Direct access to RS-232 in Windows XP

Discussion in 'Embedded Systems and Microcontrollers' started by veridian, Feb 27, 2009.

  1. veridian

    Thread Starter New Member

    Feb 27, 2009
    What additional drivers/software I need to get direct access to serial port RS-232 in Windows XP (the same like it was possible in Win98)

    I have laptop with RS-232, but I can not establish communication with GSM modem via RS-232. My OS is WIN XP and I already found that it is the issue (with WIN 98 modem works perfect!)

    Please give me any suggestions
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Try your device manager. Mine shows COM1 just fine (XP Pro). Checking with the topic in help suggests it's there for things like a GSM modem - mentions it specifically.

    Are you sure that is a serial port?
  3. veridian

    Thread Starter New Member

    Feb 27, 2009
    I'm sure it is a serial port RS-232. GSM modem - Wavecom Fastrack 1206. I can see COM1 in my device manager (XP Pro), but I can not communicate with modem, even using AT commands from Hyper Terminal. When I connect to the computer with Win98 than I can "talk" with modem using AT commands. Thus I'm sure that problem is in software.
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
    I expect it's a question of voltage levels.

    The original serial (later RS232) usually used ±12 volts for signalling. ( There was an even older standard but I won't discuss that)

    When personal computers first came out, many cut this down to ±9.

    Later pcs cut this down again to ±5.

    Some pcs now even dispense with the -5 line.

    So I suspect that your newer laptop is simply not producing enough oomph to drive the modem, especially if older equipment does so satisfactorily
  5. russ_hensel

    Distinguished Member

    Jan 11, 2009
    There may be drivers out there, but it is not clear that lack of direct access to the port is your problem. Could be you port is blown or any number of other things. Most modern operating systems for PC class computers virtualize all the ports and you can access only the os facilities. This lets you use usb as if it were RS232.

    What make you think that you need to set the hardware yourself ( for example setting to 357 baud )?