TELEPHONY
time. After closing the connectors down onto the
ribbon cable, it’s a good idea to test for connectivity
and short circuits using a multimeter and a needle.
As a final step, fire up the Chumby and test the
Chumbilical to make sure all functions still work.
The Chumby’s speakers fit nicely at each end of
the handset (Figure G). I wired them to the RJ14
jack on the bottom of the handset, and stuffed
cotton around each speaker to prevent them from
rattling against the plastic.
Remove the Speakers Mount the Control Panel Switch
and Daughtercard The final step was to replace the control panel
Once the Chumbilical worked, I set forth dissecting switch, the squeeze switch at the top of the
the rear assembly of the Chumby. The daughtercard Chumby. The original part is a limit switch with a
is only a few centimeters across and is affixed to the long, curved arm. It fits well within the Chumby, but
rear assembly with several screws. its large, exposed contacts would be easy to short-
The control panel button, 9V battery connector, circuit, making it not very good for other projects.
and speaker wires are attached to the daughterboard The good news is that it’s simple to replace
with plastic connectors and headers, so I gently pulled with any other type of intermittent contact switch.
them off; no desoldering necessary. Disconnecting Initially, I wanted to set up my Chumby so the control
these made the daughtercard slide easily out of the panel switch would be triggered by the rocker that
plastic assembly. rotated when the phone was lifted from the hook.
I measured the space on the daughtercard dedi- But my engineering skill failed me on this, forcing me
cated to the Chumby’s ports, and cut a matching to concede to a standard panel-mount pushbutton
hole in the back of the phone around its original RJ14 drilled in behind the handset cradle. Soldering the
jack. Then I used mounting tape to affix the daugh- wires was easy, but now I have to disconnect that
tercard to the inside of the phone case, with its ports button whenever I open the phone chassis.
and jacks facing out the hole.
The metal baseplate of the phone curves up around
its perimeter, and its back edge covered the Chumby’s
recessed power button, located at the bottom of its
daughter card. I cut a notch in the metal to allow access to the button (Figure F, previous page). This lets
you turn its power off and on with a pen or other small
pointed object, which is the way you’d do it anyway;
the Chumby is meant to be left on continuously.
Future Improvements
While it’s not perfect, it is fun to have a big, retro,
important-looking red phone that happens to run
Linux, tune internet radio, and display widgets
(Figure H). Since the Chumby’s schematics and
source code are all available, all 3 of the following
improvements should be relatively easy work.
Move the Speakers to
the Phone Headset
Using a small screwdriver, I easily broke the brittle
adhesive that attached the Chumby’s speakers
to the rear assembly. To put them in the phone’s
handset, I simply soldered some extension wires
insulated with heat-shrink tubing to the RJ14 jacks
at each end of the existing coiled phone cable. The
cable has 4 wires, so it can drive 2 speakers.
The Chumby’s speaker wires are thick and easy
to strip and solder, making them a good choice for
hacking. Remembering to maintain the polarity,
I soldered the pin connectors on the daughtercard
for the speakers to the RJ14 jack contacts for the
coil cable at the phone end. Then I unscrewed the
microphone and speaker ends of the handset and
simply lifted the 2 disk-shaped components out.
» Build an iPod dock into the back of the unit.
Chumby can read from a USB-connected iPod (but
not iPhone or iPod Touch), and it has a nice touchscreen interface for playing through the speakers.
» Improve access to the power button — likely by
splicing out the Chumbilical’s leads for that contact.
» Connect a switch and hack software to activate
the phone’s “hook” buttons. I eventually want the
device to launch the internet radio application when
you take the handset off the hook. Then, imagine
hanging up the red phone and having internet radio
automatically turn off. Sweet!
Daniel Gentleman (
dan@thoughtfix.com), better known as
ThoughtFix, operates two blogs about mobile technology
and portable Linux devices.
160 Make: Volume
16
