"Arcflash" A3000/A3xx/A4xx/A5xx/A5000 in-system programmable ROM -- any interest?

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Fri Dec 07, 2018 4:19 pm

IanS wrote:
Wed Dec 05, 2018 7:40 pm
Could you add some pins to the top end of ROM 4 (e.g. Pins 1-4), just for mechanical support, as the usb connector will be near there?
Updated images (and design files) are up at https://github.com/google/myelin-acorn- ... m_emulator -- see anything else obviously missing? I've labelled the pins to connect to A21/A20/A19/A18/RESET up top, and I've added more pins for mechanical stability around the USB port.
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Re: A3000 in-system programmable ROM -- any interest?

Post by IanS » Fri Dec 07, 2018 4:45 pm

myelin wrote:
Fri Dec 07, 2018 4:19 pm
IanS wrote:
Wed Dec 05, 2018 7:40 pm
Could you add some pins to the top end of ROM 4 (e.g. Pins 1-4), just for mechanical support, as the usb connector will be near there?
Updated images (and design files) are up at https://github.com/google/myelin-acorn- ... m_emulator -- see anything else obviously missing? I've labelled the pins to connect to A21/A20/A19/A18/RESET up top, and I've added more pins for mechanical stability around the USB port.
For A3xx the A18/A19/A20 inputs would ideally be at the other end of the board, but I guess that interferes with the USB stuff. A small extension cable can be made up if needed. The usual connections on the A3xx are from IC28 to the side nearest to ROM4.

Other than that it looks amazing, I hadn't expected to see BGA parts, are the BGA versions of the chips easier to source? Reduces the chance of a DIY build.

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Fri Dec 07, 2018 5:03 pm

Interesting. I’ll take a look and see if maybe I can add a second row of headers for those address signals.

The BGA parts are an interesting tradeoff. They’re easier for me to assemble than hundreds of 0.5mm pitch TQFP pins (wider pitch and easier reflow) but less easily sourced and harder for others to build. Way easier to fit onto the board, however...it would have been even more cramped on there with a QFP CPLD! After routing it all I’m less sure; the BGA signals were a lot of work. But here we are :)
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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Thu Dec 13, 2018 6:33 am

IanS wrote:
Fri Dec 07, 2018 4:45 pm
For A3xx the A18/A19/A20 inputs would ideally be at the other end of the board, but I guess that interferes with the USB stuff. A small extension cable can be made up if needed. The usual connections on the A3xx are from IC28 to the side nearest to ROM4.
Success! I managed to add a second set of connectors for those four signals, at the edge of ROM3, so not quite as far down as the Acorn/IFEL carrier boards, but a bit nearer than the connector up by ROM1.

I've updated the design files and renders at https://github.com/google/myelin-acorn- ... m_emulator
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Re: A3000 in-system programmable ROM -- any interest?

Post by sirbod » Sat Dec 15, 2018 10:20 am

myelin wrote:
Fri Nov 16, 2018 9:56 pm
- MAYBE (I still have to confirm this) the ability to make 4MB of flash visible to the machine by wiring in the A21 line, so you can fit more stuff in your RISC OS build
One of the issues holding back RISC OS 3.20 was the fact I couldn't fit everything into the current ROM size, so supporting a 4MB ROM would be useful.

I'd certainly be interested in some of these boards if 4MB is a thing, as I could then start testing 3.20 on physical to sort out the network stack.

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Sat Dec 15, 2018 10:12 pm

sirbod wrote:
Sat Dec 15, 2018 10:20 am
myelin wrote:
Fri Nov 16, 2018 9:56 pm
- MAYBE (I still have to confirm this) the ability to make 4MB of flash visible to the machine by wiring in the A21 line, so you can fit more stuff in your RISC OS build
One of the issues holding back RISC OS 3.20 was the fact I couldn't fit everything into the current ROM size, so supporting a 4MB ROM would be useful.

I'd certainly be interested in some of these boards if 4MB is a thing, as I could then start testing 3.20 on physical to sort out the network stack.
I’ve wired in that line, so yes, these boards will be 4MB compatible if you solder in the extra connection :)
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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Tue Jan 01, 2019 12:16 am

First board soldered! Reflowed it with Chip-Quik 67/33 solder paste; first time I've used this one, and it seemed to work very well. There were two shorts, both in the fine pitch USB pins. The 0.8mm QFP soldered perfectly, so with any luck the 0.8mm BGA will also have turned out well.

Getting started on firmware now...
2018-12-30-first-board.jpg
Last edited by myelin on Tue Jan 01, 2019 12:18 am, edited 1 time in total.
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Re: A3000 in-system programmable ROM -- any interest?

Post by sirbod » Tue Jan 01, 2019 9:19 am

Impressive stuff. I assume you're using a template for the BGA solder application?

I guess I should put my name down for at lease one to start with, for the A305 I think. Ultimately, if I can get RISC OS 3.2 up and running I'd be looking to upgrade my A305, A440/1, A4000 and A5000. I'll probably leave the A310 as stock so I have a baseline RISC OS 2 machine for legacy games testing.
Last edited by sirbod on Tue Jan 01, 2019 9:46 am, edited 1 time in total.

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Wed Jan 02, 2019 2:48 am

sirbod wrote:
Tue Jan 01, 2019 9:19 am
Impressive stuff. I assume you're using a template for the BGA solder application?
That's right... a lovely laser-cut steel stencil from JLCPCB. I didn't take a picture, but the solder paste deposition was really clean; there was a neat little pile on each of the BGA pads, and nothing in between.
sirbod wrote:
Tue Jan 01, 2019 9:19 am
I guess I should put my name down for at lease one to start with, for the A305 I think. Ultimately, if I can get RISC OS 3.2 up and running I'd be looking to upgrade my A305, A440/1, A4000 and A5000. I'll probably leave the A310 as stock so I have a baseline RISC OS 2 machine for legacy games testing.
Sounds good; I've added you to the list up top :)

Project update: the MCU works, and can scan the JTAG chain (which means the CPLD is probably soldered correctly). Time to write some Verilog so I can program the flash!
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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Wed Jan 02, 2019 5:28 am

I was just taking a look at the A4000 and A5000 schematics and was surprised to see that LA21 is connected up on both -- so both of those machines are already capable of taking a 4MB OS image without needing anything soldered in there.

I have an idea for how to build a board that'll fit over the two ROM sockets -- even more BGA parts than the current one, but I think I can do it.
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Re: A3000 in-system programmable ROM -- any interest?

Post by Joka80 » Thu Jan 03, 2019 3:39 pm

Hello

I have an A3000. The spacing of the ROM sockets on the A3000 and A5000 is different as everybody on this thread has described.

Can you manufacture a board which will plug directly into the A3000 motherboard ROM sockets but then has the A5000 ROM 'spacing' on top?
:D

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Thu Jan 03, 2019 4:19 pm

Joka80 wrote:
Thu Jan 03, 2019 3:39 pm
Can you manufacture a board which will plug directly into the A3000 motherboard ROM sockets but then has the A5000 ROM 'spacing' on top?
:D
Probably! I’m actually planning on the opposite though: a board that plugs into the A5000 sockets and has the A3000 spacing on top — I don’t need to worry about board height in the A5000, so having a flash board on top of an adapter board should work fine :)

If enough (5+) A5000 owners show up wanting boards for their machines, I might do a design that’ll fit an A5000 without an adapter, but the priority after the A3000 version is one for two ROM machines like the A30x0, A4000, and Risc PC, so it won’t be for a bit.

Current project status: MCU running well and talking to the CPLD. Working on getting some signs of life out of the flash chips!
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Re: A3000 in-system programmable ROM -- any interest?

Post by Joka80 » Thu Jan 03, 2019 4:34 pm

That’s great. I would need one making as I have an 8Mb memory upgrade that was originally designed for the A5000 to fit into my A3000. Whatever the cost is I will pay it.

The A3000 motherboard could handle 4Mb max. The upgrade memory board had 4Mb which is soldered to the ROM board carrier. The factory MEMC1A was removed and a socket put in it’s place. The ROM carrier board was then connected to a twin MEMC1A board via ribbon cable which handled the 8Mb (4Mb per MEMC1A).

That’s why I need a carrier board making by your expert hands! I don’t think any electronic components as such would be needed for making an ‘adapter board’?
2F86D429-1D38-4907-8E58-921112165C77.jpeg
Board A
2F86D429-1D38-4907-8E58-921112165C77.jpeg (46.65 KiB) Viewed 1312 times
4149D9D8-8519-4979-A3FD-3EA985CB9E06.jpeg
Board B

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Thu Jan 03, 2019 4:59 pm

Joka80 wrote:
Thu Jan 03, 2019 4:34 pm
That’s why I need a carrier board making by your expert hands! I don’t think any electronic components as such would be needed for making an ‘adapter board’?
Aha, I see now :) I have one of those twin memc boards, but without the memc chips. Have been pondering making some sort of memory expansion for the A3000, but already have too many projects on the go; will be very interested to see if the twin memc setup works on your A3000 though!

If I get around to making an A5000 to A3000 adapter for my flash board, I’ll see about doing the version you need at the same time. It won’t be for a little while though. Unless anyone else on here is interested in taking this on? It’ll be a fairly simple board, although making it fit under the A3000 keyboard will require some thought.
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Re: A3000 in-system programmable ROM -- any interest?

Post by Joka80 » Thu Jan 03, 2019 6:36 pm

:D

Thanks Myelin. I am indeed interested or whoever is interested in doing it. Look forward to hearing from you.

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Sat Jan 05, 2019 7:08 am

Status update: I successfully programmed the whole 16MB of flash today... all the images from the 3QD “classic ROMs” package, plus the A3000 test ROMs.

Tomorrow I’ll try soldering on some header pins and seeing if it runs in my A3000!

Next step: figuring out how to handle switching OS. For now it’ll be something you’ll have to do over USB, but I’ve brought out some GPIO pins to a header, so if anyone has suggestions about switches etc, do post here. I imagine the Gotek users will be the experts here :)

I also bought myself a Risc PC from CJE so I can work out an adapter board or separate version of this that’ll work on the RPC and other two ROM machines. Fingers crossed!
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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Sun Jan 06, 2019 8:38 pm

IanS wrote:
Sun Nov 18, 2018 12:10 pm
Tricky to do, you waste a lot of PCB space with holes you aren't using, and with spacing as it is, different rows of pins occupy the same space.
On a 0.1" grid, the pins from one chip occupy the same space as another row of pins from another rom.
e.g.
Coloured blocks are rom chips, "X" denotes a row of pins, the "?" shows where there is a clash.
arc_roms.png
I just had a go at this, and realized that I can't stack chips on top of each other, so you actually end up withs something like this:
Screenshot 2019-01-06 11.48.40.png
Also it looks like ROM1-4 are in the opposite order on the A5000 (ROM4 on the left and ROM1 on the right, c.f. ROM1 on the left on the A3000), although it's easy enough to deal with this in software -- just program the flash in big-endian order.

I have a choice here where to put the overhang -- either over the 5th column ROM to the left, or over the serial number to the right. If there's enough room to the right, that seems like the obvious choice as it doesn't block out the 5th column ROM socket (and I think it'll work out well for Joka80 too as it'll have the A5000 board overhanging above the roms rather than over their jumpers). Ian, can you confirm if this will fit in your A5000?
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Re: A3000 in-system programmable ROM -- any interest?

Post by Joka80 » Sun Jan 06, 2019 9:20 pm

:D :D

Perfect! Looks good.

So, if you flipped the board, provided you had header pins or ROM legs where the holes would be, it would plug into the ROM sockets on the motherboard of the A3000 but on top would have the A5000 ROM socket spacing. Is this correct?

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Mon Jan 07, 2019 12:51 am

Status report: It works!

I've successfully booted the A1 diagnostic test roms (although they don't seem to respond to keypresses), Arthur 0.3 (which worked once I removed my cmorley 4MB RAM card), RISC OS 2.01, and RISC OS 3.11 on my A3000!

Arthur 1.2 wouldn't start -- anyone got any tips for getting that going on an A3000? I tried removing my IDE card, just in case ZIDEFS wasn't compatible with Arthur, but that didn't bring it to life.

RISC OS 3.11 also showed a red frame after running the POST, although this might be a bad PCF8583 or because I'm running without a battery attached.

It seems to run all right; I could run Elite off my IanS IDE mini podule, and everything else seems sane.

SYS "OS_UpdateMEMC", 64, 64 seems to work just fine under RISC OS 3.11. (Hooray for flash with 15ns page access time!)

My dual-power system (diodes feeding a regulator from both the USB 5V rail and the ROM 5V pin) seems to be working well too; I can reprogram the flash with the machine on or off, and even switching the machine off while programming the flash didn't seem to bother it. I'm not running with the actual A3000 power supply though, so I'd like someone with a working one to test this.

(to do) I haven't tried wiring up A21 yet and seeing how that works. sirbod, do you have a 4MB image I could try programming in there to test this out, or some other trick? I guess I could just *SAVE the 4MB ROM area and see what I get.

(to do) I haven't tried out any of the tools on Linux or Windows; I have both kinds of machines here though so will test those in due course.

(to do) I haven't implemented any switching to use the full memory on board; it only maps in the first 4MB right now. If the microcontroller boots fast enough, I could have that stash the current memory location in its flash, and tell the CPLD to use it when it boots.
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Re: A3000 in-system programmable ROM -- any interest?

Post by steve3000 » Mon Jan 07, 2019 1:31 am

WOW! Well done! =D>

Really great to see how you have developed this. How does the ROM switching work (or is this work in progress?).

For Arthur, I found 0.3 to be the most challenging to get working, because as you've noticed, it doesn't support >1mb. For Arthur 1.2, as I recall, this worked in my A310 with no modification, so I would expect it to do so for the A3000, providing no podules present... although possibility you may need to reset CMOS RAM?

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Re: A3000 in-system programmable ROM -- any interest?

Post by Joka80 » Mon Jan 07, 2019 1:41 am

Well done myelin! =D>

That’s great news and a massive leap forward! :D

Look forward to more updates!

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Mon Jan 07, 2019 12:54 pm

steve3000 wrote:
Mon Jan 07, 2019 1:31 am
WOW! Well done! =D>

Really great to see how you have developed this. How does the ROM switching work (or is this work in progress?).
Thank you!

Right now the process to switch OS is:

- turn off A3000
- run Python script on my Mac to upload the new OS image (takes about 30 seconds for 2MB)
- turn on A3000

However the CPLD has logic for switching on the fly; it has a “bank” variable which drives the top few bits on the flash chips’ address bus. (Top two in 4MB mode, top three in 2MB mode). I can write to this variable from the micro controller on board, so it’ll be possible to switch OS by sending a command over USB to start with. Once I’ve verified that that works (and it’ll only work if the microcontroller starts up quickly enough to tell the CPLD which bank to use before the A3000 starts accessing the ROM) I’ll start a thread asking people about favorite switches and so on, so I can add a rotary switch option or some kind of DIY thing for those who want really quick OS switching.

Another option would be to see if I can allow the host machine to switch banks, so it can access the whole 16MB (maybe with a fixed 1-2MB and a paging area above that). I don’t think the fast serial port option I was talking about will work, but paging might.
steve3000 wrote:
Mon Jan 07, 2019 1:31 am
For Arthur, I found 0.3 to be the most challenging to get working, because as you've noticed, it doesn't support >1mb. For Arthur 1.2, as I recall, this worked in my A310 with no modification, so I would expect it to do so for the A3000, providing no podules present... although possibility you may need to reset CMOS RAM?
Hmm...I tried booting up while holding Delete, although maybe it’s a different key on Arthur?
Last edited by myelin on Mon Jan 07, 2019 12:55 pm, edited 1 time in total.
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Re: A3000 in-system programmable ROM -- any interest?

Post by IanS » Mon Jan 07, 2019 1:00 pm

myelin wrote:
Mon Jan 07, 2019 12:54 pm
Hmm...I tried booting up while holding Delete, although maybe it’s a different key on Arthur?
viewtopic.php?f=16&t=12252&p=156200&hilit=rom#p156245
My Arc doesn't currently have any batteries, so I was holding delete to do a CMOS reset. Don't do that, Arthur doesn't boot. Hold R, or nothing.

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Re: A3000 in-system programmable ROM -- any interest?

Post by JonC » Mon Jan 07, 2019 1:03 pm

myelin wrote: Another option would be to see if I can allow the host machine to switch banks, so it can access the whole 16MB (maybe with a fixed 1-2MB and a paging area above that). I don’t think the fast serial port option I was talking about will work, but paging might.
If you've got 16Mb to play with, that presumable means you can have multiple OS's ready to go.
So why not implement multiboot at system start?
i.e. if more than one version of the OS is detected, present them as a couple of icons on power up. :D
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Image

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Mon Jan 07, 2019 1:11 pm

JonC wrote:
Mon Jan 07, 2019 1:03 pm
If you've got 16Mb to play with, that presumable means you can have multiple OS's ready to go.
So why not implement multiboot at system start?
i.e. if more than one version of the OS is detected, present them as a couple of icons on power up. :D
Also an excellent option!

If I can get paging working (which should be possible) this should be feasible. The system can start up in “boot mode” where it writes a bootloader into RAM, asks the user which image to use, selects it, and restarts.

I’ll have to lean on the community for help writing it; anyone interested in helping write a bootloader?
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Re: A3000 in-system programmable ROM -- any interest?

Post by cmorley » Mon Jan 07, 2019 1:42 pm

Some Kickstart switchers on the Amiga simply hook reset (and row/col from keyboard matrix) then press key & reset to switch OS. Or count multiple resets in within 1s say and change OS. Needs a reset signal flylead but is simple to use/comprehend.
Last edited by cmorley on Mon Jan 07, 2019 1:42 pm, edited 1 time in total.

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Mon Jan 07, 2019 7:24 pm

cmorley wrote:
Mon Jan 07, 2019 1:42 pm
Some Kickstart switchers on the Amiga simply hook reset (and row/col from keyboard matrix) then press key & reset to switch OS. Or count multiple resets in within 1s say and change OS. Needs a reset signal flylead but is simple to use/comprehend.
The board does have a pin for a reset flylead... I’ll give this a try also!
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Re: A3000 in-system programmable ROM -- any interest?

Post by steve3000 » Mon Jan 07, 2019 8:03 pm

myelin wrote:
Mon Jan 07, 2019 12:54 pm
Another option would be to see if I can allow the host machine to switch banks, so it can access the whole 16MB (maybe with a fixed 1-2MB and a paging area above that).
I like the sound of this, especially if you could do a keyboard scan at startup and respond to say f1, f2, f3, f4 pressed, by selecting the appropriate OS, or if no key pressed, boot to previously selected OS...? ('f' keys since the number keys are already used for monitortype selection...)

It would just require you to Initialise the IOC and then perform a handshake with the keyboard, then performing a keyboard scan is quite easy. I've written a low-level keyboard handler quite recently for RasterMan - happy to share the code.

One thing also to consider is when the OS is changed to fill the CMOS RAM with suitable defaults. Would it be possible to backup the current CMOS RAM state when switching ROMs?
myelin wrote:
Mon Jan 07, 2019 12:54 pm
Hmm...I tried booting up while holding Delete, although maybe it’s a different key on Arthur?
...did Arthur 1.2 work with switch-on+'R'?
Last edited by steve3000 on Mon Jan 07, 2019 8:03 pm, edited 1 time in total.

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Re: A3000 in-system programmable ROM -- any interest?

Post by myelin » Mon Jan 07, 2019 8:29 pm

steve3000 wrote:
Mon Jan 07, 2019 8:03 pm
It would just require you to Initialise the IOC and then perform a handshake with the keyboard, then performing a keyboard scan is quite easy. I've written a low-level keyboard handler quite recently for RasterMan - happy to share the code.
That would be amazing... could you send me a pull request on GitHub with whatever stuff you're happy to share? I've made a placeholder folder for you to put stuff into: https://github.com/google/myelin-acorn- ... bootloader
steve3000 wrote:
Mon Jan 07, 2019 8:03 pm
One thing also to consider is when the OS is changed to fill the CMOS RAM with suitable defaults. Would it be possible to backup the current CMOS RAM state when switching ROMs?
I *think* this should be possible, as long as I can establish a communications channel between the Archimedes machine and the microcontroller on my board. It'll end up being part of the bootloader -- when it selects a different OS, it'll dump the CMOS first and then rewrite it with whatever should be in there.
steve3000 wrote:
Mon Jan 07, 2019 8:03 pm
myelin wrote:
Mon Jan 07, 2019 12:54 pm
Hmm...I tried booting up while holding Delete, although maybe it’s a different key on Arthur?
...did Arthur 1.2 work with switch-on+'R'?
I just tried, but no luck -- no graphics output at all.
SW/EE from New Zealand, now in Mountain View, CA, making BBC/Electron hardware projects for fun.
Most interesting: Arcflash, FX2+PiTubeDirect Tube/Cartridge adapter, USB cart interface.

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IanS
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Re: A3000 in-system programmable ROM -- any interest?

Post by IanS » Mon Jan 07, 2019 8:55 pm

myelin wrote:
Mon Jan 07, 2019 8:29 pm
I just tried, but no luck -- no graphics output at all.
Where did you get the Arthur 1.20 roms? Are they exactly 512K in size? The first set I found didn't work. Try the ones from 4corn - http://www.4corn.co.uk/archimedes.php

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