### DESCRIPTION

This PCB allow to build my own calculator, some different like you may buy in stores (Casio etc).

### TECHNICAL DETAILS / COMPONENTS

Main set components on PCB is ATMEGA128A, static ram memory - AS6C1008-55 (128kB), flash memory AT45DB328 and FT232R. uC controls moreover 128x64 lcd and resistive touch panel.

My idea was build calculator with touch screen and get a lot of cells where i may places formulas or texts, like a real excell. Static ram memory stores all this entered data and you may save this sheet in flash memory. SRAM data bus is common with LCD data bus, control lines are separate so it is possible to load LCD data from SRAM without copy its to uC. If send one byte requires 18 uC tacts it is possible to reach even 500kB/s data transfer.

For calculate formulas i use revers polish notatnion alghoritm (with change notation form infix to postfix). This code allow to write clear formulas and is easy to maintain.

FT232R allow communication with PC via USB virtual port com. Device have two NiMH accumulators, Attiny25 is charge controller.

I have myself developed a way to control the touch panel using adc, with no external touch controller. I did not implement shifting because I found this unnecessary at this stage.

The source code is quite old, my skills have also evolved a bit so I will probably start writing it again.

### LEARN / TOPIC / BUILD INSTRUCTIONS