MiST Mod

[Bryce]

Hi,
    here's a mod I'm doing at the moment. I wouldn't usually have posted this here at all, but it's Gryzors MiST, the MiST is becoming more interesting for us since the CPC Core is being developed and I'm not a member of any ST Forum. So here it is...

The general plan looks like this:
- Take MiST out of original case and fit it into an Atari ST external drive. ie: an SF354 in this case.

Goals:
- All connections and power switch on the back.
- SD Card accessable from floppy slit.
- All buttons / LEDs on front, but as discretely as possible.
- Try to keep SF looking as original as possible.

Here's the SF354 before I started:
[attach=2]
(Great cases because they are much more resistant to yellowing than beige coloured ones )

Today I stripped out the insides first. I've installed a "blank PCB" onto the mounting holes of the drive, this allows me to mount things as I want without having to cut holes all over the outer case. This is what it looks like so far:

[attach=3]

The Board is fully coated in copper on the bottom, so I will connect this to GND later to shield the board. Next up I will add another PCB for the new SD slot which will be raised to the height of the floppy slit. Unfortunately, quite a bit of the slit detail is part of the drive and not the casing. So I had to remove this and transfer it to the case.

[attach=4]

For the three buttons I'm going to try to split the original wide eject button into three parts to actuate buttons behind it. Not sure if this will work, but it's worth a try. No plan for the LEDs yet. Suggestions welcome.

Bryce.

[gerald]

No plan for the LEDs yet. Suggestions welcome.

Look there are 3 leds.
One power
One for FPGA
ONe for mass storage access

What about using a RGB led in place of the disk access LED ?

You may need to tune the current limiting resistor (and hope volateg is enough to drive the blue led ?)

[Bryce]

Yes, that's one of the things that I was considering. Unfortunately, the cover for the original LED is dark red, so I can't put an RGB LED behind it
My current idea was to use the original LED position for mass-storage access. Illuminate the complete slot blue for power and FPGA, not sure? Does the user ever really need to see this?

Bryce.

[Gryzor]

Ohhh yeah! Time to get making those decals myself to put on it... Cheers mate!

I just didn't understand what you meant by "Unfortunately, quite a bit of the slit detail is part of the drive and not the casing. So I had to remove this and transfer it to the case."?

As for the LEDs, ah we had discussed this and you had told me about the RGB LED but not about the cover being red... Too bad, but the other solutions sound cooler All three LEDs are useful to diagnose what's going on - well, the power LED is not more useful than other power LEDs, but if you did that whole-slot illumination it would look utterly cool...


Really nice solution, mounting a blank PCB at the bottom

[Bryce]

I just didn't understand what you meant by "Unfortunately, quite a bit of the slit detail is part of the drive and not the casing. So I had to remove this and transfer it to the case."?

If you look at the last picture in the first thread. That big plastic bit in the middle was part of the drive, not the case. I had to remove it from the drive and now need to find a way to connect it to the outer case.

LEDs: New idea. Storage LED is the drive LED. Power LED makes the slot glow blue, but FPGA LED changes the glow to a different colour?

Bryce.

[Gryzor]

Oh, I see. Why not just a couple of drops of glue? Or am I missing some implication?

Yup, good idea about the LEDs, especially since it means you won't have to drill another hole that will necessarily be different than the existing one Only negative I can think of is if the LED is not powerful enough...

[Bryce]

Oh, I see. Why not just a couple of drops of glue? Or am I missing some implication?

Yup, good idea about the LEDs, especially since it means you won't have to drill another hole that will necessarily be different than the existing one Only negative I can think of is if the LED is not powerful enough...

Yes, I can just glue it, it was just the hassle of having to dismantle the drive etc that I was moaning about

I have some plexiglas light-pipes that I will experiment with and see how much light I can get. I am thinking of having a plexiglas tube across the slot with a blue LED at one end and a red LED at the other end. That way it would glow blue but turn red on FPGA activity. I want it to look cool.

Bryce.

P.s. I've decided to buy one of these to extend the SD card slot: SD card extension Cable PRICE INCLUDES VAT | eBay . My first plan was to remove the original slot and put it on a new PCB. I'd prefer not to modify the MiST PCB at all for warranty/repair reasons, but the buttons/LEDs don't have a header, so some modification is unavoidable. I'm not that happy with the length of the extension (SDcard connections should be kept to a minimum), so I will shorten it to the required length.

[Gryzor]

Of *course* it must look cool! Maybe we can get some sound feedback and have them light up in rythm, a-la Chinese gadgets

Ah, the extension then, hope it works. If it does it's a great solution indeed... Do you plan on filling the space around the SD slot in any way?

[Bryce]

Just realised that the extension probably won't work. It doesn't pass on the "Card inserted" signals, so the MiST would always think a card was inserted which might mess up the software. Looks like I'm back to removing the original slot.

If the light-pipe works, then there will be clear plexiglas filling the rest of the slot. Otherwise I will fill it with black plastic.

Bryce.

[Gryzor]

Not sure the board actually does anything with the signal, and in any case I don't ever turn it on without a card in it so I'm unsure as to how much of a problem that would be... Do you want me to ask the dev anything specific?

Ps ew, black plastic

[Bryce]

Black matt plastic, but deep inside, just so that you don't see inside it.

I'll take a look at the PCB tonight and see if the card-present signals are being used. If not, I'll order the extension.

Bryce.

[Gryzor]

Ah, deep, that's better

Ok, crossing fingers

[Bryce]

Looks like the MiST uses the card-present signals, they are definitely wired back to the FPGA. I think it's better if I extend the socket from the PCB.

Bryce.

[Gryzor]

Hm. But, what problems could that present? As I said, you can't run it without a card present, so even if software gets confused or whatever, what's the harm?

[gerald]

I would second Gryzor opinion.
1st  -  the FPGA core is on the SD card, so there is no point starting the MiST without it.
2nd -  the software should detect that there is no card anyway by timeout when initialising the communication to the card

[Bryce]

True, maybe I'll order one of those extension cards and give it a go. I wasn't aware that hot-swapping isn't really possible anyway.

Bryce.

Edit: Extension card ordered.

[Gryzor]

(Sao Tome and Principe's power supply might be more of a problem to the unit than an absent SD card )

Not only is hot-swapping not really possible, but it's without any merit either; you've got a huge card containing everything, only reason you'd swap it is if you downloaded something and wanted to load it after powering up the unit... So I guess all's well with it (assuming it works!).


By the way, how are you planning to extend the VGA and USB after all?

[Bryce]

Ahhh, I have my own Cocoa bean powered generator here on the island

I have panel mounting USB and VGA sockets that will be mounted on the rear and have small extension cables that plug directly into the original sockets. For the power I intend to add the same socket as the CPC 5V uses. That way you can power the MiST using your CPC PSU.

Bryce.

[Gryzor]

Sounds very cool The cocoa-bean-powered generator, I mean.

[Gryzor]

Just to make sure I asked Till, his reply was he can see no problem with always telling the board a card is present

[Bryce]

Thanks. As soon as the extension arrives I'll have a try. I still haven't powered it up even once?  I'm afraid I would waste days on it

Bryce.

[Gryzor]

Ah, but that's a shame really... You should probably do some thorough "testing" once it's done!

(but hey, how do you know it even works? )

[Bryce]

I don't at the moment, but I will fully test it before a soldering iron ever touches it. I always do.

Bryce.

[Gryzor]

Ah, there goes the modding

[Bryce]

Still waiting for the SD Card thingy to arrive, so I thought I'd start on the back of the case where I intend mounting (if possible) all ports. As you can see, at the moment it has the regular ST round connectors (in/out) etc, so this all has to go. There's a ridge that I thought might be useful for holding the new back panel, but it's only 2mm deep and the plastic I have is 3mm thick, so that has to go too.

[attach=2]

[attach=3]

Then I cut a piece of plastic to fill the space. I'll secure this with two screws through the back when it's finished.

[attach=4]

Now time to make the hole. It's just roughly cut at the moment as I might need to make it bigger depending on the space I need for the connectors.

[attach=5]

And here it is with the panel fitted.

[attach=6]

The plastic isn't exactly the same colour, but it's at the back and will be filled with ports anyway, so it's not a big problem. At this stage I realised that other than the USB and VGA ports I don't have the others, so I'll need to order those now. The SD card will probably arrive in the meantime, so I can start on that while I'm waiting for them to arrive...

Bryce.