writing to serial port from linux command line

Question

From windows I can communicate with a serial port device using following commands   mode com1  baud 9600 data 8 parity n stop 1 copy con com1 alt 18alt 2ctrl z   Device starts the requested operation   When I try to accomplish the same operation from a stand alone debian box or from a debian virtualbox instance of the same windows machine  I had no luck so far   Here s equivalent linux commands at least I think so   stty -F  dev ttyS0 speed 9600 cs8 -cstopb -parenb echo   x12 x02   gt   dev ttyS0   Nothing happens   Can somebody please direct me to the right direction

User · Answer

SCREEN   NOTE  screen is actually not able to send hex  as far as I know   To do that  use echo or printf  I was using the suggestions in this post to write to a serial port  then using the info from another post to read from the port  with mixed results   I found that using screen is an  easier  solution  since it opens a terminal session directly with that port   I put easier in quotes  because screen has a really weird interface  IMO  and takes some further reading to figure it out    You can issue this command to open a screen session  then anything you type will be sent to the port  plus the return values will be printed below it   screen  dev ttyS0 19200 cs8    Change the above to fit your needs for speed  parity  stop bits  etc    I realize screen isn t the  linux command line  as the post specifically asks for  but I think it s in the same spirit  Plus  you don t have to type echo and quotes every time   ECHO   Follow praetorian droid s answer   HOWEVER  this didn t work for me until I also used the cat command   cat  lt   dev ttyS0  while I was sending the echo command   PRINTF   I found that one can also use printf s   x  command   c   x   printf   x  0x12  printf  c  gt  gt   SERIAL COMM PORT   Again  for printf  start cat  lt   dev ttyS0 before sending the command

User · Answer

echo   x12 x02    will not be interpreted  and will literally write the string  x12 x02  and append a newline  to the specified serial port   Instead use  echo -n  R B   which you can construct on the command line by typing CtrlVCtrlR and CtrlVCtrlB   Or it is easier to use an editor to type into a script file   The stty command should work  unless another program is interfering   A common culprit is gpsd which looks for GPS devices being plugged in

User · Answer

If you want to use hex codes  you should add -e option to enable interpretation of backslash escapes by echo  but the result is the same as with echoCtrlRCtrlB   And as wallyk said  you probably want to add -n to prevent the output of a newline   echo -en   x12 x02   gt   dev ttyS0   Also make sure that  dev ttyS0 is the port you want

[linux] writing to serial port from linux command line

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