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Thread: trying to change baud rate with stty

  1. #1
    Join Date
    Sep 2008
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    Ubuntu 12.04 Precise Pangolin

    trying to change baud rate with stty

    I am using the command:

    Code:
    sudo stty -F /dev/ttyUSB0 115200
    to try and change the baud rate from 9600 to 115200 on device USB0, but I keep getting this error.

    Code:
    stty: /dev/ttyUSB0: unable to perform all requested operations
    ttyUSB0 is not locked, and I know it is capable of 230400 b/s so I know it should handle 115200 just fine. Any ideas?

  2. #2
    Join Date
    Oct 2009
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    Re: trying to change baud rate with stty

    I believe stty is for setting the baud rate of a terminal.

    The setserial command is used to set the baud rate of a serial port(unless Ubuntu uses something else, because setserial is not installed by default)

  3. #3
    Join Date
    Oct 2010
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    Question Re: trying to change baud rate with stty

    A related question: Is it possible to change the baud rate to 2,000,000 in Ubuntu? It works fine with Windows XP. Thanks!

    Here is the current setserial info:
    Code:
    setserial -a /dev/ttyUSB0 
    /dev/ttyUSB0, Line 0, UART: unknown, Port: 0x0000, IRQ: 0
        Baud_base: 24000000, close_delay: 0, divisor: 0
        closing_wait: infinite
        Flags: spd_normal low_latency
    Does this mean if I set divisor to 12 then I get 2000000? Thanks!
    Last edited by adummy; November 1st, 2010 at 12:16 AM.

  4. #4
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    Ubuntu 12.04 Precise Pangolin

    Re: trying to change baud rate with stty

    Quote Originally Posted by efflandt View Post
    I believe stty is for setting the baud rate of a terminal.

    The setserial command is used to set the baud rate of a serial port(unless Ubuntu uses something else, because setserial is not installed by default)
    Sorry should of mention this before I get the same error message with setserial

    Code:
    sudo setserial /dev/ttyUSB0
    Cannot get serial info: Invalid argument
    I know it works because i can use screen to talk to it just fine.

    Code:
    screen /dev/ttyUSB0 230400
    Any ideas?

  5. #5
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    Ubuntu 12.04 Precise Pangolin

    Re: trying to change baud rate with stty

    Is there any way to configure ttyUSB* before the USB serial device is plugged in or to configure it permanently?

  6. #6
    Join Date
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    Re: trying to change baud rate with stty

    What kind of USB to serial device do you have? It works for me for just the USB/serial cable with nothing connected to it:

    lsusb | grep -i serial
    Bus 002 Device 004: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

    sudo setserial -av /dev/ttyUSB0
    Code:
    /dev/ttyUSB0, Line 0, UART: 16654, Port: 0x0000, IRQ: 0
        Baud_base: 460800, close_delay: 0, divisor: 0
        closing_wait: infinite
        Flags: spd_normal
    PS: I cannot change any settings though. Maybe that is simply determined by whatever pace programs or devices communicate through it.

    I wonder if my USB cable is USB 1.0 and adummy's is USB 2.0. The one I got is just to communicate with an ancient Garmin GPS45 (from mid-1990's) at 4800 baud. Although, I have not figured out how to do that in Linux yet (programs seem to use minimum 9600 baud).
    Last edited by efflandt; November 2nd, 2010 at 03:45 AM.

  7. #7
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    Re: trying to change baud rate with stty

    I don't have the hookup right now because I left it at work, but I'll post up what lsusb prints out. The hardware is a 3G cellular modem hooked with a 2.0 USB cord and the computer sees 4 serial hookups 2 of which I can talk to and use for a connection. First step change the baud rate. Second step set it up so both connections are seen as one. Got a lot of debugging to do .

    My problem is setserial can't talk to it at all. can't even get a print out from setserial.

  8. #8
    Join Date
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    Al Ain
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    Re: trying to change baud rate with stty

    Howdy,

    Use Cutecom (very nice) or Minicom (clunky).

  9. #9
    Join Date
    Sep 2008
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    Re: trying to change baud rate with stty

    I actually prefer screen, but I use wvdial and pppd to connect. My problem is I can't change the baud rate to get the full potential out of my modem though.

  10. #10
    Join Date
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    Re: trying to change baud rate with stty

    Well I guess this solves my problem my computer doesn't see the 4 ttyUSB* connections as serial ports.

    lsusb gives:

    Code:
    Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 007 Device 002: ID 1bc7:1004  
    Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 004 Device 002: ID 0461:4d64 Primax Electronics, Ltd 
    Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 002 Device 002: ID 058f:6363 Alcor Micro Corp. 
    Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 001 Device 003: ID 050d:845a Belkin Components 
    Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Code:
    lsusb | grep -i serial
    doesn't return anything

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