NP-41 Emulator (may be)

[Chris Chung]

Bob, Sylvian: thanks for the documents and the tip on the memory management. They are very useful for my exploring ROM extension possibilities.

Jean, J-F: seems like I've opened up a can of worms (or candies). I've seen mentions on HP-IL, Pill-Box and other 41 peripheral / extensions quite frequently in the forum, but did not take the time to explore them. So I will have a lot to catch-up to.

The original goal of the slim version is to create a lower cost HP-41 like machine so that I can carry around and play w/ FOCAL programming everywhere, plus I want something my kids can use in class and also a chance for them to explore RPN. And it can appeal to others who've never seen an RPN calculator before.

I am thinking of ways to squeeze the most juice out from the current design.

The 20K or so flash memory left unused can be used into ROM module storage of up to 4 x 4K rom modules (w/ compression 4K 10bit ROM takes 5Kbyte).

There are still 10+ GPIO lines I can used, so SPI, I2C, 2nd UART are all possible. Socket / slot for daughter board type expansion seems like a feasible idea.

The other options is to adopt a more capable MCU, something like 128K+ flash and 8K+ RAM. This will take longer as a lot of stuff need to start again.