Simple Electon MMC Interface

[hoglet]

Hi Guys,

A couple of days ago I received a Plus One from Dave H. Many thanks for this! After opening it up and having a good look at the schematic, I thought it might be possible to hook at 99p MMC interface directly up to the printer port.

The first issue with this is there is no +5V present, but that's easily fixed with a wire:

There are several unconnected pins on the printer port (21..26). I chose pin 26 as this is typically connects to an input on the printer. Which means if you want to occasionally connect a printer than nothing bad should happen. If I had a 100mA PPTC resettable fuse to hand then I would have probably included that as well.

The following connections were then used between the Elk and the SD Card interface:

Code: Select all

Electron      SD Card
   2 GND ===> GND   (Black)
   3 PD0 ===> MOSI  (Grey)
   5 PD1 ===> SCLK  (White)
  10 GND ===> CS    (Blue)
  19 ACK <=== MISO  (Purple)
  26 +5V ===> +5V   (Red)

The ROM cartridge contains a new build of MMFS 1.29 specially for the Elk printer port:

To support the Plus One printer port, a new device is needed in MMFS:
https://github.com/hoglet67/MMFS/blob/m ... kPlus1.asm
The only part of this that's really new is the subroutines starting with P1_ that do the bit banging of the clock and data. The rest is pretty much the same as for the user port.

And here it is working:

Speedwise, this will be a bit slower than MMFS connected to an EUP, but honestly it's not too bad at all.

If anyone wants to build one, then you need the latest release of MMFS (currently 1.30), and the build you need is in the "E" directory.
https://github.com/hoglet67/MMFS/releases

Dave

[sydney]

Fantastic work Dave
Might have to get an elk now.

[jms2]

Nice work Dave - although I don't need to do this as I already have EUP.

What does interest me is your MMB image, which contains Electron games. I was thinking of putting one together myself as I thought that nothing similar existed online. Where did you get this one from, or did you make it?

[hoglet]

What does interest me is your MMB image, which contains Electron games. I was thinking of putting one together myself as I thought that nothing similar existed online. Where did you get this one from, or did you make it?

It was created by Ray Harper:
http://www.stardot.org.uk/forums/viewto ... 62#p117962

[rharper]

Nice work Dave - although I don't need to do this as I already have EUP.

What does interest me is your MMB image, which contains Electron games. I was thinking of putting one together myself as I thought that nothing similar existed online. Where did you get this one from, or did you make it?

It's mine all mine
I forget which thread it is already in but here it is again.
Ray

[davidb]

Looks good! I searched for similar projects elsewhere and found this one (via Hackaday).

[daveejhitchins]

That's great work Dave . . .

What's needed now is some kind person to knock-up a design for a printed case so that the interface can just plug into the back of the Electron - no wires! The more options for the Electron the better

Dave H

[davidb]

Is there a way to avoid having to modify the parallel port connections?

[MartinB]

Prior to my producing EUP, I did almost exactly the same thing with the Elk Pus 1 Printer port but my implementation was for an UPURS interface (of course!) It is on the forum somewhere (with a video) but I think it's in the forum search 'black hole' so I can't find it just now . I was however talked out of the idea by the wider forum audience because Plus 1 mods were considered a no-no since they'd likely rule out too many potential users. Consequently and subsequently, EUP was born....

EDIT : Found it! (...by manual means )

viewtopic.php?f=12&t=3114&p=44957#p44957

[CMcDougall]

Nice
I can see my other 2 plus1s having a new 5v wire on them!

its about time someone done a 510 menu driven Discs from the Acorn World DVD....

[duikkie]

there is a mode6 menu like the mode7 menu for beeb.mmb , somewhere uploaded on this form

[duikkie]

with a little fix you can change the rom in the plus 1 in a bigger prom , maybe holding the rom software , then no slot needed

[myelin]

Nice job using the ACK line to get data back in! I'd written off the Plus 1's printer port for anything useful because I thought it was output-only

[1024MAK]

An output only port is sometimes useful (I use it for testing various LED displays). But yes, the single input line can be used. It is however a lot more limited compared to the 4 to 5 input bits on a full function port.

If you don't want to modify the Plus 1, you could always pick up the +5V from somewhere else. I'm mobile at the moment so can't check, but the analogue port may have a +5V line...

Mark

[davidb]

I was just wondering whether one of the other pins on the parallel port could be set high and used to power the MMC interface. I'm guessing that this wasn't an option given that the Plus 1 needed to be modified in the end.

[myelin]

I was just wondering whether one of the other pins on the parallel port could be set high and used to power the MMC interface. I'm guessing that this wasn't an option given that the Plus 1 needed to be modified in the end.

The pins are driven by a 74LS373 or 74ALS373. Looking at some datasheets, it seems that both of these can source 2.6 mA, and will produce a voltage output of 2.4-3.3V while doing so. I don't have any strong specs for SD cards, but read somewhere that they need more like 80 mA, so you're probably out of luck powering one from a logic pin.

[myelin]

If you don't want to modify the Plus 1, you could always pick up the +5V from somewhere else. I'm mobile at the moment so can't check, but the analogue port may have a +5V line...

Looks like +5V comes out on pin 1:

[hoglet]

We did consider trying to drive the SD Card off the other output pins, but there just isn't sufficient current.

Looks like +5V comes out on pin 1:

That's a good spot.

Do you have a link to the full Plus One schematic?
Edit: Found this, see below...

I've been working from Phill's re-drawn schematic:
download/file.php?id=1615
which I think incorrectly shows only -5V being available on the Analogue port.

So yes, this would be a good option for people who don't want to mod.

Dave

[DigitalDunc]

Fantastic work Dave
Might have to get an elk now.

I have a few spare Elks and if you want one FOC just let me know.

[hoglet]

Do you have a link to the full Plus One schematic?

I found a high quality copy of the original Acorn Plus One schematic here:
viewtopic.php?t=10413#p125767
Thanks to Steve Bagley for scanning this.

Dave

[paulb]

Do you have a link to the full Plus One schematic?

I found a high quality copy of the original Acorn Plus One schematic here:
viewtopic.php?t=10413#p125767
Thanks to Steve Bagley for scanning this.

Yes, that is so much clearer than the one I was using. Thanks to Steve from me, too!

[hoglet]

Hi Guys,

Here's an updated version of MMFS that fixes a bug in SAVE with the Electron Plus One:
https://github.com/hoglet67/MMFS/releases

From now on I'm going to be using github as a repository for MMFS releases, rather than attaching them to forum threads.

Dave

[CMcDougall]

^ not noticed that bug yet, as was wiring one up yesterday, but then my Dryer has now decided not to go hot

found the .zip so that's easy, cheers

[TheCorfiot]

Awesome !!!!!

Any Chance of a close up photo of the coloured wires going to the 20Pin IDC connector on your MMC Interface please, save having to decode The SD signals to User Port Pins...

Thanks Dave

[hoglet]

Any Chance of a close up photo of the coloured wires going to the 20Pin IDC connector on your MMC Interface please, save having to decode The SD signals to User Port Pins...

A picture won't actually help, as the IDC connector is not configured for a Beeb (it's the BeebFPGA one).

Just follow this and you should be OK:

Code: Select all

Electron      SD Card
   2 GND ===> GND   (Black)
   3 PD0 ===> MOSI  (Grey)
   5 PD1 ===> SCLK  (White)
  10 GND ===> CS    (Blue)
  19 ACK <=== MISO  (Purple)
  26 +5V ===> +5V   (Red)

[sirmorris]

I've inherited a Slogger Rombox+. I have to admit that I've never really done any more with it than marvel at the special plastic and its yellowness. Would it happen to be register level compatible with the plus1?

[danielj]

Should be!

[TheCorfiot]

This works very well indeed, very simple but effective hookup

If anyone plans to use SirMorris MMC boards then you can ignore hooking up the blue wire as CS is tied low already on the board

[CMcDougall]

just gave this a go, &

notes:
My 5x eeproms are fine, but this does not work with DaveH's brilliant ATI/ABR cart
Does work with the Pegasus Slogger E00 DFS

[hoglet]

My 5x eeproms are fine, but this does not work with DaveH's brilliant ATI/ABR cart

Col, can you say in what way it doesn't work with the ATI/ABR? Card? error, or some kind of crash before that?

Which flavour MMFS were you using, and how/where was it installed?

DaveH, is there a final schematic for the ATI/ABR posted somewhere? I checked the thread, and there does't seem to be one for the "Issue 2" with the GAL:
viewtopic.php?f=3&t=558

Dave