Shop OBEX P1 Docs P2 Docs Learn Events
Virtual Serial Ports — Parallax Forums

Virtual Serial Ports

Tony RichardsonTony Richardson Posts: 3
edited 2008-08-19 13:33 in Robotics
I am trying to use the com0com and hub4com software to
create a virtual null modem cable to program the scribbler over
a Bluetooth/serial link.· (A physical null modem cable between
the BT/RS232 device and the Scribbler works, but a virtual
null modem cable is easier to wire-up.· The BT/RS232 device
I have does not have a DTE/DCE switch so I need the cable.)

The Scribbler programming software (both the GUI and
the Editor) refuses to recognize the virtual serial port
as a valid com port.· I've tried passing the com port
as an argument to the stampw program, but still no success.
The software does recognize my virtual bluetooth com
port, but not my com0com port.· I'm guessing no one
has tried this setup before, but can someone provide
some hints/guesses as to what might be wrong?

Tony Richardson

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-08-12 23:46
    Tony,

    A null-modem cable should not work or be used in the connection. A standard straight-through serial cable should be used. As for issues with virtual connections, these usually fail due to timing issues with the signals. In a wireless system any corruption of the signal which causes a NAK or resend of the data will fail communication with the BASIC Stamp. Systems that were available in the past used a buffering system to store the code on the target end before actually programming the BASIC Stamp.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
  • Tony RichardsonTony Richardson Posts: 3
    edited 2008-08-13 02:16
    Chris,

    Thanks for replying.· I need the null modem because the BT connection I currently have

    emulates a null modem cable.· I need a second one to "undo" the·emulated one.

    A physical null modem cable between the BT/serial converter and the scribbler works.

    (The BT/serial converter and cable ride on the scribbler.)· This setup works.

    I was hoping to use a virtual null modem cable on the PC to replace the physical

    cable that rides on the scribbler.· This would allow me to plug the BT/serial converter

    directly into the scribbler.· Unfortunately, the scribbler software does not detect the

    virtual serial port that is created by the virtual null modem.

    Tony
  • Peter VerkaikPeter Verkaik Posts: 3,956
    edited 2008-08-13 05:05
    You probably need to rename the virtual ports from CNCx to COMx
    because I don't think the software recognizes CNCx as a valid port name.

    regards peter
  • Tony RichardsonTony Richardson Posts: 3
    edited 2008-08-13 13:22
    Yes, I've done that. I found the answer on the com0com forum.
    I'll include it below for the form archives.

    Tony Richardson

    You can "deceive" the robot software this way:

    1. With the "Add/Remove Hardware" wizard install new
    standard serial port. You don't need a real serial
    hardware to do it. Select non conflicted IO/IRQ
    resources.
    2. With the "Device Manager" disable the newly created
    port (let it be COM4).
    3. With the "Setup Command Prompt" for com0com install the
    pair of ports, were one of them has name COM4. Ignore
    warning about the COM4 is "in use" (press Continue).
  • Justin RatliffJustin Ratliff Posts: 14
    edited 2008-08-19 13:33
    Tony, did this let you "program" the scribbler or just send commands to it?

    -Justin Ratliff
    The Robotics Club of Yahoo
    www.trcy.org
Sign In or Register to comment.