Hi folks --
I'm attempting to get my old IIGS (ROM01) system back up and running but am having an odd issue.
I have what I *think* is a null modem cable going from the IIGS' modem port to a serial-to-USB adapter on my OSX Mac. To be precise, I have a IIGS modem cable connected to a LapLink serial cable (which I've used as a null modem cable previously in other contexts), which itself then connects to the serial/USB adapter.
When I run ProTERM on the IIGS and zTerm on the Mac, I am able to type back and forth between the two machines. I am also able to send files from the IIGS to the Mac via Zmodem and other protocols with zero problems.
The weird part is that Zmodem transfers in the opposite direction -- from the Mac to the IIGS -- fail consistently (and quickly) with "data mismatch" errors. I have spent hours trying every combination of settings in the IIGS control panel, as well as in zTerm. I've also tried Xmodem, Ymodem, and even freakin Kermit. 
Uploads from the IIGS always work, but downloads to the IIGS always fail.
On a possibly related note, I tried using ADTPro to bootstrap the IIGS, but it never receives any data during the bootstrapping process.
So my question is: do these symptoms sound like a bad or incorrect cable? Or could this be due to a deeper issue, like a hardware problem on my IIGS?
Thanks for any advice!
--Stephen
There's the problem right here. LapLink isn't quite right for this context. It's got some incorrect wiring going on.
Yep, I've seen that before.
Yes. Take a look at the ADTPro site and wire one up like that.
OK, thanks for the quick and definitive answer! could SWEAR that I had luck with this same set up a few years ago, but perhaps I am going senile. I will seek out or build the proper cable and try this again. Thanks!
If I discard the LapLink cable, I'm left with a IIGS modem cable (mini-DIN to DB25). If I added a null modem adapter, followed by a DB-25 to DB-9 adapter, seems like that would do the trick? Just trying to see if I can leverage more easily available parts.
Thanks again!
Yep, that would work (assuming your cable is really the Modem variety/straight through). I show that exact setup on the ADTPro serial connections page... many layers of adaptation is fine, as long as the two ends end up putting the pins in the right place. The trick can sometimes be knowing exactly what your cables and adapters really have inside them.
So I went ahead and purchased a IIGS null modem cable from RetroFloppy (well-made product, fast shipping!). But to my surprise and dismay I am still having trouble.
When trying to send files from the Mac to the IIGS (using Zmodem, ProTerm on the IIGS, and zTerm on the Mac) I am still unable to complete a file transfer. I get a "checksum error" followed by continual "data mismatch" errors until the transfer fails. Note that I can send files in the opposite direction, from the IIGS to the Mac, just like before. I have tried every combination of baud rate, buffering, XON/OFF, hardware handshaking, and both terminal and Zmodem settings in zTerm -- no change.
Interestingly, on the ADTPro side of things, I am now able to get it to send bootstrapping code and I can see it scrolling by on the IIGS screen. However, there are frequent "SYNTAX ERROR" messages -- it almost looks like characters are being dropped. It doesn't end up working.
Could I have a bad serial port on my IIGS? Seems unlikely? BTW this is a Woz edition that reports "ROM Version 01".
Another idea: is it possible my USB-to-Serial adapter is bogus? I'm using an IOGear GUC232A.
Thanks for any advice! Super frustrating.
--Stephen
Even if you slow the baud rate way down... you still can't get an error-free bootstrap?
Probably not. I had a bad serial port on my first GS, and it simply didn't work at all.
That's sounding like a good possibility at this point. Do you have any other hardware you can test with - like an old PC that has a built-in serial port?
Nope, I've tried all the way down to 1200, no luck.
That's a good idea. I don't have any extra hardware but I can probably borrow from a friend. I may also go get a different model of serial-to-USB adapter and test that too.
Thanks for the advice.
So I tried a PC laptop and it worked fine. I also tried out my serial-USB adapter on a different Mac and had the same problem. So it definitely the adapter.
After trying several models, I would warn Mac users away from using either Belkin or IOGear models. They don't work, at least in this context!
So far I am having better results with a GearHead CA2000 model. I still get random errors from time to time, but at least now I can complete a successful file transfer via zmodem. Interestingly, when trying to use ADT Pro bootstrapping, data does stream by but I get at least one error on each transmission, and the result is that I can't get ADT Pro to work.
So, some progress I guess. Wanted to pass this along in case others are considering buying a serial-to-USB adapter. Avoid Belkin and IOGear!