Serial Cable Lengths

[benjgvps]

I am having some trouble with sending files from my PC to my PowerBook 180c with Stargate (File transfer program). I have checked all the connections on my custom cable yet I still get slower-than-normal speeds and a ton of packets that have to be resent. The cable is quite long, could this be a problem? It was perfectly fine when I had my old computer (etower), could the new components be causing interference?

 

[tomlee59]

Describe your cable a bit more fully. How long? What wire gauge? Shielded? Twisted pair(s)? All of these factors can make a difference. "Too long" really has to be evaluated electrically, not in terms of physical length only.

 

[benjgvps]

It is a standard apple serial cable with about a foot and a half cut off, then joined to a nine pin PC serial cable (Wires wrapped together, covered in electrical tape). They are both shielded but not where they meet in the middle.

 

[porter]

http://en.wikipedia.org/wiki/RS-232

The standard does not define a maximum cable length but instead defines the maximum capacitance that a compliant drive circuit must tolerate. By using low-capacitance cables, full speed communication can be maintained over larger distances. A widely-accepted rule-of-thumb is that for cables longer than 50 feet (15 meters), special effort will be required. For larger distances (hundreds of feet/meters) other standards are better suited to maintain communication speed

What "new components"?

The standard approach with serial comms is to drop the baud rate if you are having problems. Other problems include handshaking mismatch.

 

[benjgvps]

Well this isn't fun. The lowest I can set the baud rate to is 57600... Is there any other good cross platform solution? such as terminal emulators on both ends perhaps?

 

[Charlieman]

When I first read this thread, I thought: RS-422 (the Mac serial standard) should be able to perform over a reasonable distance... The original poster would be all right transferring data at high speed to another Mac or to an old Sun etc assuming quality cables. LocalTalk networking demonstrates how well RS-422 is implemented in the Mac.

But when transferring to a PC, RS-232 limitations apply. Standard serial ports in PCs are RS-232 devices, which operate at lower speeds over shorter cable lengths. 57,600bps is actually a decent speed over the dodgy cable that the original poster describes.

Given that the original poster is using a PB180, locate the PowerBook close to the PC and use a short transfer cable -- although this appears to be the case already. I assume that the OP does not have access to a soldering iron, so ask around for somebody who will help you to construct a better cable. Lab technicians at school/college/company workshop are good people to know. If you are keen and can present a good argument, you'll be surprised how willing they are to help.

Any tips on how to apply home brewed shielding to a heat shrinked solder joint?

 

[equant]

Any tips on how to apply home brewed shielding to a heat shrinked solder joint?

I've repaired coax cables with good success using aluminum foil and heat shrink tubing.

One should be able to find a null modem adapter pretty easily and avoid having to use a hacked cable.

Why is the lowest baud rate 57600? That doesn't make sense to me.

 

[tomlee59]

benjqvps -- you never answered our questions. How long is the cable?? You only told us how much you cut off of each end. That's no help to us at all.

Also, what "new components" are you referring to?

If you really want us to help, please don't assume that we can read minds.

In the interim, can you obtain a short cable?

 

[Charlieman]

I've repaired coax cables with good success using aluminum foil and heat shrink tubing.

I guessed that that would work but I was looking for a smart solution. Shielding sticky tape?

One should be able to find a null modem adapter pretty easily and avoid having to use a hacked cable.

The OP was connecting a PowerBook (8 pin mini DIN) to PC (9 pin D). That sort of cable is hard to find nowadays. Ditto, pin over adapters. (Also a reason why some of us have cabinets full of old cables.)

Why is the lowest baud rate 57600? That doesn't make sense to me.

Possibly the software designer concluded that 57,600 was the lowest worthwhile speed? When you get slow, you are shifting files not directories of stuff. And when you are shifting a few files, why not use XMODEM or ZMODEM?

 

[equant]

The OP was connecting a PowerBook (8 pin mini DIN) to PC (9 pin D). That sort of cable is hard to find nowadays. Ditto, pin over adapters. (Also a reason why some of us have cabinets full of old cables.)

Trust me, I know why we all have cabinets full of old cables.

Tucson isn't a very big city, but I can definitely get db9 and db25 null modem adapters at the one and only electronic parts store in town. It might be worth a look.

Also, I don't really think the presence (or lack) of shielding should be impacting the OP in this situation unless he's in some very harsh rf environment. I agree that ZMODEM is worth trying.

 

[benjgvps]

I made a basic cable from here: http://www.jagshouse.com/modem.html . I have this hooked into the Motorola modem hooked up to the PowerBook and the other end into my iMac G3. I use MacComCenter on the PowerBook and ZTerm on the other. It works okm I have the components taped to my desk and it is fine... though I need to find an altoids tin or something to put the parts into.

EDIT: Well It seems that I don't have to have all those parts in between... I just connected with a plain phone cable... This is MUCH better than stargate, I can bring back the memories of Dial-up Internet! I have a nerdgasm every time I hear the sound of a modem connecting...