#picocom Minimal dumb-terminal emulator
by Nick Patavalis (npat@efault.net)
The latest release can be downloaded from:
As its name suggests, picocom is a minimal dumb-terminal emulation program. It is, in principle, very much like minicom, only it's "pico" instead of "mini"!
It was designed to serve as a simple, manual, modem configuration, testing, and debugging tool. It has also served (quite well) as a low-tech serial communications program to allow access to all types of devices that provide serial consoles. It could also prove useful in many other similar tasks.
It is ideal for embedded systems since its memory footprint is minimal (approximately 30K, when stripped). Apart from being a handy little tool, picocom's source distribution includes a simple, easy to use, and thoroughly documented terminal-management library, which could serve other projects as well. This library hides the termios(3) calls, and provides a less complex and safer (though certainly less feature-rich) interface. picocom runs on Linux, and with no or minor modifications it could run on any Unix-like system with the termios(3) library.
For a description of picocom's operation, its command line options, and usage examples, see the manual page included in the source distribution as "picocom.1", and also html-ized as "picocom.1.html".
People who have contibuted to picocom, by offering feature implementations, bug-fixes, corrections, and suggestions are listed in the "CONTRIBUTORS" file.
Please feel free to send comments, requests for new features (no promisses, though!), bug-fixes and rants, to the author's email address shown at the top of this file.
Compilation / Installation
Change into picocom's source directory and say:
make
This will be enough to compile picocom for most modern Unix-like systems. If you want, you can then strip the resulting binary like this:
strip picocom
Striping the binary is not required, it just reduces its size by a few kilobytes. Then you can copy the picocom binary, as well as the man-page, to wherever you put your binaries and man-pages. For example:
cp picocom ~/bin
cp picocom.1 ~/man/man1
Again, this is not strictly necessary. You can run picocom and read its man-page directly from the source directory.
If something goes wrong and picocom can't compile cleanly, or if it's lacking a feature you need, take a look at the included Makefile. It's very simple and easy to understand. It allows you to select compile-time options and enable or disable some compile-time features by commenting in or out the respective lines. Once you edit the Makefile, to recompile say:
make clean
make
If your system's default make(1) command is not GNU Make (or compatible enough), find out how you can run GNU Make on your system. For example:
gmake clean
gmake
Alternatively, you might have to make some trivial edits to the Makefile for it to work with your system's make(1) command.
Using picocom
If your computer is a PC and has the standard on-board RS-233 ports
(usually accessible as two male DB9 connectors at the back) then under
Linux these are accessed through device nodes most likely named:
/dev/ttyS0 and /dev/ttyS1. If your computer has no on-board serial
ports, then you will need a USB-to-Serial adapter (or something
similar). Once inserted to a USB port and recognized by Linux, a
device node is created for each serial port accessed through the
adapter(s). These nodes are most likely named /dev/ttyUSB0,
/dev/ttyUSB1, and so on. For other systems and other Unix-like OSes
you will have to consult their documentation as to how the serial port
device nodes are named. Lets assume your serial port is accessed
through a device node named /dev/ttyS0.
You can start picocom with its default option values (default serial port settings) like this:
picocom /dev/ttyS0
If you have not installed the picocom binary to a suitable place, then you can run it directly from the source distribution directory like this:
./picocom /dev/ttyS0
If this fails with a message like:
FATAL: cannot open /dev/ttyS0: Permission denied
This means that you do not have permissions to access the serial port's device node. To overcome this you can run picocom as root:
sudo picocom /dev/ttyS0
Alternatively, and preferably, you can add yourself to the user-group that your system has for allowing access to serial ports. For most Unix-like systems this group is called "dialout". Consult you system's documentation to find out how you can do this (as it differs form system to system). On most Linux systems you can do it like this:
sudo usermod -a -G dialout username
You will need to log-out and then log-in back again for this change to take effect.
You can explicitly set one or more of the serial port settings to the desired values using picocom's command line options. For example, to set the baud-rate to 115200bps (the default is 9600bps), and enable hardware flow-control (RTS/CTS handshake) you can say:
picocom -b 115200 -f h /dev/ttyS0
or:
picocom --baud 115200 --flow h /dev/ttyS0
To see all available options run picocom like this:
picocom --help
Once picocom starts, it initializes the serial port and prints the message:
Terminal is ready
From now on, every character you type is sent to the serial port, and every character received from the serial port is sent ro your terminal. Including control and special characters. Assuming that there is nothing connected to the other end of your serial port, to respond to the characters you send it (e.g. echo them back to you), then nothing that you type in picocom will appear on your terminal. This is normal.
To exit picocom you have to type:
C-a, C-x
Which means you have to type [Conttol-A] followed by [Control-X]. You can do this by pressing and holding down the [Control] key, then pressing (and releasing) the [A] key and then pressing (and releasing) the [X] key (while you still keep [Control] held down).
This C-a is called the "escape character". It is used to inform
picocom that the next character typed is to be interpreted as a
command to picocom itself (in this case the exit command) and not to
be sent-down to the serial port. There are several other commands
(other than C-a, C-x), all prefixed by C-a.
Next you should take a look at the very detailed picocom manual page. It can be accessed like this (assuming you are inside the picocom distribution source directory):
man ./picocom.1
or (assuming you have installed the manual page to a suitable place):
man picocom
Thanks for using picocom