PC floppy adaptor for Amiga

[prowler]

Hi All,

The first thing I did this evening was completely strip my Escom A1200 apart to get to the underside of the motherboard and check for a link between pin 34 of the internal floppy connector to pin 1 of the external connector. There was none. I have an unmodified Rev 2B motherboard.

Once I was certain about that, it meant I didn't have to check the Panasonic drive, as it would play no part in the test.

I had already downloaded and decompressed the Sanity Arte and State of the Art demos. When I checked them on WinUAE emulating an A1200 with 2MB chip RAM only (which is all my Escom has ATM), Sanity Arte ran fine, but State of the Art straightaway crashed the emulated machine. I assume that State of the Art requires some fast RAM. Nevertheless, I prepared both Sanity Arte and State of the Art floppies to use for the testing.

I replaced the Panasonic drive in the Amiga with the Mitsumi PC drive and adaptor combination, again using the external 5V supply. The clip I attached to a paper clip inserted in pin 1 of the external floppy drive connector. I didn't require the external floppy drive for this test, because I have already verified that the adapter successfully converts a PC floppy drive for use in external configuration, and both demo disks require booting in any case.

I switched on the Amiga to check that the disk drive was operating correctly, inserted the Sanity Arte disk and rebooted the machine. The demo started up and played right through without a hitch, before auto-rebooting and starting up again. At this point, I disconnected the clip from the external drive socket and rebooted once more.

The floppy disk booted up, but produced only a cyan screen, although the disk continued to spin. When I reconnected the clip, the demo started up instantly!

When I tried the State of the Art demo, it ran for a few seconds with a the image of a hand with splayed fingers moving about on the screen, before giving a Guru software error! This is further than it got in WinUAE, but I don't think it will run with just 2MB chip RAM. Aminet doesn't mention the memory requirement.


I think this test confirms that Stedy's adapter works just as well in an unmodified Escom A1200 than it does in more 'compatible' Amigas.

Thanks to Stedy and others for your help with this. If anyone has any questions, feel free to ask. I will be pleased to try and provide the answers.

prowler

PS. I was wrong previously about the adapter suppressing the clicking which accompanies the disk sensing activity. In fact, it does not. The internal and external drives in close proximity for the initial tests must have made it difficult to resolve two clicks.

[prowler]

Originally Posted by Yotoxionomai

I´ve been following this thread with some interest for some time now, and wondering if this adapter could be changed to work with the external drive port.
If some kind of adapter DB23 to IDE 34 could be fitted, could it be used externally instead?

Hi Yotoxionomai,

I have tested the adapter externally by fitting it between the interface board of a Cumana external floppy drive and the Mitsumi PC floppy drive, and it worked flawlessly.

The problem with this is that the interface board has a couple of chips and a few capactors on it, so Stedy's adapter is not actually connected directly between the PC floppy drive and the Amiga's external drive port in this configuration.

The interface board / floppy disk drive assembly (without Stedy's adapter)is shown in this post:
http://eab.abime.net/showpost.php?p=513373&postcount=23
if you wish to take a look.

There is also a pass-through connector on the rear of the floppy drive enclosure, which allows connecting further external floppy drives DF2: and DF3: in a chain, and one function of the interface electronics is probably to make sure that floppy drives connected further down the chain are correctly addressed.

If you did not wish to connect more than one external floppy drive to the Amiga, then I would think that Stedy's adapter could indeed be used on the external port, with a correctly wired 23-way D-type to IDE34 adapter.

prowler

PS. The Amiga will supply power only to the first floppy drive on the chain. There is no power available at the pass-through connector on the rear of the Cumana external floppy drive enclosure. The second and third drives fitted to the chain must be supplied from a separate power source.

[Jope]

Originally Posted by prowler

PS. The Amiga will supply power only to the first floppy drive on the chain. There is no power available at the pass-through connector on the rear of the Cumana external floppy drive enclosure. The second and third drives fitted to the chain must be supplied from a separate power source.

That is a feature of your Cumana, but you can't generalize it to apply to all external drives. Seems like they adhered to commodore's A500 specifications to the letter.

Most Amiga external drives will pass through the voltages just fine.

[prowler]

Originally Posted by Yotoxionomai

I´ve been following this thread with some interest for some time now, and wondering if this adapter could be changed to work with the external drive port.
If some kind of adapter DB23 to IDE 34 could be fitted, could it be used externally instead?

Hi Yotoxionomai,

If I can put together a suitable DB23 to IDE34 adapter, then I suppose I could check whether or not Stedy's existing design is compatible with the external drive port.

It should also be possible to derive a circuit diagram for the Cumana's interface board from the layout, which will tell us whether it provides functions other than discriminating the drive from others connected to the chain.

Originally Posted by Jope

That is a feature of your Cumana, but you can't generalize it to apply to all external drives. Seems like they adhered to commodore's A500 specifications to the letter.

Most Amiga external drives will pass through the voltages just fine.

Hi Jope,

I am not certain that the Cumana has this 'feature'. I acquired this drive second-hand without a user manual. I had just assumed that manufacturers of external disk drives for the Amiga would have complied fully with Commodore's specifications.

In any case, I wouldn't like to take the chance that my Amiga could supply two or more external drives without damage to the motherboard printed circuit, and I would warn others not to do so either.

@Stedy:

Do you wish me to return this adapter, or would you prefer me to keep it as one of the two I had originally wished to order?

If I should keep it, I could order and pay for two using your online ordering system, and then you can send me just the other one. How does that sound?

As I live locally, couldn't I bypass the online ordering system and save you the cost of postage?

PM me.

prowler

[Jope]

Originally Posted by prowler

In any case, I wouldn't like to take the chance that my Amiga could supply two or more external drives without damage to the motherboard printed circuit, and I would warn others not to do so either.

Well. Maybe it will run out of juice if you chain more than one A1010, but an A500 will easily drive three external 3rd party slimline drives.

We all did it in the 90s, X-Copy and then later SuperDuper chugged away at our computer club meetings with stacks of floppies and drives on top of the machines.

[Yoto]

Hi Yotoxionomai,

If I can put together a suitable DB23 to IDE34 adapter, then I suppose I could check whether or not Stedy's existing design is compatible with the external drive port.

It should also be possible to derive a circuit diagram for the Cumana's interface board from the layout, which will tell us whether it provides functions other than discriminating the drive from others connected to the chain.

That would be so nice prowler, i would really like to use something like that!

[Stedy]

Hi,

I've been a bit busy. The user and assembly manuals should be online this weekend. Just need to proofread before I PDF them.

@Prowler

You can keep that unit as one of the two you requested. I'm sure we can bypass the payment system

@Thread

I have contacted Westfield connectors about availability of 23 way d-subs, waiting to hear back from them. This could help with external drives and I need some connectors for a video device I'm working on.

Have also done some experiments to see if I can make an HD adaptor but not had much success so far. Pin 2 of the PC floppy drive is the density select pin, normally an input but on some drives it can be an output. Well on the 3 drives I have tested so far, it is not used The only way to detect HD/DD is to wire onto the switch inside the drive, not elegant. Will keep investigating.

I would like to start a list of drives used with my adapter so when you receive your orders, could you add any details to this thread.

I have tested these drives so far:
Alps DFE354H090F
Epson SMD300
Mitsumi FA404M (FDD portion only).

Time for dinner.


Ian

[prowler]

Originally Posted by Yotoxionomai

That would be so nice prowler, i would really like to use something like that!

Hi Yotoxionomai,

Thanks for the encouraging response, mate!

I'll get to work on it while I've still got all the bits out on the bench.

Originally Posted by Stedy

@Prowler

You can keep that unit as one of the two you requested. I'm sure we can bypass the payment system

Thanks, Ian. I'll be in contact with you soon.

Originally Posted by Stedy

Have also done some experiments to see if I can make an HD adaptor but not had much success so far. Pin 2 of the PC floppy drive is the density select pin, normally an input but on some drives it can be an output. Well on the 3 drives I have tested so far, it is not used The only way to detect HD/DD is to wire onto the switch inside the drive, not elegant. Will keep investigating.

I have some information on using HD PC floppy drives as HD Amiga floppy drives. I'll upload some scans for you if I can find the articles.

Originally Posted by Stedy

I would like to start a list of drives used with my adapter so when you receive your orders, could you add any details to this thread.

I have tested these drives so far:
Alps DFE354H090F
Epson SMD300
Mitsumi FA404M (FDD portion only).

You can add my Mitsumi D359T5 floppy drive to that list!

prowler

[Eclipse]

I think the only other option you have for density select would be a switch.

[prowler]

Originally Posted by Eclipse

I think the only other option you have for density select would be a switch.

Hi Eclipse,

Yes, a switch or even a jumper. That would be an easier solution and not too much of an inconvenience for the end-user.

prowler

[Stedy]

Hi,

The user manual is now online,http://www.ianstedman.co.uk/download...ser_manual.pdf 271K PDF and the assembly/build manual is also online, http://www.ianstedman.co.uk/download...ild_manual.pdf 804K PDF.

Feedback appreciated.

Ian

[prowler]

Thanks, Ian!

Will let you know what I think.

prowler

[prowler]

Hi Ian,

I've studied the PDF manuals you uploaded and I've found only one mistake in the User Manual on Page 3.

The JP1 2-3 header suggests that this is the normal position for the jumper, and this is correct.

However, in the text which accompanies it, the 1-2 and 2-3 jumper positions are wrongly described.

Apart from that, everything's OK!

prowler

[Stedy]

@Prowler

Thanks for reviewing the document. I have corrected the document and uploaded V1.1 to my website.

@Thread

An updated PCB design will only be considered once I have sold the first batch, I still have 35 PCBs/units to sell.

Support for DF1 without a cable twist and possibly an option for a DB23 connector are possibilities.

I like the idea of a switch/button to select High density disk support. This will be a separate project though. The logic device needed costs 2.5x the price of the logic device used in the current design (£0.68 versus £1.68) and I need to build/buy a PAL programmer so there new unit, if successful, will cost more.

Thanks to the testing by Prowler, the Escom fix has been validated so if you want to use this unit to replace a drive in an Escom/AT A1200 please order when ready.

Bye,

Ian

[prowler]

Originally Posted by Stedy

@Prowler

Thanks for reviewing the document. I have corrected the document and uploaded V1.1 to my website.

Hey, that was quick! Great work.

Originally Posted by Stedy

An updated PCB design will only be considered once I have sold the first batch, I still have 35 PCBs/units to sell.

Can I have one of those, please, Ian? I'll speak to you soon.

Originally Posted by Stedy

Support for DF1 without a cable twist and possibly an option for a DB23 connector are possibilities.

I'd like a couple of those too, please, when they appear.

Originally Posted by Stedy

I like the idea of a switch/button to select High density disk support. This will be a separate project though. The logic device needed costs 2.5x the price of the logic device used in the current design (£0.68 versus £1.68) and I need to build/buy a PAL programmer so there new unit, if successful, will cost more.

I'll gladly pay whatever it costs to get one of these!

Thanks very much for all your effort, Ian!

prowler

[AlfaRomeo]

Hi ppl,
My PC floppy adaptor arrived yesterday, it´s the #4
Thanks for your great work Ian

[prowler]

Originally Posted by AlfaRomeo

...it´s the #4

Hi Alfa,

Do you mean it's connected to the 4th floppy drive on your machine?

prowler

[kipper2k]

Hi Ian,


Do the plastic tabs on the floppy drive have to be broke in order for the power connector to be able to fit. I have about 4 different type of Floppy drives and the connector will not fit on any ?.

edit: nm, i broke the tabs off so it would fit on the floppy 4 pin header.

Originally Posted by Stedy

Hello,

I've finally started assembly.

Thought you might like a few pictures of the first assembled unit. Sorry if a little blurry, used my camera phone.

The assembled PCB.



Underside of PCB.



Connected to a disk drive.



There are two sets of jumpers.
The first changes the drive select signal on the PC drive to allow DS0 or DS1, this caters for drives/cable settings.

The second jumper allows the nREADY signal to either be output via pin 34 to the Amiga or using a cable connected to the 23 pin d-type for Escom A1200s.
The user manual, which I have yet to write will detail this.

A support page will go online soon. Schematics, PCB layout and bill of materials will be available.

Pricing and orders

I want to get a number of units assembled before the new ordering system is put online, please bear with me.

An assembled unit is 9 UKP
A kit of parts is 6.50 UKP
A PCB is 3.50 UKP

Currently have the parts to make 50 units in stock. Have had expressions of interest covering 26 units so far, so there are units available for ordering.

Dinner time

[Calgor]

@Stedy

If it is the case that the connector on floppy drive must be broken for most floppy drives, shouldn't a normal floppy connector be used? The one in the picture does not look like the standard one which has part of the back of the plastic indented to make it slimmer (and therefore I imagine it would then fit the floppy's connector without any mods).

[cosmicfrog]

now i look at that power connector I see that it is indeed not a floppy power connector, more of a motherboard fan conector

still bending the plastic at the back of the pins should allow you to use it without any problems.

Niggles aside Ian lovein the work