HP-29C ACT compatibility

[Paul Dale]

Bernhard, thanks for the explanation, I understand the difficulties involved and an hardware update would be beyond my skills.

Blanking the display during card reading and printing would be reasonable as a way to avoid different brightness LEDs. It seems like 180kHz is just a little too fast for the processor -- 6 instuctions times 180k is approaching the speed of the CPU. That's not a lot to achieve something useful with. It might be possible to buffer the outputs and then push them in a tight loop.

Is there a suitable PIC that could be used instead? E.g. the 16F18856 comes in the same package and it provides an extra SPI port. The pin outs are different enough it wouldn't just drop in. There are a lot of PIC processors available and something might come closer.


Pauli