As the Serbian language is quite complicated, with "heavy" and
long sentences, it needs larger X×Y 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
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.