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USB to Serial lead problem

Discussion in 'Hardware' started by philbenson, Dec 9, 2008.

  1. philbenson

    philbenson Byte Poster

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    This problem requires some explanation so please bare with me...

    A friend and I both have LX200GPS telescopes which support twin RS232 ports for connection to PCs or laptops. The method I have always used is to use first an RJ11 to 9 pin serial lead, and then a 9 pin serial to USB converter lead and then plug this into a free port on the laptop. I then use ASCOM (http://ascom-standards.org/Downloads/ScopeDrivers.htm) to establish communication between laptop and telescope. The serial to USB converter lead is then allocated to a free COM port and I then configure ASCOM to use the same port number. So far so good.

    So he could do the same, my friend bought a USB to serial lead like mine, connected everything up but failed to make a connection with his scope. I used my lead with his laptop and his telescope and everything worked fine. So faulty lead we thought. Replacement lead obtained, still no joy. My lead works with both scopes and both laptops (Friends runs Vista, mine runs XP)

    I've since bought a third lead, different brand, different shop and this doesn't work on my laptop either. True I haven't tried the third lead on friends laptop. So thats three USB to serial converter leads which don't work with either telescope or laptop while my lead, which I had for some time, does work on both laptops and both scopes.

    The converter leads install in Device Mangler as "Prolific Serial to USB converter device (comx) where x varies.

    All my friend wants to do is connect his telescope to his laptop. We are running out of ideas - anyone help?????

    (p.s. if you are reading this and are thinking to yourself this doesn't make sense - me too!)
     
    Certifications: MCP, MCP+I, MCSE, MCSA, MCTS
    WIP: CCNA(?)
  2. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    It makes perfect sense - when you realize that many of the USB to RS232 converters do not implement most of the RS232 control signals.

    We have had this problem for ages here, where we need laptops to connect directly to serial-port console connections on routers and the like. Only a very few converters work - and these are jealously guarded by their owners! Others clash horribly with mobile-phone cables because the manufacturers failed to allocate unique numbers to the adaptors (I've had that on my old mobile).

    First of all - do the telescopes defines in their documentation how they use (if at all) CTS, DTS, DTR and RTS? Or are they simple 3-wire devices? If they need the control signals in a particular mode then sometimes you just need to rewire the cables to 'pretend' that lines are good. A RS232 break-out box comes in handy for this sort of work!

    Harry.
     
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  3. philbenson

    philbenson Byte Poster

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    Certifications: MCP, MCP+I, MCSE, MCSA, MCTS
    WIP: CCNA(?)
  4. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Hm - RJ11 to D9 is a very rare beast - Cisco uses similar things, but using RJ45 not RJ11. I suspect the wiring of the cable is the important thing here.

    I'd check *very* carefully that the correct pins are linked, and no other pins are linked. Look also for shorts.

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+
  5. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Oh - and while checking the D9 make *sure* you have identified pin 1 correctly. It is easy to get confused because the connector on the cable will be a female, not male one.

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+
  6. philbenson

    philbenson Byte Poster

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    Last night I tried the lead I got a couple of days ago on my laptop (XP) again. Nothing. So I completely un-installed it and then deleted the driver Windows installed in the Windows\system32\drivers folder.

    I then re-installed it with a driver supplied on the accompanying CD in a folder \Prolific\Vista_32bit. I assumed then that this was a certified Vista driver.

    Anyway once installed, the lead now works with my XP based laptop, but still not with my friends laptop which runs Vista! Every time I tried to install the driver, Vista threw up a message saying an error had been encountered while attempting to install device driver - invalid data in inf file.

    The Vista curse again it seems....

    Wouldn't be so bad but the BIOS in my friends HP laptop doesn't provide an option to disable AHCI and so I cannot install XP on it :-(
     
    Certifications: MCP, MCP+I, MCSE, MCSA, MCTS
    WIP: CCNA(?)

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