picocom

PICOCOM(1) User Commands PICOCOM(1)

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.