Re: [f-cpu] Really cheap FCore prototyping...

[Yann Guidon <whygee@xxxxxxxxx>]

hi !

Nikolay Dimitrov wrote:

> Dear all,
>
> Several days I was thinking about the YG thoughts (as I recalled) "... 
> it doesn't matter how fast it is, it does matter that it is free...", 
> I found an interesting solution.
> There are several software simulators for the FCore, but what do you 
> say for a real HARDWARE simulator? No, don't scream, I don't mean 
> FPGA. It's not (very) cheap, and tools are complicated.

well, if it's only a matter of HW, then it's not a big problem :
you probably know that i have now this "machine" !
http://whygee.club.fr/ikos/index.html

now, it's a BIG SW problem and it will need tons and months of 
reverse-engineering
to make it work (before it can be useful for anything).

> But how can one deploy the core on a hardware, without millions of 
> dollars, or even a FPGA? There is a very cheap programmable logic, all 
> around the world, called microcontrollers. PIC, AVR, Atmel ARM7, just 
> name a cheap and fast RISC! 

I have some PICs and use them for many projects, sure,
this could be an interesting approach. Not ultra-fast, but
practical, at least for me and some others.

> To the chip can be connected some SRAM memory to extend the data 
> storage of smaller controllers to hold enough "registers" of the 
> emulated core. I recall - it won't be fast, but this is unique way to 
> CREATE NOW working prototypes of our favourite core!

and the technology is cheap, easy and available. really weird, but a 
great idea :-)

> Just imagine - portable prototypes of FCpu hanging in your pocket, 
> working with a 3V LiIon batt, drawing about 5-15mA, and achieving 0.1 
> - 1 MIPS ?

hmm there, you dream a bit too much ;-)
The way i see it, the FC0 would require some tens of various PICs,
SRAM chips here and there, many TTL-like circuits, and other stuffs.
For a proto, power consumption is not a concern, but it would certainly
draw less than the 3KW of the Ikos machine :-P

> Is this possible? Is the freedom just a MCU ahead :) ? 

i was wondering if i could implement the VSP
http://f-cpu.seul.org/whygee/VSP/
using TTL, old SRAM, some EPROMs (for multiply and other stuffs)
and some PALs, one one or a few boards, in order to run at 1MHz.

Using PICs (or even ADi DSP ! i have many of them but don't use them),
i could solve some of the problems that the TTL-style creates.

For FC0, it would need maybe a dozen of PICs, with the asm carefully tuned
for specific tasks. Reprogrammability is a great benefit during development.
But this won't be enough. Specific discrete logic is needed for many 
other parts anyway,
particularly because the F-CPU uses large words (64 bits and more !).

> P.S.: I almost falled from the chair dreaming... :)

next time, prepare cushions :-)

OK, before the list heats up again,
i prefer to test things on the VSP first.
i had started to make a JAVASCRIPT simulator
http://f-cpu.seul.org/whygee/VSP/vspsim.html
but it's very still far from useful (except for pushing the browser to 
its limits).
The VSP is really simpler, so faster to implement.

Then the FC0 will be a matter of scaling things up :-)

> Best wishes to everyone!

thanks for the mail,

> Nikolay Dimitrov, a.k.a. PicMaster

> Software Developer

YG, yg

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