely control the Roomba like a little tank
• Read and display bump, wheeldrop, cliff and dirt sensors
• Display angle and velocity data from the Roomba both numerically and iconically
• Start and stop vacuum on the Roomba
• Play notes on the Roomba using the computer keyboard as a musical keyboard
• Display Roomba button press status

The software is still very rough and not very well structured nor documented. However if you have a Roomba serial interface and want to play with it, it can be downloaded at:

• roombacomm_tst_alpha.zip

Trying it out
In the zip file above, there are executables for Mac OS X, Windows, and Linux. I’ve only tried the OS X one. Give one of them a try and see if it works for you. If not…

To use it inside of Processing:

1. Download and install Processing
2. In the Processing document folder (“Documents/Processing” on Mac or “My Documents/Processing” on PC), unzip the above zipfile. It should create a directory called “roombacomm_tst”
3. Launch Processing and choose File->Sketchbook->roombacomm_tst to open the program
4. Click the Play icon to compile and start the program
5. RoombaComm_tst will then give you a list of serial ports, pick the serial port that you’ve plugged the Roomba in to. On Mac OS X, there are both “/dev/cu.blahblah” and “/dev/tty.blahblah” serial ports. Always choose the “/dev/cu.blahblah” ports. On PCs, it will be whatever COM port number you’ve selected. On my Mac, the Keyspan adapter is “/dev/cu.KeySerial1” and on my PC, the Keyspan adapter is “COM6”.
6. RoombaComm_tst will open that serial port and attempt to talk to the Roomba. If it is not successful, it will display “status: no roomba”.
7. If it’s succesful, drive the Roomba around with the arrow keys, play tunes with the “asdf…” keys and so on!

Here’s what it looks like when just playing around:

Let me know if you try this out and give me feedback on how it works for you.

Update:

First release of RoombaComm API for Java and Processing