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emacs: send break on serial port

From: Cédric Chépied
Subject: emacs: send break on serial port
Date: Tue, 10 Jun 2014 08:59:20 +0200
User-agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (Gojō) APEL/10.8 Emacs/24.3 (x86_64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO)


I'm using serial-term to open a serial connection with devices and I sometimes
need to send a break. This is very useful for sysrq keys on embedded Linux
systems. I can't find how to do this inside emacs so I need to use minicom.

Will this functionality be added in emacs? I started to write it but I don't
know emacs code at all (I only write lisp) so any advice is welcome. This code
will only work on Linux:

0b6ff13ef78daf8aadeeb8f74e6ae91a6cbec47c HEAD master
Author: Cédric Chépied <address@hidden>
Date:   Mon Jun 9 15:53:06 2014 +0200

    Add a function to send a break via serial process
    This is useful to use sysrq keys.

1 file changed, 17 insertions(+)
 src/process.c | 17 +++++++++++++++++

        Modified   src/process.c
diff --git a/src/process.c b/src/process.c
index b8b8eaa..ef24b88 100644
--- a/src/process.c
+++ b/src/process.c
@@ -844,6 +844,22 @@ record_deleted_pid (pid_t pid, Lisp_Object filename)
+DEFUN ("send-break-process", Fsend_break_process, Ssend_break_process, 1, 1, 0,
+       doc: /* Send a break to a serial process. */)
+  (register Lisp_Object process)
+  register struct Lisp_Process *p;
+  process = get_process (process);
+  p = XPROCESS (process);
+  if (SERIALCONN1_P (p) && p->outfd >= 0)
+         ioctl(p->outfd, TCSBRK, 0);
+  return Qnil;
 DEFUN ("delete-process", Fdelete_process, Sdelete_process, 1, 1, 0,
        doc: /* Delete PROCESS: kill it and forget about it immediately.
 PROCESS may be a process, a buffer, the name of a process or buffer, or
@@ -7320,6 +7336,7 @@ The variable takes effect when `start-process' is called. 
   defsubr (&Sprocessp);
   defsubr (&Sget_process);
+  defsubr (&Ssend_break_process);
   defsubr (&Sdelete_process);
   defsubr (&Sprocess_status);
   defsubr (&Sprocess_exit_status);

Cédric Chépied

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