Very nice to see new circuit boards! I hope they meet your expectations.myelin wrote:I've been looking forward to these PCBs showing up
I haven't had any luck getting my Elk to work with its Plus 1 attached, and haven't had any luck finding another affordable one on eBay, so I went ahead and designed this thing. It's basically just the cartridge circuitry of the Plus 1, except with a third cartridge socket, and a CPLD instead of the discrete logic.
I'm not particularly proud of the wiring; despite spending ages trying to get all the signals cleanly out of the expansion connector and to the cartridge slots, what I ended up with was kinda messy and loopy, but with any luck it'll work.
Also pictured: a couple more variants on my 32kB flash cart.
This might help to answer that.roland wrote:Why are your boards copyright by Google Inc?
ExactlyThomasHarte wrote:This might help to answer that.roland wrote:Why are your boards copyright by Google Inc?
Pretty much every employment contract in California gives the employer rights to anything you do on company time, using company equipment, or (and this is the kicker) relating to the company's business... and Google has business in just about every conceivable field. If you want to do a personal project while employed at Google, there's a process to get the company to formally disclaim any interest in the project, but if you're releasing it as open source anyway, it's easier to just release it as an unofficial Google project, which means that browsing Stardot at work, soldering up boards using the EE lab at the office, etc, are all fine. I'd rather be able to use my company laptop and occasionally spend company time on this than have my own name on the copyright.Don't believe anything they say: Google are looking to corner the Electron peripherals market!ThomasHarte wrote:This might help to answer that.roland wrote:Why are your boards copyright by Google Inc?
Resistance is futile!paulb wrote:Don't believe anything they say: Google are looking to corner the Electron peripherals market!
Did you click on the link I posted above? That is what the thread covered but dont think it moved much. Would be good if Myelin picked up the mantle.algenon_iii wrote:Nice idea, considerably more compact than a Plus 1 as well.
As an aside, has anyone ever considered an Electron Plus+? Basically a single expansion that gives all of the BBC B ports (and ROM sockets) in one handy unit that plugs into the back of the electron (perhaps retrofitted into a Plus 1 case).
That's pretty much it. The overall plan here is just to make interesting things for the Electron, with a preference toward making stuff that (a) nobody else is working on already and (b) I can actually test. So things like Tube and 1MHz Bus interfaces are off the table for now because (a) Dave Hitchins already has that taken care of with the New AP5 and (b) I don't have any Tube/1MHz hardware here so I'll have no way to know if I've gotten it rightElminster wrote:It must be the drugs but looks like you glued your Electron to the ceiling!
So is the issue that you current Plus 1 is busted so you have decided to reengineer the cartridge bit?
Edit: Have you thought about taking on this project? Sounds like you are half way there already and in your interest as you have no plus 1
Think there are several more kicking about and many discussion in the pub/inn/tavern over the years. Just need to some one to build it. And I think you probably now the closest as most people have added to or moded exiting plus1. You have built a semi replacement. I'll give you a few weeks to knock up the everything design, I'll expect my prototype bored in a few months ?Looks like we've actually got two "New Plus 1" threads btw: Plus 1, TNG and Redesign Electron Plus1.
Looks like this is the NZ version with the photo upside down!myelin wrote:
I'm also working on getting my Elk PiTubeDirect cartridge working. It seems promising (all the debug code is working properly, and I can read out the Tube startup banner from BASIC), but the OS isn't talking to the Tube yet, because I don't have the Tube Host code installed anywhere.
minus_one and elk_pi_tube_direct.jpeg
I think this is the best strategy, too. It would be nice to have some enhancements to the cartridge connections, though, adding the missing address pins, for instance. Maybe there would need to be a separate connector for these extra pins to prevent compatibility issues. You wouldn't want to mess around with different connector widths, certainly.myelin wrote:The problem with making one big project that does absolutely everything is that you need to redo the whole thing after realizing you missed that one critical feature. I think I'd rather make a "Minus Six" with just six cartridge slots and nothing else, and do the rest as cartridges.
Ahh... this is such a can of worms! Whenever I start thinking about this, I usually end up concluding that the current cartridge spec, annoying as it can be, is good enough -- it's standard, supported by a ton of hardware, gives access to &FCxx and &FDxx, and gives each cartridge two sideways bank IDs that are guaranteed to not conflict with anything.paulb wrote:I think this is the best strategy, too. It would be nice to have some enhancements to the cartridge connections, though, adding the missing address pins, for instance. Maybe there would need to be a separate connector for these extra pins to prevent compatibility issues. You wouldn't want to mess around with different connector widths, certainly.
I have looked at the thread now, but hadn't when I first wrote my message.Elminster wrote:Did you click on the link I posted above? That is what the thread covered but dont think it moved much. Would be good if Myelin picked up the mantle.algenon_iii wrote:Nice idea, considerably more compact than a Plus 1 as well.
As an aside, has anyone ever considered an Electron Plus+? Basically a single expansion that gives all of the BBC B ports (and ROM sockets) in one handy unit that plugs into the back of the electron (perhaps retrofitted into a Plus 1 case).
I think the Jafa Mode 7 Adapter intercepts (but does not override) address accesses in the complete memory space in order to know what the ULA is transferring to the screen. Certainly, it appears to track what is being written to the ULA registers. Without knowing the upper address bits, cartridges cannot know what is really going on in general on the address bus.myelin wrote:Having access to the rest of the address pins would let you do clever things like bus monitors, but unless you want to disconnect the ULA (and lose the keyboard, cassette port, RGB output, etc) or desolder the OS ROM, you won't be able to respond to any memory accesses outside the cartridge space anyway, which makes that less appealing. I have a PCB here that will let me hook an FPGA up to the expansion port and mess around with that sort of stuff, but despite all my brainstorming, I haven't come up with anything else that would really take advantage of the extra pins...
I wonder if we could make an expansion that keeps NMI low all the time to disable the ULA, for a fast MODE 2 etc.
Ooh, I didn't think of that. With the CPLD I could make nOE, nOE2, nINF*, MADET, and maybe some other Elk/Master signals software selectable, which would allow for this sort of thing.1024MAK wrote:At least one pin, maybe two on the cartridge slot are not used by 99% of cards. There may be one or two other pins where the signal is hardly used by cards.
Indeedfordp wrote:I would add two things to this project to make it MUCH better.
1) SD Card Slot to use David Bank's Printer Port MMFS.
2) A built in Flash Chip that emulates at least one cartridge (May as well be able to emulate 3 cartridges in one chip) to allow MMFS with just this board.
It would be pretty feasible to add four banks of sideways RAM and four banks of flash, which would result in a memory layout kind of like on the Master.Sort of! I should warn you that the Minus One isn't exactly an "end user" product like the Plus One; it's a lot cheaper and lets you have three cartridges rather than two, but:DBCohen wrote:I had a Plus 3 back then, but I know that is sold long ago. Seems a Plus One should be the way to go to allow some Roms or disk access via the slots, but eBay has none and the pricing on their seems to have gone stupid! I have seen the GoSDC thing, but that seems a tad pricey for a single function board. Cartridge slots would allow me to do a lot more.
Is there somewhere I can buy these Minus One boards (made up, that is; I can't solder for toffee)?
There have been various case fabrication projects for cartridges on here, but nothing for Electron expansions yet. If you're in the USA, I can solder one for you, and if you're in the UK I believe there's a couple of people on here that have offered to help solder. The components on the board cost around US$15-16.
