ATtiny Graphical Analog Clock

This analog-style clock by David Johnson-Davies is shown on a 240x240 color TFT display. Impressively, it’s controlled by a mere ATtiny814 chip, along with an external 32.768kHz oscillator to help keep accurate time.

Redrawing an entire 240x240 pixel display every second would likely be a challenge for this type of low-power chip. Instead the project only redraws the second/minute/hour hand as needed, as well as the new blank spots left by the hands’ absence. What’s interesting here is that this type of procedure would normally mean keeping a copy of the display in RAM; however, as explained in more detail in this separate post, the program is actually reading pixel states from the display itself. From this pixel data, the processor can make a decision as to whether or not to update certain parts of the display.

Hardware-wise it’s a fairly straightforward build, and the underlying code can be used with a 240x240 display or several other lower-resolution options including a 128x128 pixel device. A few capacitors and a resistor round out the build, making it easily breadboardable, or you could also use Johnson-Davies' Universal TFT Display Backpack for something a bit more permanent.

It’s a neat usage for sure, and perhaps the most intriguing part about this is the revelation that you can actually read from many such displays. This opens up a wide range of hacking and visualization possibilities that hopefully Johnson-Davies and/or others will pursue to an even greater extent in the future!