diff --git a/Makefile b/Makefile
index 5cc6dd7..ef5b6fc 100644
--- a/Makefile
+++ b/Makefile
@@ -157,7 +157,7 @@ build/%.hex : build/%.elf
 
 .PHONY: flash
 flash: build/grbl.hex
-	fm COM(13, 115200) DEVICE(LPC1769, 0.000000, 0) HARDWARE(BOOTEXEC, 50, 100) ERASEUSED(build\grbl.hex, PROTECTISP) HEXFILE(build\grbl.hex, NOCHECKSUMS, NOFILL, PROTECTISP)
+	fm COM(15, 115200) DEVICE(LPC1769, 0.000000, 0) HARDWARE(BOOTEXEC, 50, 100) ERASEUSED(build\grbl.hex, PROTECTISP) HEXFILE(build\grbl.hex, NOCHECKSUMS, NOFILL, PROTECTISP)
 
 .PHONY: clean
 clean:
diff --git a/VCOM_lib/usbSerial.c b/VCOM_lib/usbSerial.c
index 1bddc1e..3be5257 100644
--- a/VCOM_lib/usbSerial.c
+++ b/VCOM_lib/usbSerial.c
@@ -86,6 +86,7 @@ static U8 txdata[VCOM_FIFO_SIZE];
 static fifo_t txfifo;
 //static fifo_t rxfifo;
 
+static UsbSerialLineStateCallback* usbSerialLineStateCallback = nullptr;
 static UsbSerialReadCallback* usbSerialReadCallback = nullptr;
 
 // forward declaration of interrupt handler
@@ -299,10 +300,13 @@ static BOOL HandleClassRequest(TSetupPacket *pSetup, int *piLen, U8 **ppbData)
 		break;
 
 	// set control line state
-	case SET_CONTROL_LINE_STATE:
-		// bit0 = DTR, bit = RTS
-
-		break;
+	case SET_CONTROL_LINE_STATE: {
+	    bool dtr = (pSetup->wValue >> 0) & 1;
+	    bool rts = (pSetup->wValue >> 1) & 1;
+	    if (usbSerialLineStateCallback)
+			usbSerialLineStateCallback(dtr, rts);
+	    break;
+	}
 
 	default:
 		return FALSE;
@@ -376,8 +380,9 @@ void enable_USB_interrupts(void);
 	main
 	====
 **************************************************************************/
-int usbSerialInit(UsbSerialReadCallback* usbSerialReadCallback)
+int usbSerialInit(UsbSerialLineStateCallback* usbSerialLineStateCallback, UsbSerialReadCallback* usbSerialReadCallback)
 {
+	::usbSerialLineStateCallback = usbSerialLineStateCallback;
 	::usbSerialReadCallback = usbSerialReadCallback;
 
 	// initialise stack
diff --git a/VCOM_lib/usbSerial.h b/VCOM_lib/usbSerial.h
index e05db60..3007a9e 100644
--- a/VCOM_lib/usbSerial.h
+++ b/VCOM_lib/usbSerial.h
@@ -98,10 +98,13 @@ void VCOM_gets_echo(char *str); // gets string terminated in '\r' or '\n' and ec
 
 #include "serial_fifo.h"
 
+// Receives line state. Called by an interrupt.
+typedef void UsbSerialLineStateCallback(bool dtr, bool rts);
+
 // Receives serial data. Called by an interrupt.
 typedef void UsbSerialReadCallback(const U8* data, unsigned len);
 
-int usbSerialInit(UsbSerialReadCallback* usbSerialReadCallback); // run once in main b4 main loop starts.
+int usbSerialInit(UsbSerialLineStateCallback* usbSerialLineStateCallback, UsbSerialReadCallback* usbSerialReadCallback); // run once in main b4 main loop starts.
 
 /*
 	Writes one character to VCOM port
diff --git a/grbl/serial.c b/grbl/serial.c
index 9e1fa1b..85eff99 100644
--- a/grbl/serial.c
+++ b/grbl/serial.c
@@ -49,6 +49,8 @@ void serialInterrupt(uint32_t event);
 void legacy_ISR(uint8_t data);
 uint8_t arm_rx_buf[1];
 
+bool lastDtr = false;
+
 // Returns the number of bytes available in the RX serial buffer.
 uint16_t serial_get_rx_buffer_available()
 {
@@ -80,10 +82,18 @@ uint8_t serial_get_tx_buffer_count()
 void serial_init()
 {
 #ifdef USE_USB
-  usbSerialInit([](const U8* data, unsigned len) {
-    while(len--)
-      legacy_ISR(*data++);
-  });
+  usbSerialInit(
+    [](bool dtr, bool rts) {
+      if (dtr != lastDtr)
+      {
+        lastDtr = dtr;
+        mc_reset();
+      }
+    },
+    [](const U8* data, unsigned len) {
+      while (len--)
+        legacy_ISR(*data++);
+    });
 #else
   int32_t uartFlags = ARM_USART_MODE_ASYNCHRONOUS |
                       ARM_USART_DATA_BITS_8 |