Question on system command 1.4.43

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I have a USB to serial converter attached to my box. pl2303: Prolific
PL2303 USB to serial adaptor driver
if I login to the box and send/receive serial commands over this unit it
works without error EVERY time.

however, if I run the same command set from with-in the extensions.conf
with System()
I get errors in dmesg like “pl2303 ttyUSB0: pl2303_open – failed
submitting read urb, error -22″
and then obviusly my command does not work.

however, again – If I go back to the command line and my command it runs
just fine.

Any ideas on what might be happening here?


exten => s,1,ChanIsAvail(Console/Dsp)
exten => s,n,GotoIf($[“${AVAILCHAN}” = “”]?smvoice-busy,s,1)
exten => s,n,System(/home/silentm/bin/usbserial -start)
exten => s,n,Playback(beep)
exten => s,n,Dial(Console/dsp)
exten => s,n,Hangup
exten => h,1,System(/home/silentm/bin/usbserial -stop)

5 thoughts on - Question on system command 1.4.43

  • Jerry Geis wrote:

    If Asterisk isn’t running as root, my guess would be a permissions issue.

    By the way, out of curiosity, what does “usbserial -start” do? I’m
    guessing, some type of paging busy notification?


  • Jim and Doug

    Yes the process is running as root. I should have mentioned that.
    Also – yes the usbserial is a paging notification program.

    So if its not permissions (since its running as root) what else might it be?



  • (Assuming /home/silentm/bin/ is not an NFS mount that root can’t access as

    PATH or other environment variables?


    sudo env –ignore /home/silentm/bin/usbserial -start

    yield any clues?