USB to Serial

Discussion in 'General Electronics Chat' started by ectmlk, Apr 25, 2008.

  1. ectmlk

    Thread Starter Member

    Feb 11, 2008
    21
    0
    Hey
    I have a USB to Serial converter, i wanted to use it to communicate with a modem via hyper terminal, i have used this converter before and it worked however i am having problems transmitting data.

    It worked perfect on another laptop (laptop B).
    If i connect the USB to Serial to Laptop A and connect Laptop A to Laptop B via RS232 Communications, then setup hyperterminal on both (same baud, e.tc) i can send typed messages from Laptop B to Labtop A however i can't send from Laptop A to Laptop B.

    From all this testing, I know the serial converter works on another PC, i know it gets setup on Laptop A ok because i can receive data but i can't figure out why i can't transmit anything from Laptop A.

    I have tried to disable firewalls, reinstall drivers. I have also used a free serial port monitor, this shows the messages i type in hyperterminal i.e hyperterminal is passing the data successfully, i just dont know where its getting lost.

    Any idea appreciated.


    Mike
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Do you have them both set to 8,N,1?
    8 bits, no parity, 1 stop bit?

    Does the hardware configuration match the software configuration?

    Did you try swapping ends of the RS-232 cable?

    Are you sure the pins are all OK on the end that's not transmitting? You might've blown the port, or snapped off one of the pins on the cable, or the wires internal to the cable.

    Use a meter to ring out the cable.
    See this page:
    http://www.lammertbies.nl/comm/cable/RS-232.html
    You should be using a null modem cable with handshaking. Loopback handshaking typically works pretty well.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    This sounds a lot like a null modem issue, if it worked with a modem. Null modems are necessary to get 2 computers to talk to each other on RS232 setups.

    They are easy to build, or you can buy them everywhere.
     
  4. ectmlk

    Thread Starter Member

    Feb 11, 2008
    21
    0
    Basically i can take the USB to Serial Converter and plug it into another
    laptop and it works perfect with the modem. It seems like the transmission is getting blocked by Windows XP or the USB drivers are wrong. (i have tried reinstalling the USB to Serial Converter drivers but there must be other software involved). I 've also plugged it into a diiferent usb port.

    Does anybody know where i can get a completely free USB monitor, i have HHD device monitoring but it has expired!! With this i can check the USb comms and compare between both laptops.

    Thanks for suggestions

    Mike
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    USB drivers seem to get corrupted easily. The easiest way to fix such problems is to go into the Control Panel/System/Device Mangler and just uninstall all of the items under USB and/or USB Controller, and let the OS reinstall the drivers on reboot.

    Uninstall your USB serial converter drivers before you uninstall the USB controller. Reinstall the drivers after you've rebooted, and your usb port is working normally.
     
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