NP-41 Emulator (may be)

[rprosperi]

(01-28-2016 06:55 PM)Chris Chung Wrote:  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.

Thanks for taking a look at the expandability possibilities; IMHO well worth the time to check so I appreciate it!

2 x 4K ROMs is certainly far better than none, especially since folks can pick their own ROMs. Most of the modern ROMs in use need more than this, since many rely on Angel's LIB4 to be present (thus taking up one ROM already) and they also use bank-switching, again size-prohibitive. But in truth, most folks using these ROMs also most likely will prefer using original 41C h/w.

But it would allow use of the vast majority of the original Application ROMs, both from HP and many 3rd parties, which is probably hundreds of ROMs in total.

Bottom line: Heck Yes, very useful in most cases!!

I don't recall the 41 version you are proposing - 41C, 41CV or 41CX (obviously preferred, but requires a crystal for the clock, etc.)?

We will stay tuned, and thanks for your considerate approach to developing these cool toys Chris!