ATOM FPGA

discussion of games, software, hardware & emulators relating to the Acorn Atom
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AlanD
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ATOM FPGA

Post by AlanD » Mon Mar 18, 2013 9:07 pm

Hello All

i got a little side tracked whilst working on my master128 in an FPGA

and i now have a complete ATOM in fpga

spec so far

40K RAM
8255 pia
6255 via
6502
6847 with scan doubled outptut
colour output
sound

i think this is 99% compatible with orignal atom
it plays all the retrosoftware releases
and most of what on the disk images i have

sd card using kees excellent sddos
chuckie3.png
chuckie3.png (449.76 KiB) Viewed 1625 times

AlanD

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oss003
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Re: ATOM FPGA

Post by oss003 » Mon Mar 18, 2013 9:14 pm

WWOOWW .... Alan :shock:

Great job!!!!! =D> =D>

There's still one thing to wish .... the RAM/ROM board.
Especially the ROM banks switchable at #BFFF :)

Greetings
Kees

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jms2
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Re: ATOM FPGA

Post by jms2 » Mon Mar 18, 2013 9:21 pm

Fantastic - well done!! =D> =D>

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TheCorfiot
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Re: ATOM FPGA

Post by TheCorfiot » Mon Mar 18, 2013 9:21 pm

Amazing work...very impressive.

How do we put one of the beauties together my friend.

Having recently repaired an Atom I am feeling the need for one but I would be much happier with an FPGA version..

Regards
TC :)

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danielj
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Re: ATOM FPGA

Post by danielj » Mon Mar 18, 2013 9:23 pm

=D> basically... =D>

Brilliant.

d.

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Re: ATOM FPGA

Post by fatbob_gb » Mon Mar 18, 2013 9:24 pm

They are both things of beauty.

I wish I could be so productive when I get "side tracked"

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AlanD
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Re: ATOM FPGA

Post by AlanD » Mon Mar 18, 2013 9:31 pm

Hello All

i have ordered one of these boards (25 euros pretty good price)

https://www.olimex.com/Products/Modules/Video/MOD-VGA/

when it arrives i will do whats needed to get it up and running
assuming it all goes to plan i will release whatever mods the olimex board needs
along with the vhdl for the atom itself

:D

AlanD

I'm attending ...
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edit

i will bring the fpga ATOM to wakefield for anyone who wants to see

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TheCorfiot
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Re: ATOM FPGA

Post by TheCorfiot » Mon Mar 18, 2013 10:06 pm

That would be fantastic...
Thank you Alan, I will be ordering one soon...

TC =D>
AlanD wrote:Hello All

i have ordered one of these boards (25 euros pretty good price)

https://www.olimex.com/Products/Modules/Video/MOD-VGA/

when it arrives i will do whats needed to get it up and running
assuming it all goes to plan i will release whatever mods the olimex board needs
along with the vhdl for the atom itself

:D

AlanD

I'm attending ...
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edit

i will bring the fpga ATOM to wakefield for anyone who wants to see

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AlanD
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Re: ATOM FPGA

Post by AlanD » Mon Mar 18, 2013 10:20 pm

Hello

@TheCorfiot please wait until i have proven it is a suitable board

i will post as soon as i have mine and have got it working

AlanD

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paulv
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Re: ATOM FPGA

Post by paulv » Mon Mar 18, 2013 10:26 pm

That looks very, very cool indeed.

=D> =D> =D> =D>

I'd certainly be interested in running one too once you've sorted out any issues with the new board :D

Nice work.

Paul

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oss003
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Re: ATOM FPGA

Post by oss003 » Tue Mar 19, 2013 7:28 am

Hi Alan,

for final testing .... the latest Retrosoft disk with joystick support on PORTB of the AtoMMC interface.

Greetings
Kees

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oss003
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Re: ATOM FPGA

Post by oss003 » Tue Mar 19, 2013 1:55 pm

Oops ..... wrong version :oops:

This is the latest including Jungle Journey!

Greetings
Kees
Attachments
RS5-C.zip
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BigEd
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Re: ATOM FPGA

Post by BigEd » Tue Mar 19, 2013 6:32 pm

AlanD wrote:Hello

@TheCorfiot please wait until i have proven it is a suitable board

i will post as soon as i have mine and have got it working

AlanD
Fantastic! Look forward to it.
Cheers
Ed

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Re: ATOM FPGA

Post by Prime » Tue Mar 19, 2013 7:06 pm

That's brilliant Alan,

So at some point we gonna have an FPGA that can boot as any of the Acorn 8 bits ?

Cheers.

Phill.

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Re: ATOM FPGA

Post by thecellartroll » Tue Mar 19, 2013 7:53 pm

Prime wrote:That's brilliant Alan,

So at some point we gonna have an FPGA that can boot as any of the Acorn 8 bits ?

Cheers.

Phill.
Droooooooooool!

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MartinB
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Re: ATOM FPGA

Post by MartinB » Tue Mar 19, 2013 8:04 pm

Very nice indeed Alan Image

Do you get to be this creative at work? You must be a very valuable resource - whatever they pay you, it isn't enough [-( :wink:

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AlanD
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Re: ATOM FPGA

Post by AlanD » Tue Mar 19, 2013 8:45 pm

Hello Phill.
That's brilliant Alan,

So at some point we gonna have an FPGA that can boot as any of the Acorn 8 bits ?

Cheers.

Phill.
@Phill. Thats got to be the ultimate target i guess :D

@MartinB this is just a bit of fun and reasonably straight forward compared to work :D

ATB

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AlanD
Last edited by AlanD on Wed Mar 27, 2013 10:35 pm, edited 1 time in total.

Keith
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Re: ATOM FPGA

Post by Keith » Tue Mar 26, 2013 12:08 pm

Congratulations! I did the Atom in FPGA in 2001, using a WDC 65C02:
http://members.casema.nl/hhaydn/howel/l ... roject.htm
I added many fun features but my spare time has been sold off since December 2005. Since then, analogue tellies and monitors have undergone mass extinction.
I will be getting my evenings back in 6 to 12 months so I'm thinking about what to do getting back in the saddle. To bring my Atom project up to date I can either interface to HDMI/DisplayPort, or directly to a small LCD. I feel the latter makes more sense. The huge demand for mobile computing has made small LCDs very affordable. I bought a replacement LCD for a decent mobile phone for around £10. I think a mobile-phone sized Acorn Atom with a 320x240 (QVGA) or 480x270 (quarter HD screen) would be cooler than something I have to plug into a big telly.
:)

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AlanD
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Re: ATOM FPGA

Post by AlanD » Tue Mar 26, 2013 7:09 pm

Hello Keith

thanks for you interest

i had seen mention of your fpga atom
as you see i have implemented everything in the gate array except SRAM
as it is a fairly simple machine

I eventually aim to have one multi configure board for all my acorn cores

AlanD

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Last edited by AlanD on Wed Mar 27, 2013 10:35 pm, edited 1 time in total.

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jonb
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Re: ATOM FPGA

Post by jonb » Tue Mar 26, 2013 8:57 pm

Hmm, fascinating, I like it!

If only one could find an Atom with irreparable insides that's not getting bid up to silly money on a certain well known auction site.. You could use an FPGA implementation to replace the guts and (let's fantasise for a moment) connect up the still working keyboard part. So you get the full retro Atom experience without emulation but with top video quality...

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hoglet
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Re: ATOM FPGA

Post by hoglet » Tue Mar 26, 2013 10:43 pm

I wonder how long it would take to print an Atom case with a (large) 3D printer?

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retroclinic
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Re: ATOM FPGA

Post by retroclinic » Wed Mar 27, 2013 10:25 am

hoglet wrote:I wonder how long it would take to print an Atom case with a (large) 3D printer?
What would be cool would be to do a perfect mini replica, like 50% or 25% size. Keys would be a trick though.

Mark.
Image

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AlanD
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Re: ATOM FPGA

Post by AlanD » Wed Mar 27, 2013 10:33 pm

I like your train of thought there Mark

perhap sub atomic in size

AlanD

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hoglet
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Re: ATOM FPGA

Post by hoglet » Sun Oct 13, 2013 9:23 pm

(continued from Atom Colour Board Thread)

I think it will take a bit longer than I had hoped to get the Atom Software Archive running on "Atom FPGA", for two reasons:

1. I don't have a SDCARD socket anywhere :(

2. Atom FPGA supports the older SDROM Interface and SDDOS

The problem is, the Atom Software Archive was created with the newer AtomMMC interface in mind. The environment that SDDOS provides is very different, based on individual Disks, rather than a single big FAT filesystem.

The options seem to be:

1. Port Atom Software Archive to SDROM/SDDOS

2. Implement the AtomMMC2 interface - very challenging, because of it's complex PIC device.

3. Plug in the real AtomMMC interface to the FPGA, but this is cheating, and there would be issues with 3.3V/5V IO incompatability.

I'll have a think about the possibility of (1), where each title becomes a separate disk. But this is quite a lot of new work.

Kees, do you have any bright ideas? I want my second Atom to be as useful as my first :lol:

Dave

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Re: ATOM FPGA

Post by Keith » Sun Oct 13, 2013 10:11 pm

I would like to add an SD card interface to my own Atom design, and saw existing designs that used a PIC as a slave doing the bit-bashing. I'm not going to stuff another micro in my packed FPGA so I looked for alternatives, preferably ones with software so I don't have to write it.

I also have 'implement a BBC micro' on my to-do list, and that will have the same requirement. I found and bought this product:
http://www.ebay.co.uk/itm/Acorn-BBC-Mic ... 4aca2507b5

It is much faster than other designs, and I bought it to analyse the circuit so I could implement in my FPGA. I recall it is simple but allows the 6502 to avoid the software burden of much bit reading and writing. It is no problem to use the binary data in a BBC-in-FPGA, but to port it to an Atom design I would have to disassemble the ROM image to see what it was doing. Which in turn means I would need to understand the MMC protocol (which I do not).

Charlie Robson and Kees van Oss have already interfaced the SD card, so they might be able to see how the BBC MMC software and hardware is being clever and know how to take advantage of it.

I could have a go at disassembling the BBC MMC code, but this would do little more than split data from code. There would be no meaningful names to say what is going on, nor comments.

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jonb
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Re: ATOM FPGA

Post by jonb » Mon Oct 14, 2013 8:45 am

Why don't you ask the guy who makes them (I think it's Sprow.. http://www.sprow.co.uk) if he will open-source the code?

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Re: ATOM FPGA

Post by RobC » Mon Oct 14, 2013 8:59 am

Keith wrote:I could have a go at disassembling the BBC MMC code, but this would do little more than split data from code. There would be no meaningful names to say what is going on, nor comments.
The original Beeb MMC design was by Martin Mather and he released the source code for his patches to DFS 0.9. The info has been preserved on this website:
http://swhs.home.xs4all.nl/bbc/mmbeeb/# ... cesoftware

I'm not sure how much the IFEL/ctorwy31 device differs from Martin's original design but it might help to explain the MMC protocol.

Cheers,

Rob

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hoglet
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Re: ATOM FPGA

Post by hoglet » Tue Oct 15, 2013 7:45 pm

I found this snippet from the mmbeeb page interesting:
The associated software (see below) uses the interface to create a serial “SPI” bus to communicate with the MMC card. The clock (PB1) and data out (PB0) are controlled by software, and data in (CB2) is shifted into the 6522’s Shift Register (SRMODE0 - see the Advanced User Guide, page 409).

The read/write speed is approximately 10Kbytes/second.
For reading all the processor will be doing is toggling PB1 up and down 8 times, then reading the byte out of the 6502 shift register.

The read byte code looks like:

Code: Select all

 1550 \ Read byte UP
 1560 .upread \ write FF
 1570 LDX #1
 1580 :
 1590 .upreadX \ X=1
 1600 LDA #3
 1610 STX iorb%:STA iorb%
 1620 :
 1630 .upread7
 1640 STX iorb%:STA iorb%
 1650 STX iorb%:STA iorb%
 1660 STX iorb%:STA iorb%
 1670 .upread4
 1680 STX iorb%:STA iorb%
 1690 STX iorb%:STA iorb%
 1700 STX iorb%:STA iorb%
 1710 STX iorb%:STA iorb%
 1720 :
 1730 LDA sr%
 1740 RTS
The write code seems a bit less efficient, but is quite cunning:

Code: Select all

 1760 .upwrite \ ignore byte in
 1770 ASL A
 1780 ROL A
 1790 STA iorb%
 1800 ORA #2
 1810 STA iorb%
 1820 ]
 1830 FOR x=1 TO 7
 1840 [OPT opt%
 1850 ROL A
 1860 AND #&FD
 1870 STA iorb%
 1880 ORA #2
 1890 STA iorb%
 1900 ]
 1910 NEXT
 1920 [OPT opt%
 1930 RTS
One thing I don't understand is that as well as the 6522 at &FE6x, there is also something at FE18 called mmc.

Dave

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hoglet
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Re: ATOM FPGA

Post by hoglet » Tue Oct 15, 2013 7:56 pm

For reference, the Atom SDROM interface uses PB0, PB5, PB6 and PB7, and consequently I would expect it to be a bit less efficient.

Kees, can you pull the read and write byte code out of SDDOS 2.2 for comparison?

Dave
Last edited by hoglet on Tue Oct 15, 2013 8:23 pm, edited 1 time in total.

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oss003
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Re: ATOM FPGA

Post by oss003 » Tue Oct 15, 2013 8:17 pm

hoglet wrote:For reference, the Atom SDROM interface uses PB0, PB5, PB6 and PB7, and consequently I would expect it to be a bit less efficient.

Kees, can you pull the read and write byte code out of SDROM 2.2 for comparison?

Dave
Hi Dave,

BeebMMC is bitbanging SPI using the VIA but AtoMMC2 communicates with sending commands to the 18F4525 controller and the controller communicates by SPI to the SD-card. So it's not comparable.

AtoMMC1 was connected to the VIA and used bitbanging SPI but AtoMMC is much much faster and more flexible.

Greetings
Kees

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