NP-41 Emulator (may be)

[Chris Chung]

(01-28-2016 08:26 PM)rprosperi Wrote:  I don't recall the 41 version you are proposing - 41C, 41CV or 41CX (obviously preferred, but requires a crystal for the clock, etc.)?

Bob, I am currently running the 41CV ROM that comes w/ nonpareil, there is also a 41CX ROM that I have not try yet. As I understand that it has RTC. I haven't install clock crystal on the NP41S (I will called this design NP41S to differentiate it w/ the 14 segment 128K FRAM unit) but plan to make that available and try the CX ROM.

jch Wrote:

(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.

Are you thinking of GPIO / SPI / UART / ... ?

Jean, for this "value" MCU, there is only one hardware UART + one hardware SPI / I2C.
The UART is used currently used for debugging and will be used to load user domain programs in the future. User will need to purchase a USB-Serial cable to make this work.
A SPI peripheral is used to driBve the DOGM display and will also be used to read SD card.
I am reducing the GPIO for keyboard scanning from 8+5 pins to 10 pins. These will leave about 10 pins for other purpose. I need to put in a buzzer for the BEEP instruction, 2 led back-light pins for the LCD.

The main inadequacy I feel is the lack of flash and RAM. Without on-chip memory there is no way to emulate all 4 slots.

jch Wrote:

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

Or not... If the access time of external devices is low compared to the microinstructions emulation time ?

I would definitely give it a try (it would be fun to do). But as a MCU design, there is no memory bus and I have to use SPI / I2C (serial operation) for fetching individual instructions. And it will take many machine cycles to just fetch a few bytes. You are correct that since the CPU is simulated also, it may not look too bad. Some kind of caching might work to some extend. This is something interesting to try once I got the basic stuff going. Another problem is I only have one hardware SPI to share between LCD and SD card and / or external memory, will have to implement some kind of traffic control or to bit-bang one of the channels.

jch Wrote:

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

I'm affraid that even the small footprint FAT file system will take some precious Flash and RAM ressources.
Perhaps a mix with USB transfer, on board fast serial flash and SD Card ?

Yes, I will be careful here. I will be using a read-only version of the elm-chan petite fat library which is known for low resource draws. With reserving 10K bytes ROM module, I still have 10K code space to play around, so I should be fine. I am just placing the component on the new PCB design. The firmware coding for this part is not my priority.

(01-28-2016 09:51 PM)Thomas_Sch Wrote:  Dear Chris,
Your project should not be the "jack of all trades", at least not in the first step.
Making/offering some (or many) of your basic NP-41 would IMHO satisfy a lot of us.
What if your checks show that the hardware is not suitable? Will there than be no NP-41? An impossible idea ;-)

Thomas, I am moving ahead w/ my original plan regardless. I am trying to adjust the PCB so that these may be improvements can be made afterwards by firmware change. There will be an SD card mount, whether it will be used or not. There will also be a pin socket for possible SPI devices, however enabling it in firmware will not happen immediately.

I am eager to get a physical unit to carry around, with the option of changing and improving the firmware at will.
I am actually carrying the prototype unit everyday and making firmware improvements on it.
I hope the next PCB and firmware work will make it stable enough so that I can offer it to a few early adaptors, which should have means to load firmware (i..e a $10 TI LaunchPad G2) as there will be bugs and enhancements.