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Forum Index : Microcontroller and PC projects : Something else

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knivd

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Joined: 07/09/2014
Location: United Kingdom
Posts: 23
Posted: 08:48am 26 Feb 2021
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Here is a project I've been fiddling with for the past few months.
It is inspired by the early MM but runs C :)

http://ello.cc
 
Rado
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Joined: 27/11/2020
Location: Croatia
Posts: 31
Posted: 09:49am 26 Feb 2021
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That looks nice. I think that in the documentation, where you put "premium":

"While there is an execution speed premium to this, a benefit is the possibility to run sources directly from a read-only memory."

you actually meant "penalty"?

(also, I can't see PS/2 connector in the picture?)
 
knivd

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Joined: 07/09/2014
Location: United Kingdom
Posts: 23
Posted: 09:59am 26 Feb 2021
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  Rado said  That looks nice. I think that in the documentation, where you put "premium":

"While there is an execution speed premium to this, a benefit is the possibility to run sources directly from a read-only memory."

you actually meant "penalty"?

(also, I can't see PS/2 connector in the picture?)


Yes, a typo, or whatever it is called when you use the wrong word... I will fix that.
Here is the PS/2 too


 
matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 4738
Posted: 10:27am 26 Feb 2021
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Very neat  

Couple of minor issues on the schematic. You are being a bit unkind on any VGA monitor by not clamping the RGB outputs to 0.7V. Also, dual mode USB/PS2 keyboards and mice seem to set their mode based on the presence or absence of pullups on the clock and data lines. Whereas PS2 only devices will work with the schematic as drawn we have found on the CMM2 that 4K7 pullups are essential for dual mode mice to work in PS2 mode and I assume the issue will be the same for dual mode keyboards
 
zeitfest
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Joined: 31/07/2019
Location: Australia
Posts: 181
Posted: 10:28am 26 Feb 2021
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includes a tiny C interpreter

now thats tricky.
Edited 2021-02-26 20:30 by zeitfest
 
knivd

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Joined: 07/09/2014
Location: United Kingdom
Posts: 23
Posted: 11:25am 26 Feb 2021
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  matherp said  Very neat  

Couple of minor issues on the schematic. You are being a bit unkind on any VGA monitor by not clamping the RGB outputs to 0.7V. Also, dual mode USB/PS2 keyboards and mice seem to set their mode based on the presence or absence of pullups on the clock and data lines. Whereas PS2 only devices will work with the schematic as drawn we have found on the CMM2 that 4K7 pullups are essential for dual mode mice to work in PS2 mode and I assume the issue will be the same for dual mode keyboards



Thanks!
Yes, I am aware of those things. My goal was to build the absolute barebone system, making some assumptions on the way, of course. Using the internal pullups. I have tested with a few keyboards and monitors that I have and they all worked. Surely there might be some others that won't be happy, but it is a trade off for simplicity. Support for mouse I think is a bit pointless in a 64K mono machine.

PS. I have some leftover boards from the previous revision. For free, I will only want the P&P. Always feeling bad if I need to throw away perfectly good PCBs.
The only difference between the previous version and the current release is that it uses MCP1700-3302 which is a lower current LDO than the one in the current board.
Edited 2021-02-26 22:38 by knivd
 
MauroXavier
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Joined: 06/03/2016
Location: Brazil
Posts: 273
Posted: 12:56pm 26 Feb 2021
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What fantastic work!

Someday I will put my "dirty" hands on it to make games...

  knivd said  Support for mouse I think is a bit pointless in a 64K mono machine.

Don't say that... I believe it's possible to develop a Missile Command clone for this wonderful little machine. Mono isn't a problem at all, as you created great native line patterns.
Edited 2021-02-26 22:56 by MauroXavier
 
lizby
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Joined: 17/05/2016
Location: United States
Posts: 1264
Posted: 01:00pm 26 Feb 2021
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Very neat indeed. A better subject line might have given more clues and drawn more attention, something like:

ELLO Computer with VGA and Small C Interpreter

The C interpreter is, to my mind, a major accomplishment--a fuller implementation than my first C compiler--Ron Cain's Small C from the May 1980 issue of Dr. Dobb's Journal of Computer Calisthenics & Orthodontia.

Kudos. Nice web site, too.

I would indeed be interested in a board, and have PMed you.
 
Swartz
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Joined: 15/12/2020
Location: United States
Posts: 15
Posted: 04:10pm 26 Feb 2021
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knivd -

This is a really neat project! It will be great fun to track it. When you declare it "ready for general release" I will grab up a couple to play around with. In the past I had written a C-like language interpreter but certainly *nothing that would embeddable* . Congratulations!

Swartz
 
Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 123
Posted: 04:27pm 26 Feb 2021
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What a lovely little thing!
I know sod all C though. lol
-- Mick

Zilog Inside! nascom.info for Nascom & Gemini
 
mclout999
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Joined: 05/07/2020
Location: United States
Posts: 294
Posted: 05:12pm 26 Feb 2021
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It is like a simplified CMM1 mono with C?  Is that a good approximation? Not a lot of GPIO available and what kind of Expansion is planned or possible?
 
lizby
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Joined: 17/05/2016
Location: United States
Posts: 1264
Posted: 06:11pm 26 Feb 2021
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  matherp said   . . . You are being a bit unkind on any VGA monitor by not clamping the RGB outputs to 0.7V.


What additional circuitry would be required to achieve the suggested protection?
 
matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 4738
Posted: 06:17pm 26 Feb 2021
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  Quote  What additional circuitry would be required to achieve the suggested protection?

Inline resistor into a diode - see the CMM1 circuit on Geoff's site
 
knivd

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Joined: 07/09/2014
Location: United Kingdom
Posts: 23
Posted: 06:24pm 26 Feb 2021
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  mclout999 said  It is like a simplified CMM1 mono with C?  Is that a good approximation? Not a lot of GPIO available and what kind of Expansion is planned or possible?


Yes, that is a close approximation. The lack of GPIO really comes from the MCU package. That PIC32 is currently the most powerful through-hole MCU on the market.
In terms of expansion, I am yet to complete the <platform.h> library with functions for I/O and comms.
Then, the first expansions could be an RTC clock (the expansion header is already compatible with one such popular option on Aliexpress), and maybe a serial RAM expansion.
 
knivd

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Joined: 07/09/2014
Location: United Kingdom
Posts: 23
Posted: 06:53pm 26 Feb 2021
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  matherp said  
  Quote  What additional circuitry would be required to achieve the suggested protection?

Inline resistor into a diode - see the CMM1 circuit on Geoff's site


Yes, that would be the correct one. I even had it in the earliest board, but then discovered that the three monitors I have for testing all have their own internal protection and apparently that is a common thing, so the schematic became two components lighter. It is of course very easy to add them back but it would be mostly to deal with some corner cases.
 
zeitfest
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Joined: 31/07/2019
Location: Australia
Posts: 181
Posted: 11:41am 03 Mar 2021
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Is there an ascii serial i/o , ie instead of using the keyboard and vga ?
 
knivd

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Location: United Kingdom
Posts: 23
Posted: 03:53pm 03 Mar 2021
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  zeitfest said  Is there an ascii serial i/o , ie instead of using the keyboard and vga ?


Not yet implemented. It is quite easy but low on my list of tasks because that invalidates the main point of the board
 
Frank N. Furter
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Joined: 28/05/2012
Location: Germany
Posts: 531
Posted: 07:55am 04 Mar 2021
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Hi Kon,

I just read about your great project - do you have a PCB left?

THANKS!

Frank
 
knivd

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Joined: 07/09/2014
Location: United Kingdom
Posts: 23
Posted: 04:12pm 04 Mar 2021
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  Frank N. Furter said  Hi Kon,

I just read about your great project - do you have a PCB left?

THANKS!

Frank



PM me to discuss.
 
zeitfest
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Joined: 31/07/2019
Location: Australia
Posts: 181
Posted: 01:29pm 06 Mar 2021
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  knivd said  
  zeitfest said  Is there an ascii serial i/o , ie instead of using the keyboard and vga ?


Not yet implemented. It is quite easy but low on my list of tasks because that invalidates the main point of the board



I know it is not your aim, however I would encourage you to make your C interpreter available via a serial i/o...maybe squeeze a mcp2221a on the board, or make it run on the  serial i/o-based boards available. I think there is a lot of demand for it,  a small embedded C board that did not need compiling would be very useful I think, and using a PC for the writing bypasses editors displays etc and makes it cheaper.
 
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