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Bash and serial port

Hello there !

I try to use bash for send datas to an external computer.

I have try this :

Code:

#!/bin/bash



file=$1

port="/dev/ttyUSB0"



while IFS= read -r line

do

        echo -n "$line" > $port

        sleep 0.5

done < "$file"

This work well but is to slow.

As soon the external computer has get the datas and made his job he send a single ">" (no crlf, no eol, etc...) to the serial port.
I think I can read the serial port and as soon as I get a ">" send the next line.

So I try

Code:

#!/bin/bash



file=$1

port="/dev/ttyUSB0"



while IFS= read -r line

do

        echo -n "$line" > $port

        while read -N1 char; do

                echo $char # just for debug purpose

        done < $port

done < "$file"

First problem I see is that the "read" instruction read again the data which just has been send by the previous line. So if by hazard the send data include a ">" the program will fail... Also this seems to remove datas from the serial port buffer.

And the "while read... done < $port" look to be an endless loop.

How could I change the code to do the job ?

Thanks for the help.
Philippe

IMHO bash is not the best language for accessing serial port data and can be unreliable. Here is a quick python script. Change serial port parameters as necessary. It will wait for a single character response and then continue sending data. The serial module is not installed by default.

Code:

#!/usr/bin/python3



import serial

import sys



if len(sys.argv) == 1:

    print("Missing command line argument")

    quit()



myfile=sys.argv[1]



serialport=serial.Serial(port="/dev/ttyUSB0",baudrate=9600,bytesize=8,timeout=2,stopbits=serial.STOPBITS_ONE)



file1 = open(myfile, 'r')

while True:

    # Get next line from file

    line = file1.readline()

    serialport.write(line.encode())

    # if line is empty

    # end of file is reached

    if not line:

        break

    while (serialport.in_waiting == 0):

          pass

file1.close()

@OP I guess you should open the device only once, e.g.

Code:

#!/bin/bash



file="$1"

port="/dev/ttyUSB0"

exec 7<>"$port"

# stty <&7 some-serial-options



while IFS= read -r line

do

    echo -n "$line" >&7

    while read -u7 -N1 char; do

        echo $char # just for debug purpose

    done

done <"$file"

I heartily agree with @michaelk: "use a real language." Also, avail yourself fully of the many packages that are available for use in those languages.

Quote:

Originally Posted by wisdom:

Actum Ne Agas: Do Not Do A Thing Already Done.

If you mark the script file as "executable" and it begins with a so-called "shebang" #! in the first line, specifying the location of a language interpreter, then that interpreter will silently be invoked to run the script and the user will be none the wiser. (The env command exists to make this easier.)

While "bash" has very rudimentary scripting capability, it never was intended to be used for "real work." (Only the Korn shell, "ksh," had a serious built-in language.) The elegantly-simple "shebang" mechanism means that it doesn't need to.