Redesign Electron Plus1

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roland
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Redesign Electron Plus1

Post by roland » Sun May 01, 2016 9:54 am

Duikkies thread about the USB CH375B and the Electron ( viewtopic.php?f=3&t=11024 ) made me start fantasising about a new design for the Plus1. Of course, we can simple design a pcb that fits into a slot of the Plus1 and provide the necessary connectors.

But if we design a complete new Plus1 with a cpld for decoding and SWR bank switching I think there is plenty of room on the board to add a 6522 VIA and the connector for the CH375B board. There is also room for SW-RAM (e.g. a 128KB chip) and the Plus1 ROM and DFS for the CH375B (in one EEPROM).

When this board has so much room for additional SWRoms, it won't hurt to sacrifice one cartridge slot and we can create a new one with one or two connectors for the Tube and a BBC compatible user port. Maybe we can also work out a 1 MHz bus connector as well. This will certainly fit if the dust cover around the cartridge slots is removed.
Acorn_Plus1D.jpg
Picture copied from Chris's Acorns
The most important chips on the board will be:
  • EEPROM for Plus1 ROM and DFS
  • 128KB RAM for SW-Ram (non-battery backup but with write protection
  • ADC0844 (still available on Ebay and Farnell)
  • 74LS273 for printer port
  • 6522 for user port
  • CPLD for decoding logic, maybe with a 74LS30 to save a couple of input lines.

If you have a Plus1 then you can simply exchange the boards without destroying the housing. If you don't have a Plus1, you'll have one without housing.

Any thoughts about this project?
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sydney
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Re: Redesign Electron Plus1

Post by sydney » Sun May 01, 2016 10:46 am

I've thought about something similar for years. I'd probably lose the printer port and analogue port in favour of a user port, tube and 1mhz bus. Might put retrohard are out of business though!

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Re: Redesign Electron Plus1

Post by duikkie » Sun May 01, 2016 11:52 am

you may leave the plus1 alone and make a in between plus 0 like the plus3

plus 0 with connector to the electron and at the order side a connector for the plus1.

i think the elektron is growing :)

elektron + plus3 +plus0+plus1 :)

what is the story for plus2 ??? never seen a plus 2 ??

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Re: Redesign Electron Plus1

Post by dixiestoat » Sun May 01, 2016 12:25 pm

What a super idea...an all singing all dancing Plus 1.. :D
If in doubt, CTRL-BREAK thou should clout..

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Re: Redesign Electron Plus1

Post by JonC » Sun May 01, 2016 12:31 pm

Would it be AP6 compatible? :mrgreen:
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Re: Redesign Electron Plus1

Post by CMcDougall » Sun May 01, 2016 1:19 pm

would be good Roland, and as Simon said, what is a printer :? :lol:
duikkie wrote:what is the story for plus2 ??? never seen a plus 2 ??
you have now :shock:
none made by Acorn, but Slogger made the Plus2, but they don't have housing.
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Re: Redesign Electron Plus1

Post by paulb » Sun May 01, 2016 1:22 pm

roland wrote:Duikkies thread about the USB CH375B and the Electron ( viewtopic.php?f=3&t=11024 ) made me start fantasising about a new design for the Plus1. Of course, we can simple design a pcb that fits into a slot of the Plus1 and provide the necessary connectors.

But if we design a complete new Plus1 with a cpld for decoding and SWR bank switching I think there is plenty of room on the board to add a 6522 VIA and the connector for the CH375B board. There is also room for SW-RAM (e.g. a 128KB chip) and the Plus1 ROM and DFS for the CH375B (in one EEPROM).

When this board has so much room for additional SWRoms, it won't hurt to sacrifice one cartridge slot and we can create a new one with one or two connectors for the Tube and a BBC compatible user port. Maybe we can also work out a 1 MHz bus connector as well. This will certainly fit if the dust cover around the cartridge slots is removed.
It starts to sound like another Plus unit altogether. I wouldn't want to sacrifice cartridge slots - I've said before that Acorn should have put a slot in the Electron itself - but I might imagine making them bigger for more spacious cartridges. If you take one away, you then start to impact use of peripherals such as disk interfaces. Although you might still be able to use, say, a ROM with a disk system, there's a degree of convenience lost even if that handles a particular person's use-case.

It does look like more could have been put in the original Plus 1, if physical space is the only concern, and I guess that Acorn missed a trick by not putting sockets on the board intended for certain expansions, just as they did for the Archimedes where you had a serial port but it didn't work unless you got the upgrade (if I recall correctly) and like the Econet hardware on most of their machines. Of course, it was penny-pinching when they did it on the Archimedes. :evil:

That said, the aim with the Plus 1 and the Electron in general was that you wouldn't open up the cases to add stuff, which is how they ended up with cartridge ports. Perhaps mini-cartridges might have been an interesting option, just like there was a mini-podule thing for the Archimedes (which maybe Dave H had a hand in).
roland wrote:The most important chips on the board will be:
  • EEPROM for Plus1 ROM and DFS
  • 128KB RAM for SW-Ram (non-battery backup but with write protection
  • ADC0844 (still available on Ebay and Farnell)
  • 74LS273 for printer port
  • 6522 for user port
  • CPLD for decoding logic, maybe with a 74LS30 to save a couple of input lines.

If you have a Plus1 then you can simply exchange the boards without destroying the housing. If you don't have a Plus1, you'll have one without housing.

Any thoughts about this project?
It sounds like a nice project. I did have vague plans about re-making the case, but I didn't get into doing so. In fact, I was more interested in doing various cartridge interfacing things instead.

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Re: Redesign Electron Plus1

Post by JonC » Sun May 01, 2016 1:51 pm

It would make sense to put commonly used ports on the Plus1 if you were going to redesign it.
User Port, Tube, 1 Mhz Bus, USB, Econet etc, and then the cartridge slots become what they were before; a place to add new peripherals. :D

Of course getting people to agree to what are 'commonly used ports' could be open to 'discussion' :lol: :mrgreen:
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Re: Redesign Electron Plus1

Post by daveejhitchins » Sun May 01, 2016 1:58 pm

I think the case should stay e.g. don't make a board that doesn't fit into the existing case. Is there enough room, around the edges, for all the connectors that people want . . . Probably(?). So keep the existing printer and analogue ports and just add the rest (they don't have to be poking out of the back edge! It's got sides too :D ). And, keep the two cartridge slots. Any components that need to be in the area of the cartridge tray can be underneath the board, so keep the tray too. IMO it's got to look smart, which the current box does.

Use one large PLD or FPGA which ever is the lower cost . . . I know a UK source for some Xilinx XC9536 (may not be big enough though?). This along side the ULA Dave's (hoglet) doing would make it a pretty awesome machine.

May have to look at the power supply . . . With everything connected I thing the current one may struggle! However, there are plenty of good parts, out there, that will do the job admirably.

This would be a big project . . . I think people may need to order up-front. Just purchasing the parts will be costly, let alone organising, kitting, building (for those that can't), shipping and troubleshooting. There was mention of me not charging enough for building the AP6 . . . That, actually, was the easy part! Kitting takes longer :lol:

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For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Redesign Electron Plus1

Post by paulb » Sun May 01, 2016 2:54 pm

daveejhitchins wrote:Use one large PLD or FPGA which ever is the lower cost . . . I know a UK source for some Xilinx XC9536 (may not be big enough though?). This along side the ULA Dave's (hoglet) doing would make it a pretty awesome machine.
At some point, if I ever get round to doing so, I'll take a closer look at the Lattice iCE40 stuff given that there's a fully open toolchain for it, thanks to IceStorm and Yosys.

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Re: Redesign Electron Plus1

Post by dixiestoat » Sun May 01, 2016 4:45 pm

All those lovely ports...Mmmm... [-o< [-o<
Us Bears of little Brain love the ease of plugging stuff in... :D :D
If in doubt, CTRL-BREAK thou should clout..

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Re: Redesign Electron Plus1

Post by daveejhitchins » Sun May 01, 2016 5:08 pm

OK, I've been dreaming thinking about this project. We've the AP5 content (Tube, IMHz bus, User Port [with an extra socket for the second port on the 6522]), a socket for MartinB's serial port, a socket for MartinB's I2C, ECONET, AQR (support is there already, for RAM disc, in ACP's ADFS), Contents of AP6 . . . . Anything I've missed?

Dave H :D
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Products: ARA II, ARA III, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Redesign Electron Plus1

Post by JonC » Sun May 01, 2016 5:11 pm

Just had a thought: You could make the tube interface internal so you can plug Jason's co-pro into it internally. :idea:

Also why not take the approach of the slogger rombox plus and mount 4 rom sockets on top of the empty space next to the cartridges? :idea:

\:D/
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Re: Redesign Electron Plus1

Post by dixiestoat » Sun May 01, 2016 5:48 pm

All these ports..be just like a Model B..

Now can somebody spray the keyboard black..paint the top row red... :D :D
And somebody's gonna Photoshop that now aren't they..... :D :D :D

Joking aside...this is exciting... =D> =D>
If in doubt, CTRL-BREAK thou should clout..

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roland
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Re: Redesign Electron Plus1

Post by roland » Sun May 01, 2016 7:11 pm

Thanks for your thoughts and ideas. I had a look at the AP6 board and I just want to avoid to have six sockets for roms. There must be 1 socket for ROM which will contain both the Plus1 stuff and a patched DFS to use the CH375b. And there will be a large ram chip, for example an 128KB which can contain eight banks of 16K for sideway roms. The CPLD logic will take care for selecting the right bank of this RAM. That's the only way to save space for all the other goodies.

I was thinking about removing the trays to avoid cutting the Plus1 case. The connectors can be placed next to the current slots. Placing the co-pro board inside the Plus1 makes it easier to place all the new connectors next to the cartridge slots, but makes it harder to swap the board between the Elk and another computer (or should I just buy another co-pro board to solve that issue :) )

Although I don't use the printer and analogue port of the Plus1 IMHO they have to stay for people who do use them.

And let us focus on the people who really "need" this expansion. If you have a disk drive or Elk MMC, do you really need the USB storage? If you need the other ports, there is the AP5. My idea is to build an extension to the Electron with storage, some SWR, and a bit more of I/O like a user port and 1 MHz bus.

On the soft side ... I really don't have any idea how the USB storage will ever be reachable from the co-pro. Does it also use disk images? Is software available for that? I still have many things to investigate and I'm not that familiar with the Electron. I'm more into the Atom as you probably know. But I like challenges :)
256K + 6502 Inside
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Re: Redesign Electron Plus1

Post by paulb » Sun May 01, 2016 8:52 pm

An interesting thing I just found in Electron User on the topic of unrealised expansions: see "Piggyback interface for the Electron" from Electron User volume 1 number 5 February 1984 page 8.

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Re: Redesign Electron Plus1

Post by ThomasHarte » Mon May 02, 2016 12:34 am

A feature that I think would be nice: a register that one can write to in order to raise or lower the NMI line. Its purpose would be that if, like many games, I decide only to use a small portion of the display, I can programmatically assert NMI in the interim such as to get 1Mhz RAM access for the blanked period even if I'm in one of the 80-column modes.

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Re: Redesign Electron Plus1

Post by sydney » Mon May 02, 2016 6:29 am

paulb wrote:An interesting thing I just found in Electron User on the topic of unrealised expansions: see "Piggyback interface for the Electron" from Electron User volume 1 number 5 February 1984 page 8.
I think you linked to the wrong issue, here is the right one:

electron user

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Re: Redesign Electron Plus1

Post by paulb » Mon May 02, 2016 8:33 am

sydney wrote:
paulb wrote:An interesting thing I just found in Electron User on the topic of unrealised expansions: see "Piggyback interface for the Electron" from Electron User volume 1 number 5 February 1984 page 8.
I think you linked to the wrong issue, here is the right one:

electron user
Yes, clipboard issue! :oops:

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Re: Redesign Electron Plus1

Post by Elminster » Sun May 07, 2017 8:37 pm

With the new AP5 just around the corner, hopefully, I guess this will be the next project [-o<

I agree with most.

Keep everything plus 1 has, add all the features of new AP5 & 6.

Extra bits I would like on top of plus 1,5&6 :
- As well as external tube port, an internal one that will take a raspberry pi zero (like spectrum next)
- econet, but like master version easy to convert to Ethernet
- teletext chip to allow hardware mode 7, I.e. Roll in the Jaffa hardware mode 7

Food for Roland/Dave's thoughts

Edit: if I understood how RobC's bbc video system upgrade worked I would add that, but assume that would need to go in electron if it was modded for electron.

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Re: Redesign Electron Plus1

Post by awilliams » Sun May 28, 2017 1:23 pm

> - econet, but like master version easy to convert to Ethernet

I am pretty sure you can't do Econet on an Electron because of inadequate FIQ latency in hires screen modes.

There were a pile of these
http://www.beebmaster.co.uk/Econet/ElkNet.html
about when I worked at Barson Computers, I didn't ever try one as I was told they didn't work. I suspect that the timing issue might have been overlooked by the guys who designed it. They had both gone by the the time I started so I never investigated it further. I have an unpopulated board for it though.

So if you want to try econet on an Electron you may need a fpga implementation of the 68B54 with a much longer fifo than normal and you may get it to work.

I stand to be corrected on any of the above its been a long time....

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Re: Redesign Electron Plus1

Post by danielj » Sun May 28, 2017 1:32 pm

It has been done, it does require-slow-o-net speeds though IIRC:

viewtopic.php?t=7769

d.

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