ISA to USB - Are these anywhere to be found?

[DaCiRo]

I have been looking for an ISA to USB 8bit card for my IBM XT (see picture below). At some point these cards seemed to be around and Lo-Tech had stock (out of stock since I don't know when).
Now the only places I found that these cards seemed to be heavily commented and reviewed are on some Chinese vintage computer sites and their info (translated) is great, But aren't these cards no longer in the circuit of Western Vintage Computing at all? Any one knows where might find the parts or a kit of an assembled one?

 

[Malc]

The lo-tech isa-usb cards were experimental but didn't get very far unfortunately, The chinese isa-usb cards were available on aliexpress and a few members bought from them IIRC, There is a couple of threads on here somewhere.

 

[DaCiRo]

I see. Thanks Malc. I found a seller from China that has some available. I will post more on this when it arrives.

 

[Malc]

Yes, Please post back when it arrives and let us know how you get on, Are you getting the Boot Rom with it ?.

 

[DaCiRo]

Looking at old post and making updates. The card never arrived, Seller in Taobao asked me to pay extra for shipping where I live, and again pay gain for a Cd with drivers… then he claimed that could not be sent out because of export restrictions and never replied again any of my messages… complete scam.

 

[Malc]

Unfortunately Lo-Tech never finished the R2 ISA-USB card they started, Why i dunno, The only ones i know of are from Chinese sellers on ebay, I wouldn't buy one of them.

 

[cjs]

So you're looking for a USB host interface that you can plug into an ISA bus? Or did you want it to work the other way around, with the ISA board acting as a client (e.g., providing a serial or USB FIFO interface used by another machine acting as the host)?

I'm feeling that the easiest way to go for the former might be to use a modern microcontroller that can act as a USB host, and program it to provide some sort of API on the ISA bus for whatever you want to connect to. (This could be as simple as just talking to USB HID devices, or as complex as providing a full USB host stack.)

 

[Timo W.]

Unfortunately Lo-Tech never finished the R2 ISA-USB card they started, Why i dunno, The only ones i know of are from Chinese sellers on ebay, I wouldn't buy one of them.

It's completely documented:

Lo-tech ISA USB Adapter - Lo-tech Wiki

www.lo-tech.co.uk

So it should not be hard to build one - all info is there. But given that these are not full USB host controllers anyway and only work as storage, I have trouble understanding the need for one. Simply use an XT-IDE card with CF.

If you are looking for a way to e.g. connect USB mouse and keyboard, there are external adapters.

 

[Malc]

It's completely documented:

I know it is, That is the first 'Experimental' design, I have got one of those, Had it since lo-tech sold the PCB's years ago. It works.

So it should not be hard to build one

That has been on my to try list for a long time.

I have trouble understanding the need for one. Simply use an XT-IDE card with CF.

I like using flash drives, I can also use SD / CF cards in a USB adapter, Flash drives / SD Cards are cheaper than CF.
I have had XT-IDE cards with CF since the beginning, I use an XT-IDE with CF and my ISA-USB card with Flash drive in my XT, I can 'hot swap' the USB drive as needed, I can't 'hot swap' the CF in the XT-IDE.

If you are looking for a way to e.g. connect USB mouse and keyboard, there are external adapters.

I have zero interest in using USB mouse or keyboard, I'm only interested in storage.

 

[Hak Foo]

I had no problems with one bought off of AliExpress. You need to cut and jumper a few wires if you want to use it with the "16-bit wide port" mode and appropriately configured software for a marginal performance boost. See this post https://forum.vcfed.org/index.php?threads/isa-usb-board.76978/post-1273514

Malc, I'm wondering what you meant by "hot swap"?

If you interpret it as "unplug the drive and put a new one in while the PC is on", I'm curious what software you're using.

The BIOS I worked on for the CH375 cards is NOT hot-swap capable. It never advertises the drive having changed. (Hell, the CH375 itself doesn't provide an obvious way to know it changed). So if you pull one drive out and plug another in with that BIOS, it does horrible things (garbage directory listings at least, didn't dare try to load or write anything)

I also did a few quick experiments, and re-running the BIOS initialization or INT 13 function 0 (disc reset), or advertising the drive changed on any INT 13 function 16 check didn't help; I assume stuff like LS-120 and SyQuest drives did additional things to tell DOS they were removable.

OTOH, if it's just "the plug is on the back of the PC so I can power off and replace it more easily than a CF card inside the case", I can get it entirely. I do the same thing.

 

[Chuck(G)]

Bit 7 in word 0 of the return from the 0xec IDENTIFY DRIVE command if set, indicates that the medium is removable. Just that simple. Windows XP and later looks at this bit and refuses to install the swap file on a removable device; it can also refuse to install XP on the same device. Fortunately, there's a device driver "wedge" that masks this flag.

 

[Hak Foo]

I think that's at a different level. 0xEC as IDENTIFY DRIVE seems to be an IDE/ATA command, not something we can really present when it's a completely non-IDE device.

 

[Malc]

I had no problems with one bought off of AliExpress. You need to cut and jumper a few wires if you want to use it with the "16-bit wide port" mode and appropriately configured software for a marginal performance boost. See this post

There seem's to be 2 or 3 different versions of the Chinese ISA-USB card floating around, I know the boot rom socket didn't work in some from previous post's, Cutting and jumpering wires and adding an IC to make the card do what it should is not worth the hassle, It's too expensive for that crap.

Malc, I'm wondering what you meant by "hot swap"?

I know your BIOS is not hot-swap capable, What i meant was using FreddyV's Dos driver one can swap out the USB drive with the PC running, No need to switch off or Re-boot.

I see you have updated your BIOS recently, I will update the boot rom in my card when i can. Your BIOS is very useful.

 

[new_castle_j]

So I got this PC-104 to USB card with the CH375 chip in hopes that I could plug it into the PC-104 expansion slot on a modern ISA SBC that I have. There's scarce documentation on this card, I assume that it would work the same way as the ISA-to-USB card, but I have not been able to figure it out. There's no jumpers on the PC-104 board to set an I/O port, I assume that the ATF16V8B-15PU – 16V8 Programmable Logic Device is what handles the I/O addressing. I've used I/O port scanning software in DOS to attempt to probe for it, but found nothing. Could this be some kind of PnP board? I'm not sure what to try next, anyone have an idea?

 

[Eudimorphodon]

There's no jumpers on the PC-104 board to set an I/O port, I assume that the ATF16V8B-15PU – 16V8 Programmable Logic Device is what handles the I/O addressing. I've used I/O port scanning software in DOS to attempt to probe for it, but found nothing. Could this be some kind of PnP board? I'm not sure what to try next, anyone have an idea?

I'll confess I don't know enough about ISA PnP to make anything but a Wild-A**-Guess, but it seems a little suspicious to me that the other chip on this card is a 74HCT273 latch. It is certainly possible that the driver for this thing does something like storing an value into that latch via a blind write to a configuration port that activates and enables the actual storage chip on some range of possible addresses. Not sure *why* you'd do it that way since the 375 only occupies two ports, but... ?

 

[cjs]

The latch, from its positioning and what I can see of the traces near it, looks as if it's likely latching data for the data pins of the CH375.

Anyway, unless you can dump the 16V8, my only idea is to set the thing up on a test rig (or maybe just use a 'scope while it's on your computer) and start going through all the ports poking at it until you see a select signal coming out the other side to select the '273 and/or the the CH375, or the CH375 A0 line changing.

Though, just to check, the write-only command port appears to be A0=1, and the read/write data port appears to be A0=0. Were you writing a $01 to each port in your address space and then attempting to read the port address one less than that to see the version come back? (And I guess the port address one more, as well, just in case the designers had decided to reverse the two.)

BTW, the CH375 datasheet is fascinating. I really love the writing style, with its "public grounds" and "feeble pull-up resistor," "reset[ting] it credibly," and so on.

 

[Eudimorphodon]

The latch, from its positioning and what I can see of the traces near it, looks as if it's likely latching data for the data pins of the CH375.

The '273 is sitting astride traces from what looks like the data pins from the bus and we can't see with the chip and socket in place quite what's going on under there. It would be a pretty normal thing to do if the latch is there to grab a byte from the bus and latch it (for either GAL and/or the CH375 to consume) to run the data bus to the "D" pins on the '273 and from there branch off the data bus to the '273 sitting above it. You see this on PCBs all the time. (Data busses hopping from device to device to device.)

If the CH375 were sitting on the Q pins of the '273 that raises the difficult question of how data would get from the CH375 back to the bus. The '273 is not bidirectional and if the data pins of CH375 were connected on both sides of the '273 then the '273 would *also* be driving the ISA bus whenever it was driving the CH375. Kind of hard to picture how that would ever be a good idea. If you *really* needed a buffer to stretch writes or whatever for the CH375 then you would need to have a separate latch or buffer for the opposite direction.

 

[Eudimorphodon]

Hahaha. Okay, so... wanna see something wild? Here's a picture of what looks like a very identical PC-104 USB card from a listing on AliExpress:



Has a GAL, the CH375B... but instead of a 74HCT273 it has a 74LS245. Which is a bidirectional buffer, something that makes *waaaay* more sense without invoking some weird PNP theory.

@new_castle_j - is your card definitely as-delivered from wherever you bought it from? You don't happen to have a link to the listing, do you? A link with a picture? If there's supposed to be a '245 there and they populated it with a '273 that would definitely be an issue.

 

[new_castle_j]

Wow, what a fascinating picture! I purchased my card off of Ebay, probably 2 years ago. The listing is still up though:

1X PC104 to USB PC104 interface to U disk interface for industrial computer | eBay

The driver only works when the application program reads and writes the U disk. It supports hot plugging and unplugging of U disk, which is convenient to use. and the U disk can be plugged in only when needed.

www.ebay.com

It's definitely worth going through my IC drawer and seeing if I have a spare 74LS245... that's some fine detective work there! If replacing that chip works, I will be chuckling at the "OK" quality control sticker that's on my board.

 

[Chuck(G)]

No kidding! The 273 is noted for its odd interweaving of input and output pins, while the 245 is a straight-through transceiver. More up-to-date designs use the 573, which, has inputs on one side and outputs on the other. Much simpler when laying out PCBs. There's no way a 273 could substitute for a 245.