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