From 2007b623c9457ecb1b15397f41d632f911b4461e Mon Sep 17 00:00:00 2001
From: Sandeep Mistry <s.mistry@arduino.cc>
Date: Tue, 17 Nov 2015 09:53:52 -0500
Subject: [PATCH 1/3] Add CDC_SEND_BREAK define

---
 hardware/arduino/sam/cores/arduino/USB/USBCore.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hardware/arduino/sam/cores/arduino/USB/USBCore.h b/hardware/arduino/sam/cores/arduino/USB/USBCore.h
index 893d84fcbbe..465c71de1d5 100644
--- a/hardware/arduino/sam/cores/arduino/USB/USBCore.h
+++ b/hardware/arduino/sam/cores/arduino/USB/USBCore.h
@@ -55,6 +55,7 @@
 #define CDC_SET_LINE_CODING			0x20
 #define CDC_GET_LINE_CODING			0x21
 #define CDC_SET_CONTROL_LINE_STATE	0x22
+#define CDC_SEND_BREAK				0x23
 
 #define MSC_RESET					0xFF
 #define MSC_GET_MAX_LUN				0xFE

From 86e34b99401679e1790bf8fedc7df13f5f3dd4e3 Mon Sep 17 00:00:00 2001
From: Sandeep Mistry <s.mistry@arduino.cc>
Date: Tue, 17 Nov 2015 09:57:04 -0500
Subject: [PATCH 2/3] Support receiving a USB CDC SEND_BREAK

---
 hardware/arduino/sam/cores/arduino/USB/CDC.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hardware/arduino/sam/cores/arduino/USB/CDC.cpp b/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
index 306c124ff24..9ab8356d92f 100644
--- a/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
+++ b/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
@@ -141,6 +141,11 @@ bool WEAK CDC_Setup(USBSetup& setup)
 			}
 			return true;
 		}
+
+		if (CDC_SEND_BREAK == r)
+		{
+			return true;
+		}
 	}
 	return false;
 }

From 9759f2cc607a1d65eccb49e5271cb686b99442e3 Mon Sep 17 00:00:00 2001
From: Sandeep Mistry <s.mistry@arduino.cc>
Date: Tue, 17 Nov 2015 10:09:56 -0500
Subject: [PATCH 3/3] Port AVR Serial_::readBreak() API to SAM core

---
 .../arduino/sam/cores/arduino/USB/CDC.cpp     | 25 +++++++++++++++++++
 .../arduino/sam/cores/arduino/USB/USBAPI.h    | 17 +++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/hardware/arduino/sam/cores/arduino/USB/CDC.cpp b/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
index 9ab8356d92f..1df3061e3ed 100644
--- a/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
+++ b/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
@@ -55,6 +55,8 @@ static volatile LineInfo _usbLineInfo = {
     0x00   // lineState
 };
 
+static volatile int32_t breakValue = -1;
+
 _Pragma("pack(1)")
 static const CDCDescriptor _cdcInterface =
 {
@@ -144,6 +146,7 @@ bool WEAK CDC_Setup(USBSetup& setup)
 
 		if (CDC_SEND_BREAK == r)
 		{
+			breakValue = ((uint16_t)setup.wValueH << 8) | setup.wValueL;
 			return true;
 		}
 	}
@@ -305,6 +308,28 @@ Serial_::operator bool()
 	return result;
 }
 
+int32_t Serial_::readBreak() {
+	uint8_t enableInterrupts = ((__get_PRIMASK() & 0x1) == 0 && 
+								(__get_FAULTMASK() & 0x1) == 0);
+
+	// disable interrupts,
+	// to avoid clearing a breakValue that might occur 
+	// while processing the current break value
+	__disable_irq();
+
+	int ret = breakValue;
+
+	breakValue = -1;
+
+	if (enableInterrupts)
+	{
+		// re-enable the interrupts
+		__enable_irq();
+	}
+
+	return ret;
+}
+
 unsigned long Serial_::baud() {
 	return _usbLineInfo.dwDTERate;
 }
diff --git a/hardware/arduino/sam/cores/arduino/USB/USBAPI.h b/hardware/arduino/sam/cores/arduino/USB/USBAPI.h
index dbc2ec5dc61..2eeaca08e88 100644
--- a/hardware/arduino/sam/cores/arduino/USB/USBAPI.h
+++ b/hardware/arduino/sam/cores/arduino/USB/USBAPI.h
@@ -63,6 +63,23 @@ class Serial_ : public Stream
 	using Print::write; // pull in write(str) from Print
 	operator bool();
 
+	// This method allows processing "SEND_BREAK" requests sent by
+	// the USB host. Those requests indicate that the host wants to
+	// send a BREAK signal and are accompanied by a single uint16_t
+	// value, specifying the duration of the break. The value 0
+	// means to end any current break, while the value 0xffff means
+	// to start an indefinite break.
+	// readBreak() will return the value of the most recent break
+	// request, but will return it at most once, returning -1 when
+	// readBreak() is called again (until another break request is
+	// received, which is again returned once).
+	// This also mean that if two break requests are received
+	// without readBreak() being called in between, the value of the
+	// first request is lost.
+	// Note that the value returned is a long, so it can return
+	// 0-0xffff as well as -1.
+	int32_t readBreak();
+
 	// These return the settings specified by the USB host for the
 	// serial port. These aren't really used, but are offered here
 	// in case a sketch wants to act on these settings.