Saturday, June 18, 2011
Keypad Controller Demo Video & Walk-through
Demo: Power-on the phone, then wait to boot. Next, dial 0-1-2-3-4-5-6-7-8-9-#-* then key down, down, down, down, up, down, OK, wait a couple of seconds, then cancel. Repeat dial sequence two more times. Then power key again to turn it off. Then a quick tour of the hardware...
Tour of the hardware: The phone is an LG "Flare" (LX165) from Virgin Mobile. There are 24 keypad buttons on this phone. The phone is wired with two Cat5 wire bundles because I had some handy and I like the easily identified wires all nicely bundled together. However, instead of using 48 wires and 24 relays to control the 24 buttons, I use only 14 wires. These wires are soldered to specific phone keypad conductors that I determined to make up the "rows" and "columns" of the keypad matrix. I connected these wires to a cross-point switch circuit on my board. For the cross-point switch, I am using 6 Vishay ILQ2 quad opto-coupler ICs instead of relays. When compared to relays, like the OMR-C-105H used for the power control, the opto-couplers are more compact and cost about half as much per switch. To control the opto-couplers I am using three 74HC138A ICs which are 3-to-8 bit decoders with complementary outputs. From the decoders there are 6 wires to the Arduino UNO board.
I have posted schematics for the board design. Click the "Appendix" tab (above).
The real trick to the entire hack is reverse-engineering the phone's keypad. I will publish a separate post on that topic later.
For the most part, I think the hardware to control the phone finished. Now I have a bunch of software to write. To start, I am going to work on composing text messages. To do this, I'm going to figure out how to interactively control the phone thru my PC or some other means. I am thinking of reverse-engineering an IR remote control for this. I know. It is more than a little ironic. But, since the phone's keypad is now useless, I can no longer use it to play around with the phone and figure out how to navigate through the menus and compose text messages. This will be much faster if I can do it interactively.
Posted by j8g8j