DIY prototype RPN/TENKEY programmable calc with printer <:3)--

[macieksoft]

Things are progressing slowly.

Now i finally got the FLASH memory (25q64 on SPI) for storing programs. With current software it allows to store 256 programs on a memory chip, however the memory itself can hold so much more, it is 8 megabytes (64 megabits) one, quite big as for a stupid calc ;-)

Each program have 16 character name (in ASCII), so i can browse them by the name, list of programs written to the FLASH memory appears on right display and can be scrolled by the encoder.

Experimental feature was added to access SPI from calculator's keyboard, so i can send and read anything over SPI (like memory serial number and so).

Sometimes left LCD was showing rubbish, it took me a day to figure out what was causing it. I was thinking that it doesn't like 3V3 logic level, but it was not a case. Turns out that it was LiquidCrystal library that was causing troubles, i increased delay times for some low level LCD commands and the problem is gone. Seems like left LCD probably has slower grade controller chip on it. Or maybe the timing problem is due to the fact that i am using 2 LCDs on same bus, which very few people do (probably library was never tested for such configuration).

Near future plan is bigger display. I mean using FPGA as character generator so i can use VGA display as virtual printer or big display showing whole stack (which is now 9 level), tenkey adders and all that stuff at once.