IR fails after moving it to Thinkpad - cable worked b4 on PC

donphillipe · Post by **donphillipe** » Tue Jan 20, 2004 9:16 pm

I just copied all my IR and Keymaster Directories from my desktop PC to my Thinkpad T30. (I need to make the 1 hour drive to my Moms to work on a remote that won't properly control one of their devices that I previously programmed in.) The JP1 cable that I have been using recently, I had bought about 1.5 years ago from someone off hifi-remotes and it has been working great on my PC. I unplugged it from my PC parallel port, plugged it into my Thinkpad and it won't work on my Thinkpad now? It does work when I move it back to the PC.

Using XP on the both the Thinkpad/desktopPC. I opened the Thinkpad device manger and find on this machine IO port being used is different (03BC) so I thought I had found the problem and I changed the IR Parallel setting, but it still fails with "Did not receive a response ...".

I tried unchecking autocheck because someone else wrote they had a Thinkpad and they found that unchecking this allowed it to download even though an error displays. This did not fix my problem. Is this possibly a cable design problem? I see a lot of discussion on diodes and resistors and I know the difference and can test if I knew what was supposed to be inside the cable I bought and where the "builder" of my cable put one/them (assuming they even installed either way back then).

Where do I go from here? Any idea where to start with debugging this problem?

gjarboni · Post by **gjarboni** » Tue Jan 20, 2004 9:29 pm

A common problem in laptop parallel ports is that Ground is not always on Pin 25. Connecting pins 25-18 (by soldering a paper clip over them) is a good way to adjust your interface if this is the problem.

Post by **The Robman** » Tue Jan 20, 2004 11:13 pm

If your cable is old, it may well have been built using a regular signal diode, rather that the Schottky diode which is now standard. Plus, it may well use 10k resistors instead of the 1k resistors which are now standard. Plus, there's also the possibility that pins 18 to 25 are not tied together, as Jason suggested.

All of these revisions to the design were done with Laptops in mind.

If you open up your cable, you can check for these things:
1) is there a pin or wire joining pins 18 to 25 together
2) is the diode small and reddish in color, or black with a grey stripe and somewhat thicker.
3) I forget the color stripes off the top of my head for resistors, but if you post what you have we can verify if they are 10k or 1k.

The easiest solution might well be to just get a new cable for your laptop.

donphillipe · Post by **donphillipe** » Wed Jan 21, 2004 12:37 am

You got it right, I'll head to RS and get a load of replacment parts. I disassembled it and see I have 10K instead of 1K, the old style diode, plus the jumper 25 to 18 you suggest is missing. At least I can use the old cables & connectors.

Wish I had asked about 6 hrs ago, another simple task bites the dust for me, but THANKS for stopping me at 6hrs

I'll let you know the outcome (just thought buying a ready made model would let the iron stay in the closet!).

TimH · Post by **TimH** » Wed Jan 21, 2004 5:36 am

If I was you, I'd build a whole new cable based on the new specs to carry in the laptop, and leave the old cable with the pc where it's always worked. Either way I'd avoid trying to desolder the db25 to reuse it. The cost of a db25 is way less than the time, effort, and frustation of a cable that doesn't work due to a mangled db25. Plus you already gotta make a trip, so why not spring for the extra couple bucks for another db25 and hood.

donphillipe · Post by **donphillipe** » Wed Jan 21, 2004 9:46 am

I ordered the parts from Mouser but went ahead (before I saw the last post) and soldered in the jumper from 18-25. I still got the error on the Thinkpad but I turned off the Autocheck and I can now upload and download with no problem.

I will probably build 2 cables as suggested, one for home and one for "the road", especially since my friends see what I can now make Universal remotes truly universal!

THANKS JP1 GROUP!!!!!

I guess one day soon I will have to tackle macros. Too much punching around to select inputs - but since it took me a year to force myself to learn normal JP1 programming - macros may not be all that soon!