From 0279aafb970537a4120c54b3e7a84195250c302f Mon Sep 17 00:00:00 2001
From: Armin Wolf <W_Armin@gmx.de>
Date: Fri, 1 Sep 2023 21:18:25 +0200
Subject: [PATCH] Allow for setting DTR on a serial port

---
 serial_port/serial_port.cpp | 47 +++++++++++++++++++++++++++++++++++++
 serial_port/serial_port.h   |  1 +
 2 files changed, 48 insertions(+)

diff --git a/serial_port/serial_port.cpp b/serial_port/serial_port.cpp
index b8d60310..8113f5c9 100644
--- a/serial_port/serial_port.cpp
+++ b/serial_port/serial_port.cpp
@@ -660,6 +660,53 @@ void serial_port::serial_break()
 #endif
 }
 
+void serial_port::serial_set_dtr(bool dtr)
+{
+    /*-----------------------------------------------------*\
+    | Windows-specific code path for serial set DTR         |
+    \*-----------------------------------------------------*/
+#ifdef _WIN32
+    if(dtr)
+    {
+        EscapeCommFunction(file_descriptor, SETDTR);
+    }
+    else
+    {
+        EscapeCommFunction(file_descriptor, CLRDTR);
+    }
+#endif
+
+    /*-----------------------------------------------------*\
+    | Linux-specific code path for serial set DTR           |
+    \*-----------------------------------------------------*/
+#ifdef __linux__
+    const int DTRFLAG = TIOCM_DTR;
+    if(dtr)
+    {
+        ioctl(file_descriptor, TIOCMBIS, &DTRFLAG);
+    }
+    else
+    {
+        ioctl(file_descriptor, TIOCMBIC, &DTRFLAG);
+    }
+#endif
+
+    /*-----------------------------------------------------*\
+    | MacOS-specific code path for serial set DTR           |
+    \*-----------------------------------------------------*/
+#ifdef __APPLE__
+    const int DTRFLAG = TIOCM_DTR;
+    if(dtr)
+    {
+        ioctl(file_descriptor, TIOCMBIS, &DTRFLAG);
+    }
+    else
+    {
+        ioctl(file_descriptor, TIOCMBIC, &DTRFLAG);
+    }
+#endif
+}
+
 void serial_port::serial_set_rts(bool rts)
 {
     /*-----------------------------------------------------*\
diff --git a/serial_port/serial_port.h b/serial_port/serial_port.h
index 0d60b162..191120cf 100644
--- a/serial_port/serial_port.h
+++ b/serial_port/serial_port.h
@@ -126,6 +126,7 @@ public:
     void serial_flush_tx();
     void serial_break();
 
+    void serial_set_dtr(bool dtr);
     void serial_set_rts(bool rts);
 
     int serial_available();