I've started work on the led dial. So far I've left it to the users to decide if they want to use i2c or any other way of inter-ic communication, all data transmission pins are available as pin outs.
I've also added a mikroelektronika-compatible programming interface to enable programming of the chip after soldering.
The chosen mcu, pic18F2431, contains both a quadrature decoder and an internal ocillator, making the number of external components very low.
I have not yet tried the programming circuit like this, so it may have to be changed.
The PCB. Dimensions 29 x 29 mm:
I still have some work to do on the footprint of the encoder, and of course have to find a way to solder this since the mcu, resistors and capacitor are SMDs