Add sp_start_break() and sp_end_break() functions.

libserialport.h.in

@@ -534,6 +534,28 @@ enum sp_return sp_flush(struct sp_port *port, enum sp_buffer buffers);
  */
 enum sp_return sp_drain(struct sp_port *port);
 
+/**
+ * @}
+ * @defgroup Signal Port signalling operations
+ * @{
+ */
+
+/**
+ * Put the port transmit line into the break state.
+ *
+ * @return SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
+ *         if an invalid port is passed.
+ */
+enum sp_return sp_start_break(struct sp_port *port);
+
+/**
+ * Take the port transmit line out of the break state.
+ *
+ * @return SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
+ *         if an invalid port is passed.
+ */
+enum sp_return sp_end_break(struct sp_port *port);
+
 /**
  * @}
  * @defgroup Errors Obtaining error information

serialport.c

@@ -1298,6 +1298,34 @@ enum sp_return sp_set_flowcontrol(struct sp_port *port, enum sp_flowcontrol flow
 	return SP_OK;
 }
 
+enum sp_return sp_start_break(struct sp_port *port)
+{
+	CHECK_PORT();
+#ifdef _WIN32
+	if (SetCommBreak(port->hdl) == 0)
+		return SP_ERR_FAIL;
+#else
+	if (ioctl(port->fd, TIOCSBRK, 1) < 0)
+		return SP_ERR_FAIL;
+#endif
+
+	return SP_OK;
+}
+
+enum sp_return sp_end_break(struct sp_port *port)
+{
+	CHECK_PORT();
+#ifdef _WIN32
+	if (ClearCommBreak(port->hdl) == 0)
+		return SP_ERR_FAIL;
+#else
+	if (ioctl(port->fd, TIOCCBRK, 1) < 0)
+		return SP_ERR_FAIL;
+#endif
+
+	return SP_OK;
+}
+
 int sp_last_error_code(void)
 {
 #ifdef _WIN32