Intro
A colleague of mine recently asked me if I knew of a small LCD (3-inch-ish) plus touchscreen he could connect to his Raspberry Pi: he wanted to make it into something he could build into his car to play mp3s, take phone calls over bluetooth etc.
Unfortunately, with the Pi, you have only a couple of options: connect a LCD over composite, which won't do the image quality much good; connect it over HDMI, which isn't compatible with many cheap and small LCDs. You can als try to connect it over the DSI interface, but that doesn't have many compatible LCDs or converter boards at this moment. The interface also doesn't seem to be functional in the current RPi software yet.
This made me think: You can get nice 3.2" LCDs with integrated touchscreens for about EUR20 on eBay nowadays. They have an integrated controller, so you don't need to have video hardware in the system you connect it to. Why not hook something like that up to a Linux-based embedded board? I decided this was something worth investigating, so I bought myself a nice 320x240 LCD with an integrated SSD1289 controller. It also has an ADS7846 touch controller for the resistive touch screen.
I wasn't one of the lucky few who had their Raspberry Pi in yet, so I decided to try connecting the LCD to another Linux board: the 8devices Carambola. This board is a cheap and tiny router-derived Linux board, with lots of network connectivity, a 350MHz CPU, 8MB of flash, 32MB of RAM, and important for this project: open-source software (openwrt-based) and some spare GPIOs and an SPI interface. So, let's see if the Carambola can be made to talk to the LCD!1 Next »