Letter Clock

As the Serbian language is quite complicated, with "heavy" and long sentences, it needs larger XY alpha matrix. But, there are two unique details - all letters are used (there are no dummy letters), and some words are vertically aligned - like in the crosswords.  GPS receiver L80 is used, so there is no internal timebase, no battery and no adjustment keys. MCU is PIC18F2525. There is the phototransistor which is used to dim LEDs automatically.

Here is the letter arrangement - it was a huge job to solve it, some words (blue characters on the drawing) are aligned vertically, although all letters are used horizontally.