RPN scientific calculator firmware for $13 calculator kit

[Maximilian Hohmann]

Hello!

(10-19-2019 12:18 AM)toml_12953 Wrote:  I haven't reflashed my controller yet but wanted to test the build before I do. I have a problem. When I switch modes, sometimes the first character of "Color Ring R C 5" is missing. ...

This behavior is somewhat strage because the display is a standalone unit with it's own controller and should either work OK or not work at all... The display contents are transmitted from the microcontroller through an 8-bit data bus and some handshake signals. Therefore the first character, which your display is missing sometimes, should be in no was different to all the othes. So I would suspect a fault inside the display itself. Or some weird timing problem which causes the handshake between controller and display to occasionally lose the first character. There is not much that can be done there because the controller generates it's clock internally as it looks from the schematics.

I can not see this fault on my calculator (I have bought two but assembled only one).

(10-19-2019 12:18 AM)toml_12953 Wrote:  Also, where to I connect to the board to reflash the chip?

The instructions including the connection that needs to be made are here: https://github.com/jjj11x/stc_rpncalc

On my calculator the processor is not soldered into the board but plugged into a socket. I can't remember if that socket was supllied with the kit or if I added it myself. If yours also has a socket you can remove it from the board and flash it externally on a breadboard, therefore avoiding to have to solder anything to the processor pins directly (as on the github site).

Regards
Max

NB: Myself I have not tried to reflash one of these units because all the software required for it only runs on Windows computers.