NP-41 Emulator (may be)

[Chris Chung]

(01-27-2016 03:44 PM)Thomas_Sch Wrote:  

(01-26-2016 09:49 PM)jch Wrote:  ...
I'm too lazy to check where I saw it, but a recent post stated something like 'one step at a time', and IMHO, NP-41, IS a major step, nice hardware design, 3D printed case & keys, expansion capabilities... Already a very serious calc ground.

I'm excited to get one.
Jean-Christophe

Same for me!
Thomas

After looking into the peripheral and ROM extensions in more detail, I can see the current hardware is not adequate to support them. Anyway, my objective for this design has not change. It should stay being simple and easy to build. Altering the design will take more time than I like, as I need to know the stuffs (ROM / HP-IL, etc) in order to implement them.

I would still like to make provisions for expansion based on the somewhat limited hardware resource. Running ROM instructions from external chips via SPI / I2C will be way slow. So the most I can do is try to use the spare flash memory on the MSP430G2955. I would think there will be always 10k left, enough for a 2 x 4K ROM module.

I am planning to add an micro SD/MMC card reader to the unit w/ a read-only small footprint FAT file system. I can place ROM files in a SD card (up to 2G), and via software setup, I can "load" particular ROM from the FAT FS to a flash partition in the MCU. The loading will take a few seconds and have the effect of inserting a ROM pack into slot 1. And the unit will have only 1 slot, as restricted by the available flash memory.

My question is, will this be useful in many / most cases? As the ROM module space is limited to 2 x 4K.