Redirecting AT commands to microcom command under Linux

in the `BusyBox` command for Linux exists the command `microcom` to communicate with a serial modem: ``` BusyBox v1.13.2 (2012-05-10 17:13:08 CEST) multi-call binary Usage: microcom [-d DELAY] [-t TIMEOUT] [-s SPEED] [-X] TTY Copy bytes for stdin to TTY and from TTY to stdout Options: -d Wait up to DELAY ms for TTY output before sending every next byte to it -t Exit if both stdin and TTY are silent for TIMEOUT ms -s Set serial line to SPEED -X Disable special meaning of NUL and Ctrl-X from stdin ``` Instead of using stdin to type the AT commands I want to place them insise a text file and redirect the content of that file as the stdin for the above command. For example, I have a file ``` /tmp/at.txt ``` with the AT command `AT`, which usually gets confirmed by the TTY with an `OK`. A standard session with stdin looks like: ``` microcom -t 3000 -X /dev/ttyS5 at OK ``` in which the string `at` was entered directly on the keyboard. In order to use the content of the file `/tmp/at.txt` (contains just 'at\n'). To do this,. I have tried the following variations: ``` microcom -t 3000 -X /dev/ttyS5 < /tmp/at.txt microcom -t 3000 /dev/ttyS5 < /tmp/at.txt cat /tmp/at.txt | microcom -t 3000 /dev/ttyS5 tail -f /tmp/at.txt | microcom -t 3000 /dev/ttyS5 cat /tmp/at.txt | microcom -t 3000 /dev/ttyS5 -X tail -f /tmp/at.txt | microcom -t 3000 /dev/ttyS5 -X ``` and none of them worked, i.e. none of those commands did return the text 'OK' on the screen. I therefore conclude that there is some problem redirecting the content of the file `/tmp/at.txt` as stdin for the command `microcom`. Maybe is has to do with how the end-of-line is interpreted or the end-of-file. If someone has some idea, I would appreciate some help. Thanks, Alex