A Minicom like shell in Python

serial, minicom
pip install pynicom==0.3.5


Pynicom: A Minicom like shell in Python

Pynicom reproduces the behavior of Minicom, adding some utilities:

  • command history
  • autocompletion
  • inline help
  • pattern highlight (optional)

Auto-completion and inline help are available using a _dictionary_ file. Each entry in the file has the format

command-name # <inline-help>


AT+FCLASS # Select Active Service Class AT+GCAP # Capabilities list AT+GMI # Manufacturer identification

Of course all the commands written in the command-line are sent to the serial device even if they are not in the dictionary file.

_dictionary_ file is saved as hidden file in your HOME folder and named _.pynicom-dictionary_and it is empty when Pynicom is first installed. Feel free to copy the example on Pycom's project page on [GitHub]( in your own dictionary file.


  1. Install PyPI module manager

    sudo apt-get install python-pip

  2. Install dependencies: docopt, pyserial, readline (optional [raffaello]( for pattern highlight)

    sudo pip <module-name>


On GNU/Linux, Pynicom need administrative privilegies to access the serial device. On Debian/Ubuntu and derivates this can be done running the following command:

$ sudo pynicom

First steps

Auto-completion is obtained with with a double tab

A Minicom like shell in Python3 author: Carlo Lobrano version: 0.1.0

pynicom [-d|--debug] [--port=port --baud=rate --bytesize=bytesize --parity=parity --stopbits=stopbits --sw-flow-ctrl=xonxoff --hw-rts-cts=rtscts --hw-dsr-dtr=dsrdtr --timeout=timeout]

(no-conn)<Tab><Tab> AT at exit quit serial_info serial_read set_bytesize set_parity set_stopbits shell ATE ate help serial_close serial_open set_baudrate set_debug set_port set_timeout show_dictionary (no-conn)

a known limitation is that the extended commands (+,&,#,...) are auto-completed after typing at least the symbol

(/dev/ttyACM0 @ 115200) at<Tab><Tab> at ate (/dev/ttyACM0 @ 115200) at+<Tab><Tab> CGDCONT CGI CGREG CREG FCLASS GCAP GMI GMM GMR GSN (/dev/ttyACM0 @ 115200) at+

As you could see, the prompt shows the current serial device used and the baud rate or "no-conn".

To use the inline help, issue the command: 'help command-name' or '?command-name'

(no-conn) help serial_open

Open the given serial device.

Example: serial_open /dev/ttyUSB0 115200 8 N 1 False False False 1

where the args are respectively: port, baudrate, bytesize, parity, stopbits, SW flow control, HW flow control RTS/CTS, HW flow control DSR/DTR, timeout. You do not need to give all the parameters, if you are fine with the default values, just give the serial device path.

The connection to the serial device can be established also with Pynicom arguments:

$ sudo pynicom --port=/dev/ttyACM0 --baud=115200

A Minicom like shell in Python author: Carlo Lobrano version: 0.1.0

pynicom [-d|--debug] [--port=port --baud=rate --bytesize=bytesize --parity=parity --stopbits=stopbits --sw-flow-ctrl=xonxoff --hw-rts-cts=rtscts --hw-dsr-dtr=dsrdtr --timeout=timeout]

(/dev/ttyACM0 @ 115200)

To see all input arguments type

$ pynicom -h

Connection parameters can be changed using the set_ commands without closing and opening again the connection:

(/dev/ttyACM0 @ 115200) set_ set_baudrate set_bytesize set_debug set_parity set_port set_stopbits set_timeout

serial_info shows the current connection's info

(/dev/ttyACM0 @ 115200) serial_info
Serial<id=0x7fbf8df8af50, open=True>(port='/dev/ttyACM0', baudrate=115200, bytesize=8, parity='N', stopbits=1, timeout=1, xonxoff=False, rtscts=False, dsrdtr=False)

the special character '!' execute system's commands:

(/dev/ttyACM0 @ 115200) !ls -la total 25 drwxrwx--- 1 root vboxsf 0 lug 2 10:25 . drwxrwx--- 1 root vboxsf 4096 lug 2 10:25 .. -rwxrwx--- 1 root vboxsf 1439 lug 2 08:57 dictionary.txt -rwxrwx--- 1 root vboxsf 1 lug 2 08:57 errors.txt -rwxrwx--- 1 root vboxsf 0 lug 2 08:57 -rwxrwx--- 1 root vboxsf 15417 lug 2 10:24 -rwxrwx--- 1 root vboxsf 390 lug 2 08:57 -rwxrwx--- 1 root vboxsf 2115 lug 2 08:57

All commands have 1 seconds timeout as default, but that can be changed with set_timeout command. If a command does not return, stop it with CTRL-B or CTRL-C

Highlight patterns

The [Raffaello]( module allows Pynicom to highlight the text ouput. You can choose a pattern to be highlighted in a given color (the available colors depending on the Shell)

(/dev/ttyUSB0 @ 9600) highlight GNRMC=>green

this can be useful when reading NMEA sentences for example (with serial_read)

use show_highlight to see the current highlighted patterns and remove_highlight to remove a pattern.

(/dev/ttyUSB0 @ 9600) show_highlight
{'GNRMC': green}

(/dev/ttyUSB0 @ 9600) remove_highlight GNRMC (/dev/ttyUSB0 @ 9600) show_highlight


NMEA sentences

Nmea sentences can be sent to the serial device using the nmea command. Pycom will automatically add the initial '$' symbol, the checksum and the final appendix (<CR><LF>), so that a possible usage of this API is the following:

(/dev/ttyUSB0 @ 9600) nmea PMTK430
nmea > "$PMTK430*35<CR><LF>"
$GLGSV,2,1,06,84,81,030,43,74,78,042,46,85,44,215,48,73,35,128,36*62 $GLGSV,2,2,06,75,31,326,44,83,25,033,44*68 $GNRMC,115725.000,A,3913.6604,N,00904.1282,E,0.00,51.50,060715,,,D*4C $GNVTG,51.50,T,,M,0.00,N,0.01,K,D*16 $PMTK530,0*28

after sending the nmea message, pynicom will automaticalli issue serial_read command. You will stop reading using CTRL-C.