Provided by: picocom_3.1-4_amd64 
NAME
picocom - minimal dumb-terminal emulation program
SYNOPSIS
picocom [ options ] device
DESCRIPTION
As its name suggests, picocom(1) is a minimal dumb-terminal emulation program. It is, in principle, very
much like minicom(1), 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.
In effect, picocom is not an “emulator” per-se. It is a simple program that opens, configures, manages a
serial port (tty device) and its settings, and connects to it the terminal emulator you are, most likely,
already using (the terminal window application, xterm, rxvt, system console, etc).
When picocom starts it opens the tty (serial port) given as its non-option argument. Unless the –noinit
option is given, it configures the port to the settings specified by the option-arguments (or to some
default settings), and sets it to “raw” mode. If –noinit is given, the initialization and configuration
is skipped; the port is just opened. Following this, if standard input is a tty, picocom sets the tty to
raw mode. Then it goes in a loop where it listens for input from stdin, or from the serial port. Input
from the serial port is copied to the standard output while input from the standard input is copied to
the serial port. Picocom also scans its input stream for a user-specified control character, called the
escape character (being by default C-a). If the escape character is seen, then instead of sending it to
the serial-device, the program enters “command mode” and waits for the next character (which is called
the “function character”). Depending on the value of the function character, picocom performs one of the
operations described in the COMMANDS section below.
COMMANDS
Commands are given to picocom by first keying the espace character which by default is C-a (see OPTIONS
below for how to change it), and then keying one of the function (command) characters shown here.
escape character
Send the escape character to the serial port and return to “transparent” mode. This means that if
the escape character (C-a, by default) is typed twice, the program sends the escape character to
the serial port, and remains in transparent mode.
C-x Exit the program. If the –noreset option is not given, then the serial port is reset to its
original settings before exiting, and the modem control lines (typically DTR and RTS) are cleared
(lowered) signaling a modem hangup. If –noreset is given (and –hangup is not), then the serial
port settings are not reset, and the modem control lines remain unaffected. If both –noreset and
–hangup are given, then the serial port settings are not reset, but the modem-control lines are
cleared.
C-q Quit the program without resetting the serial port to its original settings. Terminating with the
Quit command, picocom behaves exactly as if the –noreset option was given. The serial port is not
reset to its original settings, and the modem control lines remain unaffected or are cleared,
subject to the –hangup option.
C-p Pulse the DTR line. Lower it for 1 sec, and then raise it again.
C-t Toggle the DTR line. If DTR is up, then lower it. If it is down, then raise it. May not be
supported on some systems.
C-g Toggle the RTS line. If RTS is up, then lower it. If it is down, then raise it. Not supported
if the flow control mode is RTS/CTS. May not be supported on some systems.
C-backslash
Generate a break sequence on the serial line. A break sequence is usually generated by marking
(driving to logical one) the serial Tx line for an amount of time coresponding to several
character durations.
C-b Set baudrate. Prompts you to enter a baudrate numerically (in bps) and configures the serial port
accordingly.
C-u Baud up. Increase the baud-rate. The list of baud-rates stepped-through by this command is: 50,
75, 110, 134, 150, 200, 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200. If
HIGH_BAUD support is compiled-in, then the following baud-rates are also added to the list:
230400, 460800, 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000, 2500000, 3000000,
3500000, 4000000. Depending on you system, any of the higher baud rates may be missing.
C-d Baud down. Decrease the baud-rate. The list of baud-rates stepped-through by this command is the
same as for the “baud-up” command.
C-f Cycle through flow-control settings (RTS/CTS, XON/XOFF, none).
C-y Cycle through parity settings (even, odd, none).
C-i Cycle through databits-number settings (5, 6, 7, 8).
C-j Cycle through stopbits-number settings (1, 2).
C-c Toggle local-echo mode.
C-w Write hex. Picococm prompts the user for a string of hexadecimal values. Values can be entered
with or without delimeters (separators). The hexadecimal values are translated to binary and sent
to the port, exactly as if input at the terminal (i.e. the –omap, –echo and –emap options are
observed). Example: The following sends the characters “ABCD” to the port.
C-a C-w
*** hex: 41 4243:44
*** wrote 4 bytes ***
C-s Send (upload) a file. See SENDING AND RECEIVING FILES below.
C-r Receive (download) a file. See SENDING AND RECEIVING FILES below.
C-v Show program options (like baud rate, data bits, etc) as well as the actual serial port settings.
Only the options and port settings that can be modified online (through commands) are shown, not
those that can only be set at the command-line. See DISPLAY OF OPTIONS AND PORT SETTINGS for
details.
C-h or C-k
Show help, or show keys. Prints a short description of all available function (command) keys.
After performing one of the above operations, the program leaves the command mode and enters transparent
mode. Example: To increase the baud-rate by two steps, you have to type:
C-a, C-u, C-a, C-u
assuming of-course that C-a is the escape character.
OPTIONS
Picocom accepts the following command-line options.
–baud | -b
Defines the baud-rate to set the serial-port (terminal) to.
–flow | -f
Defines the flow-control mode to set the serial-port to. Must be one of: x for xon/xoff
(software) mode, h for hardware flow control (RTS/CTS), n for no flow control. (Default: n)
–parity | -y
Defines the parity mode to set the serial-port to. Must be one of: o for odd parity mode, e for
even parity mode, n for no parity mode. (Default: n)
–databits | -d
Defines the number of data bits in every character. Must be one of: 5, 6, 7, 8. (Default: 8)
–stopbits | -p
Defines the number of stop bits in every character. Must be one of: 1, or 2. (Default: 1)
–escape | -e
Defines the character that will make picocom enter command-mode (see description above). If x is
given, then C-x will make picocom enter command mode. See also the –no-escape option. (Default:
a)
–no-escape | -n
Disables the escape character. Picocom will never enter command-mode if this option is given. To
exit picocom, in this case, you must either close its standard input, or send it the TERM or INT
signal. (Default: Disabled).
–echo | -c
Enable local echo. Every character being read from the terminal (standard input) is echoed to the
terminal (standard output) subject to the echo-mapping configuration (see –emap option).
(Default: Disabled)
–noinit | -i
If given, picocom will not initialize, configure, or otherwise mess with the serial port at start-
up. It will just open it. This is useful, for example, for connecting picocom to already-
connected modems, or already configured ports without terminating the connection, or altering
their settings. If required, serial port parameters can then be adjusted at run-time by commands.
See also the –noreset and –hangup options. (Default: Disabled)
–noreset | -r
If given, picocom will not reset the serial port when exiting. It will just close the respective
file descriptor and do nothing more. The serial port settings will not be restored to their
original values and, unless the –hangup option is also given, the modem-control lines will not be
affected. This is useful, for example, for leaving modems connected when exiting picocom.
Regardless whether the –noreset option is given, the user can exit picocom using the “Quit”
command (instead of “Exit”), which makes picocom behave exactly as if –noreset was given. See
also the –hangup option. (Default: Disabled)
NOTICE: Picocom clears the modem control lines on exit by setting the HUPCL control bit of the
respective port. Picocom always sets HUPCL according to the –noreset and –hangup options. If
–noreset is given and –hangup is not, then HUPCL for the port is cleared and will remain so after
exiting picocom. If –noreset is not given, or if both –noreset and –hangup are given, then HUPCL
is set for the port and will remain so after exiting picocom. This is true, regardless of the way
picocom terminates (command, read zero-bytes from standard input, killed by signal, fatal error,
etc), and regardless of the –noinit option.
–hangup | -u
If given together with –noreset, picocom will not reset the serial port to it’s original settings
on exit, but it will clear the modem control lines (typically DTR and RTS) to signal a modem
hangup. Without the –noreset option (explicitly given, or implied by extiting with the “Quit”
command) –hangup has no effect (without –noreset picocom always clears the modem control lines on
exit, anyway).
–nolock | -l
If given, picocom will not attempt to lock the serial port before opening it. Normally, depending
on how it’s compiled, picocom attempts to get a UUCP-style lock-file (e.g. `/var/lock/LCK..ttyS0')
before opening the port, or attempts to lock the port device-node using flock(2). Failing to do
so, results in the program exiting after emitting an error-message. It is possible that your
picocom binary is compiled without support for locking. In this case the –nolock option is
accepted, but has no effect. (Default: Disabled)
–send-cmd | -s
Specifies the external program (and any arguments to it) that will be used for transmitting files.
If the argument to –send-cmd is the empty string (’’), the send-file command is disabled. See
SENDING AND RECEIVING FILES. (Default: sz -vv)
–receive-cmd | -v
Specifies the external program (and any arguments to it) that will be used for receiving files.
If the argument to –receive-cmd is the empty string (’’), the receive-file command is disabled.
See SENDING AND RECEIVING FILES. (Default: rz -vv)
–imap Specifies the input character map (i.e. special characters to be replaced when read from the
serial port). See INPUT, OUTPUT, AND ECHO MAPPING. (Defaul: Empty)
–omap Specifies the output character map (i.e. special characters to be replaced before being written to
serial port). See INPUT, OUTPUT, AND ECHO MAPPING. (Defaul: Empty)
–emap Specifies the local-echo character map (i.e. special characters to be replaced before being
echoed-back to the terminal, if local-echo is enabled). See INPUT, OUTPUT, AND ECHO MAPPING.
(Defaul: delbs,crcrlf)
–logfile | -g
Use specified file for logging (recording) serial input, and possibly serial output. If the file
exists, it is appended to. Every character read from the serial port is written to the specified
file (before input mapping is performed). If local-echo mode is is enabled (see –echo option and
C-c command), then every character written to the serial port (after output mapping is performed)
is also logged to the same file. (Default: no logging)
–initstring | -t
Send the provided string after opening and configuring the serial port. The init string is sent
exactly as if it was input at the terminal. Sending the init string, picocom observes the –omap
output mapping, the –echo local-echo setting, and the –emap local-echo mapping. This feature is
useful, for example, if the serial device needs some special magic strings to start responding.
Use echo(1) or xxd(1) to generate special characters like a CR or binary data. Example:
picocom -t "$(echo -ne 'AAATZ\r\n')" /dev/ttyS0
Note, that the init string is not sent if –noinit is given. (Default: empty).
–lower-rts
Lower the RTS modem control signal after opening the serial port. Only supported when flow-
control mode is not set to RTS/CTS, ignored otherwise. Only supported on some systems.
If neither –lower-rts nor –raise-rts are given, the state of the RTS signal, after opening and
configuring the port, is system dependent. On most systems the signal is raised.
–raise-rts
Raise the RTS modem control signal after opening the serial port. Only supported when flow-
control mode is not set to RTS/CTS, ignored otherwise. Only supported on some systems.
If neither –raise-rts nor –lower-rts are given, the state of the RTS signal, after opening and
configuring the port, is system dependent. On most systems the signal is raised.
–lower-dtr
Lower the DTR control signal after opening the serial port. Only supported on some systems.
If neither –lower-dtr nor –raise-dtr are given, the state of the DTR signal, after opening and
configuring the port, is system dependent. On most systems the signal is raised.
–raise-dtr
Raise the DTR control signal after opening the serial port. Only supported on some systems.
If neither –raise-dtr nor –lower-dtr are given, the state of the DTR signal, after opening and
configuring the port, is system dependent. On most systems the signal is raised.
–exit-aftrer | -x
Exit picocom if it remains idle for the specified time (in milliseconds). Picocom is considered
idle if: Nothing is read (received) from the serial port, AND there is nothing to write (send) to
the serial port, AND nothing is read from the standard input (terminal). If –exit-after is set to
zero, then picocom exits after opening and configuring the serial port, after sending the init
string (if any, see option –initstring) and imediatelly when it becomes idle. When exiting after
being idle, picocom drains the O/S serial port ouput buffer (i.e. waits for data already written
to the port to be transmitted) and observes the –noreset and –hangup options as usual. (Default:
not set).
NOTICE: If –exit-after is set, reading zero bytes from the standard input (which usually means
that whatever was connected there has been closed), will not cause picocom to exit. Instead,
picocom will keep running, without reading from stdin, and will exit only when it becomes idle for
the specified time, or if it is killed by a signal. If –exit-after is not set, then reading zero
bytes from the standard input causes picocom to exit, after the contents of its output queue have
been transmitted.
–exit | -X
Exit picocom immediatelly after opening and configuring the serial port. Do not read anything
from the standard input or from the serial port. When exiting the –noreset and –hangup options
are observed as usual. With –exit and –noreset (and possibly –hangup) picocom can be used as a
very crude replacement of stty(1). If an init string is also given (see –initstring option),
picocom exits imediatelly after sending (writing) the init string to the serial port and draining
the O/S serial port output buffer (i.e. waiting for data written to the port to be transmitted).
Again, nothing is read from the standard input, or from the serial port. The –exit option,
overrides the –exit-after option. (Default: Disabled)
–quiet | -q
Forces picocom to be quiet. Suppresses the output of the initial status and options information,
as well as any other information or messages not explicitly requested by the user. Responses to
user commands and any error or warning messages are still printed.
–help | -h
Print a short help message describing the command-line options. Picocom’s version, compile-time
options, and enabled features are also shown.
DISPLAY OF OPTIONS AND PORT SETTINGS
The “show program options” command (C-v), as well as the commands that change program options (C-b, C-u,
C-d, C-f, etc) print messages showing the current values (or the new values, if they were changed) for
the respective options. If picocom determines that an actual serial-port setting differs from the
current value of the respective option (for whatever reason), then the value of the option is shown
followed by the value of the actual serial-port setting in parenthesis. Example:
*** baud: 115200 (9600)
This means that a baud rate of 115200bps has been selected (from the command line, or using commands that
change the baudrate) but the serial-port is actually operating at 9600bps (the driver may not support the
higher setting, and has silently replaced it with a safe default, or the setting may have been changed
from outside picocom). If the option and the corresponding serial-port setting are the same, only a
single value is shown. Example:
*** baud: 9600
This behavior was introduced in picocom 2.0. Older releases displayed only the option values, not the
actual serial-port settings corresponding to them.
On startup, after the serial port is opened and configured (and assuming that neither the –noinit, nor
the –quiet command line options have been given), the port settings are silently checked. If any
mismatch is detected between the requested and the actual port settings, a warning message is displayed.
You may then use the C-v command to determine the exact mismatch or mismatches.
SENDING AND RECEIVING FILES
Picocom can send and receive files over the serial port using external programs that implement the
respective protocols. In Linux typical programs for this purpose are:
• rx(1) - receive using the X-MODEM protocol
• rb(1) - receive using the Y-MODEM protocol
• rz(1) - receive using the Z-MODEM protocol
• sx(1) - send using the X-MODEM protocol
• sb(1) - send using the Y-MODEM protocol
• sz(1) - send using the Z-MODEM protocol
• ascii-xfr(1) - receive or transmit ASCII files
The name of, and the command-line options to, the program to be used for transmitting files are given by
the –send-cmd option. Similarly the program to receive files, and its arguments, are given by the
–receive-cmd option. For example, in order to start a picocom session that uses sz(1) to transmit files,
and rz(1) to receive files, you have to say something like this:
picocom --send-cmd "sz -vv" --receive-cmd "rz -vv" ...
If the argument to the -send-cmd option, or the argument to the –receive-cmd option is the empty string,
then the respective command is disabled. For example, in order to disable both the “send” and the
“receive” commands you can invoke picocom like this:
picocom --send-cmd '' --receive-cmd '' ...
A picocom session with both, the send- and the receive-file commands disabled does not fork(2) and does
not run any external programs.
During the picocom session, if you key the “send” or “receive” commands (e.g. by pressing C-a, C-s, or C-
a, C-r) you will be prompted for a filename. At this prompt you can enter one or more file-names, and
any additional arguments to the transmission or reception program. Command-line editing and rudimentary
pathname completion are available at this prompt, if you have compiled picocom with support for the
linenoise library. Pressing C-c at this prompt will cancel the file transfer command and return to
normal picocom operation. After entering a filename (and / or additional transmission or reception
program arguments) and assuming you have not canceled the operation by pressing C-c, picocom will start
the external program as specified by the –send-cmd, or –receive-cmd option, and with any filenames and
additional arguments you may have supplied. The standard input and output of the external program will
be connected to the serial port. The standard error of the external program will be connected to the
terminal which—while the program is running—will revert to canonical mode. Pressing C-c while the
external program is running will prematurely terminate it (assuming that the program itself does not
ignore SIGINT), and return control to picocom. Pressing C-c at any other time, has no special effect;
the character is normally passed to the serial port.
INPUT, OUTPUT, AND ECHO MAPPING
Using the –imap, –omap, and –emap options you can make picocom map (translate, replace) certain special
characters after being read from the serial port (with –imap), before being written to the serial port
(with –omap), and before being locally echoed to the terminal (standard output) if local echo is enabled
(with –emap). These mapping options take, each, a single argument which is a comma-separated list of one
or more of the following identifiers:
• crlf (map CR to LF),
• crcrlf (map CR to CR + LF),
• igncr (ignore CR),
• lfcr (map LF to CR),
• lfcrlf (map LF to CR + LF),
• ignlf (ignore LF),
• bsdel (map BS to DEL),
• delbs (map DEL to BS)
• spchex (map special chars (< 0x20 || 0x7f), excl. CR, LF, and TAB to hex)
• tabhex (map TAB to hex)
• crhex (map CR to hex)
• lfhex (map LF to hex)
• 8bithex (map chars with 8th-bit set to hex)
• nrmhex (map normal ascii chars (0x20 <= c < 0x7f) to hex)
The “to hex” mappings (???hex) replace the respective characters with their hexadecimal representation
(in square brackets), like this:
CR --> [0d]
If more than one mappings are provided that apply to the same character, then only the first mapping, in
the order listed above, is applied.
For example the command:
picocom --omap crlf,delbs --imap ignlf,bsdel --emap crcrlf ...
will:
• Replace every CR (carriage return, 0x0d) character with LF (line feed, 0x0a) and every DEL (delete,
0x7f) character with BS (backspace, 0x08) before writing it to the serial port.
• Ignore (not write to the terminal) every LF character read from the serial port, and replace every BS
character read from the serial port with DEL.
• Replace every CR character with CR and LF when echoing to the terminal (if local-echo is enabled).
EXITING PICOCOM
This section summarizes the conditions in which picocom terminates its operation and what happens in each
such condition:
• The exit command is seen in the standard input. That is, the escape character is seen (default C-a),
followed by the exit command character (default C-x). In this case: The contents of the output queue
(data read from the standard input, but not yet written to the port) as well as the contents of the O/S
serial port output buffer (data already written to the port, but not yet transmitted) are discarded
(flushed). Then the serial port is reset to it’s original settings, and the modem-control lines are
cleared signaling a modem reset, subject to the –noreset and the –hangup options. After that picocom
exits with a success status.
• The quit command is seen in the standard input. That is, the escape character is seen (default C-a),
followed by the quit command character (default C-q). The behavior in this case is similar to that of
the exit command, with one difference: Picocom behaves as if the –noreset option is given (regardless
if it actualy is, or not).
• The –exit option is given. See the documentation of this option for a description of what exactly
happens in this case. Picocom exits with a success exit status.
• The –exit-after option is given. See the documentation of this option for a description of what
exactly happens in this case. Picocom exits with a success exit status.
• Zero bytes are read from the standard input. This usually means that whatever was connected to
picocom’s standard input has been closed or, if a file was connected, then picocom has read up to the
end of the file. In this case, if the –exit-after option is not given, picocom stops reading from the
standard input, and keeps operating normally (i.e. writing to, and reading from, the serial port) until
its output queue empties. When this happens, picocom waits for the O/S serial port output buffer to
drain and then (subject to the –noreset and –hangup options) resets the serial port to it’s initial
settings, clears the modem-control lines, and exits. If the –exit-after option is given then, again,
picocom stops reading from the standard input and continues operating normally but, in this case, it
does so until it becomes idle for the specified amount of time, before exiting. Picocom exits with a
success exit status.
• Picocom is killed by the TERM or INT signal, or an unrecoverable error occurs. In this case picocom
behaves as if it had received the exit command, that is: The contents of the output queue and the
contents of the O/S serial port output buffer are discarded (flushed). Then, subject to the –noreset
and –hangup options, the serial port is reset to its original settings, the modem control lines are
cleared, and picocom exits with a failure status.
AUTHOR
Written by Nick Patavalis <npat@efault.net>
AVAILABILITY
Download the latest release from: <https://github.com/npat-efault/picocom/releases>
COPYRIGHT
Copyright (c) 2003-2018 Nick Patavalis
This file is part of Picocom.
Picocom is free software; you can redistribute it and/or modify it under the terms of the GNU General
Public License as published by the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
Picocom is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write
to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Picocom 3.1 PICOCOM(1)