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Serial device issues

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Stacey Akerstrom
Frequent Advisor

Serial device issues

For the last 7 months or so, we have been struggling trying to configure a Simplex time clock, a Toledo scale and a Telxon hand-held unit on an A500 running 11i, and an 8 port fan-out mux.
Currently, these are functioning on an NCR 3430 (SVR4), and we are trying to port them over to HP-UX.
Also have a Wyse term and a line printer which we were able to configure.
We cannot seem to communicate to said devices (using homegrown c programs, by the way). I've verified that our ports are good/functional.
At this point, we're not sure if our problem is with the cable pinouts, the c programs, or both. We suspect that the reason the Wyse and printer are working is because they have their own drivers, where we might be writing our own for the other devices.
We have tried virtually every pin-out combination, using both a break-out box and protocol analyzer/break-out box software, and hired two consultants.
We are going nowhere fast, and the deadline on this project is looming.
Would appreciate any hints/ideas.

A. Clay Stephenson
Acclaimed Contributor

Re: Serial device issues

I am all but certain that you are making this much harder than it is; serial connections are generally tedious but not difficult. Because you didn't bother to identify the exact MUX and fan-out cable, it's difficult to be precise. In any event, go to docs.hp.com and enter "Multiplexer Family" as a search string.

One thing to note is that if your fan-out cable is RJ-45, it's probably a 10-pin connector rather than the far more common 8. HP makes an adapter cable that will go from this odd 10-pin RJ45 to a more common DB25P but even in this case the pin-outs on the DB-25 are non-standard. Getting your hands on the Multiplexer Family Cabling documentation is essential.

You will not need an addional driver although you may need to create/use device nodes with the proper minor device numbers. Man 7 termio and pay attention to the section on minor device numbers.

One of my favorite ways to debug this is to use kermit. Edit inittab and make sure that the port in question is set to 'off' and then issue an init q command. Now start kermit and issue a 'set line' command. You can also issue 'set flow', 'set speed', 'set parity', ... and finally issue a 'connect'.

On occasion, I go to another terminal session and do stty commands on the same port that kermit is trying to use.

e.g. stty -crts rtsxoff ctsxon < /dev/ttyd0p3

Once you know what additional commands are needed to use the port, coding any changes is your C application becomes quite simple.

If it ain't broke, I can fix that.

Re: Serial device issues

Hi Stace,

HP commonly uses 8-pin RJ45 connectors for its LAN cables, but when it comes to an EISA or PCI panel, the RJ-45 connectors use a 10-pin configuration. So, pin 1 (on an 8-pin connector) is really pin 2 (on the 10-pin connector).

You'll find the correct pinout for all EISA and PCI connection by going to the following URL:

Hope that helps,

Retired HP