The project was originally inspired by a friend wanting to make a "sexting themed" costume, with a scrolling LED display of live texts sent from people at the party. We found a $13 LED belt buckle online, which looked cool, but only had a few buttons to manually enter in messages. A couple wires and lines of arduino code later, we were able to automate entry of messages.
We then added a host shield and wrote a small Android app to send txt messages on to the arduino.
Step 1: Required Parts and Code
--Android Phone (2.3.3+)
--Scrolling LED Belt Buckle ($13 at writing!)
--USB Host Shield (SparkFun one used here)
--Microbridge Arduino Host Shield to Android Library (Adb)
--Demo arduino code for writing to the LED display and receiving SMS text messages via the USB connection, and Eclipse android project to pass SMS messages to arduino.
Step 2: Automate Message Entry on LED Display
The three push button switches simply short the bottom side of the switch to ground when pressed. We're going to simulate this action by switching the bottom side of the swtich between a high impedance pin (a digital input) and ground (a low digital out). This is easily done by switching the direction of the pin on an arduino, using pinMode(pin, INPUT) or pinMode(pin, OUTPUT). Just make sure the output is set Low before setting the pin to output (digitalWrite(pin,0)).
Four wires are attached, three for the switches, one for ground.