16c74a

I've been using the Mk1 board for some time with success. Its main role is to act as a sun/cloud sensor - using some light dependent resistors to measure when they're in direct sunlight (and therefore create shadows) or if the day is cloudy (hence no shadows). The non-linear nature of the LDR's light-resistance relationship does mean that when the sun is very bright, there is only a matter of a few counts difference between a sensor in the light (i.e. pointing towards the sun) and one in shade (with it's light sensitive component in shadow).

The hardware is adapted from the Microchip application note: Care and Feeding of the PIC16C74 and its peripherals.The firmware also uses (with adaptations) the example code given in that document.
Here's the code