Page 90 - Hacking Roomba

Chapter 4 — Building a Roomba Bluetooth Interface 71

There are many other Bluetooth serial adapters, some meant for hacker use like the BlueSMiRF
and some with normal RS-232 ports for wirelessly connecting existing serial devices. In the lat-
ter category are devices like the IOGear GBS301, which looks eminently hackable and was
going to be the core of this project if the BlueSMiRF hadn’t come along. In the former cate-
gory is the blu2i module available from Tek Gear. It looks a lot like the BlueSMiRF but is
almost twice the price.

The circuit presented here is just one of many ways of adding Bluetooth to the Roomba. The
above devices could be used instead. If you have easy access to one of them, try playing around
with it. If you have more than one, try adding Bluetooth to something else in addition to
Roomba, like your coffee maker or stereo. These little wireless communication gadgets are fun to
hack on to a variety of things.

The BlueSMiRF module is sensitive to static electricity. Make sure you’re properly grounded
before handling it. See Appendix A for techniques for staying grounded.

Building the Bluetooth Adapter

Construction of this circuit will be a good deal easier than the serial tether because of the lower
part count. The BlueSMiRF does all the hard work.
It’s easy to burn yourself with a soldering iron. Be careful, always know where it’s at, and always
make sure to turn it off when done. Also be sure to be properly grounded so you don’t zap
anything.

Getting the Parts Together

Figure 4-4 shows the parts needed for this project. The Mini DIN cable connector is shown at
the top. Right below it is a horizontal rectangle that is the BlueSMiRF Bluetooth module.
The circuit board below that is the one you’ve seen in Chapter 3. The two 1 µF capacitors are
at the left bottom. For this particular version of the Bluetooth adapter, two matching capacitors
couldn’t be found in the junk box, so a mismatched set was used. Next to that is the three-legged
78L05 voltage regulator. And on the bottom right is the resistor and LED for the power on
light. The little black square to the right of the circuit board is the header receptacle that the
BlueSMiRF will plug in to. It’s safer to solder a receptacle down than to solder directly to the
somewhat sensitive BlueSMiRF.