Myelin's USB Electron Cartridge Interface

[myelin]

PROJECT STATUS: built and tested, and it works fine! I don't have any built up ones for sale, but will post you a circuit board for free if you can acquire the components and solder it yourself. (Updated May 22, 2019 -- I have three boards available.)

PCBs arrived in the mail today, and I just soldered up the first board!

CPLD + AVR + cartridge socket, so I can talk to Electron cartridges from my Mac.

PCB and untested VHDL: https://github.com/google/myelin-acorn- ... programmer

[myelin]

Success! Just got it to read out a Countdown to Doom cartridge

[davidb]

Well done! This looks like it could be very useful for programming EEPROM/Flash cartridges - would it work for that purpose?

[myelin]

Well done! This looks like it could be very useful for programming EEPROM/Flash cartridges - would it work for that purpose

Yep! That's the next thing I'm going to work on; right now it reads just fine but I haven't implemented writes (RnW is always high right now) or access to &FCxx/&FDxx. I made this mostly for debugging, but also so I can program flash cartridges outside the Electron. I haven't been able to find a way to tell the Electron to ignore cartridges on boot, which means that a cartridge containing code that causes a crash on startup is effectively bricked unless you have an external programmer like this.

I've just soldered up the one board, but I have a stack of 9 more PCBs if anyone is interested in one, and I'm happy to part with a few of them at cost for folks I know will make good use of them There's about US$11 of parts on there, and it looks like shipping to the UK would be about US$14, so we're talking about US$25 or £20 (although I could possibly ship a few to one person and have them distribute them).

[sirmorris]

nice board!

[1024MAK]

nice board!

Yep . An interesting idea

Mark

[1024MAK]

I haven't been able to find a way to tell the Electron to ignore cartridges on boot, which means that a cartridge containing code that causes a crash on startup is effectively bricked unless you have an external programmer like this.

The normal way of doing this in hardware, is to have a two pin header / link / jumper shunt in series with the EEPROM or EPROM /CS (/CE) control line pin, with a 10k pull up resistor on the EEPROM or EPROM side. A production PCB can have the two link pads joined via a thin track. While on a development PCB, you cut the track, then either use a jumper shunt, or wire the pin header to a SPST switch

I've just soldered up the one board, but I have a stack of 9 more PCBs if anyone is interested in one, and I'm happy to part with a few of them at cost for folks I know will make good use of them There's about US$11 of parts on there, and it looks like shipping to the UK would be about US$14, so we're talking about US$25 or £20 (although I could possibly ship a few to one person and have them distribute them).

I'm interested

Whereabouts in the world are you? As you are using US$, are you in the USA? One consideration we folk in Europe have for items sent from outside the EU, is import tax. For the UK, anything costing £15 of more, including the cost of postage will be charged VAT plus an handling fee of £8. VAT is currently 20%.

So at the current exchange rates, anything approaching US$19 gets us near the threshold . Now, it may actually work out cheaper to take the tax hit in one go and ship everyone’s boards in a single package from you rather than sending individual packets to individuals. Hence me giving you the details.

If you can let me know the size of the PCB, I can work out the cost of postage within the UK. And if required, the cost to other EU countries.

I'm happy to forward the PCBs to other Stardot members if you would like me to.

Mark

[sirmorris]

Or just lie on the customs form. Just saying. Don't judge me.

[1024MAK]

Or just lie on the customs form.

"You might very well think that; I couldn't possibly comment..."

Mark

[sirmorris]

And so the house of (expansion) cards falls..

[myelin]

I'm interested

Whereabouts in the world are you? As you are using US$, are you in the USA? One consideration we folk in Europe have for items sent from outside the EU, is import tax. For the UK, anything costing £15 of more, including the cost of postage will be charged VAT plus an handling fee of £8. VAT is currently 20%.

So at the current exchange rates, anything approaching US$19 gets us near the threshold . Now, it may actually work out cheaper to take the tax hit in one go and ship everyone’s boards in a single package from you rather than sending individual packets to individuals. Hence me giving you the details.

If you can let me know the size of the PCB, I can work out the cost of postage within the UK. And if required, the cost to other EU countries.

I'm happy to forward the PCBs to other Stardot members if you would like me to.

I'm in San Francisco, so it sounds like the tax thing is going to be pretty unavoidable, unless someone over there wants to acquire components and do the assembly, in which case I'd be happy to post over a few PCBs. The £8 handling fee and the postage means that sending them in bulk and having you forward them out is almost certainly the best plan.

FYI I'm working on a few other things that folks may be interested in... a simple expansion ("Minus One") that gives three cartridge slots (but none of the other features of the Plus One), and also a 32k dual ported SRAM cartridge that you can read/write over USB as well as from the Electron. And some more flash cartridge designs (one that's super short, so it barely pokes out the top of the Plus One, and one that is exactly the same form factor as the PCBs in the Acornsoft cartridges). So you may or may not want to wait until I have more designs to send over as well

[daveejhitchins]

Just a thought . . .

Could we get the boards made from this end? That's if you're willing to share the board Data?

Dave H

[davidb]

See the link in the first message, Dave.

[myelin]

Yup, that's absolutely fine! Double check with me before ordering anything so I can make sure the latest gerbers etc are up on github, but this is all open source and I'd love it if you or anyone else here would like to make some

[atcurtis]

Interesting... Although I have a BBC Master.

btw, is there an Acorn fan/user group in the San Francisco bay area? I'm in the south bay area.

[daveejhitchins]

See the link in the first message, Dave.

I probably read that, but it was earlier than yesterday . . . You can't ask me to remember everything

If anyone is interested I'll be willing to host the purchase and distribution?

Dave H

[myelin]

Interesting... Although I have a BBC Master.

btw, is there an Acorn fan/user group in the San Francisco bay area? I'm in the south bay area.

Oh good, someone else in this part of the world! I grew up in New Zealand, where Acorn machines were pretty dominant for a while, and wasn't sure if anyone else in the Bay Area knew about them There's a guy here at the SF Google office who nearly worked for Tynesoft (they went out of business before his internship started). No idea if there's an official group, although I imagine if we keep mentioning SF on Stardot, more of us Bay Area folks will come out of the woodwork!

[sydney]

myelin, atcurtis - you guys have seen the google maps thread, haven't you?

http://www.stardot.org.uk/forums/viewto ... =41&t=8933

[myelin]

If anyone is interested I'll be willing to host the purchase and distribution?

Excellent I'd like to verify that I can get writes working to cartridges before recommending ordering any boards. I'll keep you posted on that -- have quite a bit on for the next couple of weeks so it may be a little while.

[atcurtis]

myelin, atcurtis - you guys have seen the google maps thread, haven't you?

http://www.stardot.org.uk/forums/viewto ... =41&t=8933

Now I have.

[atcurtis]

Interesting... Although I have a BBC Master.

btw, is there an Acorn fan/user group in the San Francisco bay area? I'm in the south bay area.

Oh good, someone else in this part of the world! I grew up in New Zealand, where Acorn machines were pretty dominant for a while, and wasn't sure if anyone else in the Bay Area knew about them There's a guy here at the SF Google office who nearly worked for Tynesoft (they went out of business before his internship started). No idea if there's an official group, although I imagine if we keep mentioning SF on Stardot, more of us Bay Area folks will come out of the woodwork!

I am British and I grew up in England. I just live/work in the SF bay area these days. I wasted a lot of time playing Elite in my youth

[myelin]

If anyone is interested I'll be willing to host the purchase and distribution?

FYI I've verified that writing to cartridges (everything that uses nOE or nINFC, at least) works over the USB interface. I could read out all 256 ROM images from my MGC (by writing 0 to &FC08 and then cycling through setting &FC00=0 to 127 and reading banks 0 and 1).

How about I post you a few PCBs and you can decide what to do with them? No cost; I don't need all of mine so you can have as many as I can convince USPS to post over without charging me a fortune

[daveejhitchins]

Yes please I'll ensure that people who will actually make good use of these will have one.

Many thanks - Dave H

If anyone would like a board, please pm me.

[myelin]

It took me four and a half months to get around to it, but I finally posted some of the boards off to Dave Totally unassembled, so there'll be a bit of pottering around to get them working, but folks in the UK might finally get to play with these in a little bit!

[daveejhitchins]

If anyone would like a board, please pm me.

^^^ Just a reminder.

Thanks Phil . . .

Dave H

[8bitkick]

Interesting... Although I have a BBC Master.

btw, is there an Acorn fan/user group in the San Francisco bay area? I'm in the south bay area.

Oh good, someone else in this part of the world! I grew up in New Zealand, where Acorn machines were pretty dominant for a while, and wasn't sure if anyone else in the Bay Area knew about them There's a guy here at the SF Google office who nearly worked for Tynesoft (they went out of business before his internship started). No idea if there's an official group, although I imagine if we keep mentioning SF on Stardot, more of us Bay Area folks will come out of the woodwork!

San Jose here! Relocated Brit. Acorn Atom, BBC, Electron and A3000 seemed to follow me here...

One idea crossed my mind - get down to Vintage Computer Festival West next year with Acorn machines and represent!

http://vcfed.org/wp/festivals/vintage-c ... ival-west/

[daveejhitchins]

One idea crossed my mind - get down to Vintage Computer Festival West next year with Acorn machines and represent!

Oh yes . . . You've just got to go when they're saying this:

Don’t forget — CHM is the world’s best computer museum . . .

and check-out if they have the full Acorn kit!

If you need anything (?) I'm sure we should be able to assist, somehow!

Dave H

[8bitkick]

One idea crossed my mind - get down to Vintage Computer Festival West next year with Acorn machines and represent!

Oh yes . . . You've just got to go when they're saying this:

Don’t forget — CHM is the world’s best computer museum . . .

and check-out if they have the full Acorn kit!

If you need anything (?) I'm sure we should be able to assist, somehow!

Dave H

Thanks Dave! The CHM (where they host VCFW yearly) is excellent... I have a membership ... they do have a beeb there I've seen at least http://www.computerhistory.org/atchm/the-bbc-micro/

Along with an Apple I signed by Woz and the original Apollo Guidance Computer that is

VCFW happens yearly and enthusiasts come along to demo their working machines. Would love to join some stardot friends there and represent acorn machines

I will start a seperate thread to see if/how we can get a California ABUG going

[daveejhitchins]

I have four three of these boards available. If you'd like one, please pm me with your details (if I haven't already got them) Postage costs only, first class large letter.

One board per person, first come etc.

If you'd like me to fit the SMD parts just send them along.

Dave H

Other boards from myelin:
Flash Cartridge

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Acorn Electron PitubeDirect Interface
    I have four three two of these boards available - same rules as above.

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