While e-paper is common among e-readers, there are very few, if any phones other than the MOTOFONE that exclusively use an e-paper display. [Steve] had one of these phones sitting around and thought it could be used to build a low-power clock. Since the bistable e-paper display can retain the currently active content even when power is removed, he would only need to update the clock once a minute, when the time changed.
Unfortunately for him, very little publicly-available documentation exists for the display controller Motorola used. To get an idea of how the display was driven, he had to sniff the SPI communications between the processor and the display. Once he had the basic commands down, he spent quite a bit of time figuring out how to activate the different segments of the display, due to what seems to be a rushed design process on Motorola’s part.
Now that [Steve] had reverse-engineered just about everything, he connected the phone to a TI MSP430 to drive the display. He programmed the LaunchPad to serve as a basic clock with great results, as you can see in the video below.
If your interest in e-paper hacking has been piqued, be sure to check out our previous e-paper coverage here.