Add transmitterEnable on Serial2 & Serial3

teensy3/HardwareSerial.h

 void serial2_begin(uint32_t divisor);
 void serial2_format(uint32_t format);
 void serial2_end(void);
+void serial2_set_transmit_pin(uint8_t pin);
 void serial2_putchar(uint32_t c);
 void serial2_write(const void *buf, unsigned int count);
 void serial2_flush(void);
 void serial3_begin(uint32_t divisor);
 void serial3_format(uint32_t format);
 void serial3_end(void);
+void serial3_set_transmit_pin(uint8_t pin);
 void serial3_putchar(uint32_t c);
 void serial3_write(const void *buf, unsigned int count);
 void serial3_flush(void);
 					  serial2_begin(BAUD2DIV(baud));
 					  serial2_format(format); }
 	virtual void end(void)		{ serial2_end(); }
+	virtual void transmitterEnable(uint8_t pin) { serial2_set_transmit_pin(pin); }
 	virtual int available(void)     { return serial2_available(); }
 	virtual int peek(void)          { return serial2_peek(); }
 	virtual int read(void)          { return serial2_getchar(); }
 					  serial3_begin(BAUD2DIV3(baud));
 					  serial3_format(format); }
 	virtual void end(void)          { serial3_end(); }
+	virtual void transmitterEnable(uint8_t pin) { serial3_set_transmit_pin(pin); }
 	virtual int available(void)     { return serial3_available(); }
 	virtual int peek(void)          { return serial3_peek(); }
 	virtual int read(void)          { return serial3_getchar(); }

teensy3/serial2.c

 static volatile BUFTYPE tx_buffer[TX_BUFFER_SIZE];
 static volatile BUFTYPE rx_buffer[RX_BUFFER_SIZE];
 static volatile uint8_t transmitting = 0;
+static volatile uint8_t *transmit_pin=NULL;
 #if TX_BUFFER_SIZE > 255
 static volatile uint16_t tx_buffer_head = 0;
 static volatile uint16_t tx_buffer_tail = 0;
 	rx_buffer_tail = 0;
 }
 
+void serial2_set_transmit_pin(uint8_t pin)
+{
+	while (transmitting) ;
+	pinMode(pin, OUTPUT);
+	digitalWrite(pin, LOW);
+	transmit_pin = portOutputRegister(pin);
+}
+
 void serial2_putchar(uint32_t c)
 {
 	uint32_t head, n;
 
 	if (!(SIM_SCGC4 & SIM_SCGC4_UART1)) return;
+	if (transmit_pin) *transmit_pin = 1;
 	head = tx_buffer_head;
 	if (++head >= TX_BUFFER_SIZE) head = 0;
 	while (tx_buffer_tail == head) {
         uint32_t head, n;
 
 	if (!(SIM_SCGC4 & SIM_SCGC4_UART1)) return;
+	if (transmit_pin) *transmit_pin = 1;
 	while (p < end) {
 		head = tx_buffer_head;
 		if (++head >= TX_BUFFER_SIZE) head = 0;
 #endif
 	if ((c & UART_C2_TCIE) && (UART1_S1 & UART_S1_TC)) {
 		transmitting = 0;
+		if (transmit_pin) *transmit_pin = 0;
 		UART1_C2 = C2_TX_INACTIVE;
 	}
 }

teensy3/serial3.c

 static volatile BUFTYPE tx_buffer[TX_BUFFER_SIZE];
 static volatile BUFTYPE rx_buffer[RX_BUFFER_SIZE];
 static volatile uint8_t transmitting = 0;
+static volatile uint8_t *transmit_pin=NULL;
 #if TX_BUFFER_SIZE > 255
 static volatile uint16_t tx_buffer_head = 0;
 static volatile uint16_t tx_buffer_tail = 0;
 	rx_buffer_tail = 0;
 }
 
+void serial3_set_transmit_pin(uint8_t pin)
+{
+	while (transmitting) ;
+	pinMode(pin, OUTPUT);
+	digitalWrite(pin, LOW);
+	transmit_pin = portOutputRegister(pin);
+}
+
 void serial3_putchar(uint32_t c)
 {
 	uint32_t head;
 
 	if (!(SIM_SCGC4 & SIM_SCGC4_UART2)) return;
+	if (transmit_pin) *transmit_pin = 1;
 	head = tx_buffer_head;
 	if (++head >= TX_BUFFER_SIZE) head = 0;
 	while (tx_buffer_tail == head) {
 	uint32_t head, tail, n;
 	uint8_t c;
 
-	//digitalWriteFast(4, HIGH);
 	if (UART2_S1 & UART_S1_RDRF) {
-		//digitalWriteFast(5, HIGH);
 		n = UART2_D;
 		if (use9Bits && (UART2_C3 & 0x80)) n |= 0x100;
 		head = rx_buffer_head + 1;
 			rx_buffer[head] = n;
 			rx_buffer_head = head; 
 		}
-		//digitalWriteFast(5, LOW);
 	}
 	c = UART2_C2;
 	if ((c & UART_C2_TIE) && (UART2_S1 & UART_S1_TDRE)) {
-		//digitalWriteFast(5, HIGH);
 		head = tx_buffer_head;
 		tail = tx_buffer_tail;
 		if (head == tail) {
 			UART2_D = n;
 			tx_buffer_tail = tail;
 		}
-		//digitalWriteFast(5, LOW);
 	}
 	if ((c & UART_C2_TCIE) && (UART2_S1 & UART_S1_TC)) {
 		transmitting = 0;
+		if (transmit_pin) *transmit_pin = 0;
 		UART2_C2 = C2_TX_INACTIVE;
 	}
-	//digitalWriteFast(4, LOW);
 }