Add opendrain option to Serial#.setTX

teensy3/HardwareSerial.h

 void serial_end(void);
 void serial_set_transmit_pin(uint8_t pin);
 void serial_set_rx(uint8_t pin);
-void serial_set_tx(uint8_t pin);
+void serial_set_tx(uint8_t pin, uint8_t opendrain);
 int serial_set_rts(uint8_t pin);
 int serial_set_cts(uint8_t pin);
 void serial_putchar(uint32_t c);
 void serial2_end(void);
 void serial2_set_transmit_pin(uint8_t pin);
 void serial2_set_rx(uint8_t pin);
-void serial2_set_tx(uint8_t pin);
+void serial2_set_tx(uint8_t pin, uint8_t opendrain);
 int serial2_set_rts(uint8_t pin);
 int serial2_set_cts(uint8_t pin);
 void serial2_putchar(uint32_t c);
 void serial3_end(void);
 void serial3_set_transmit_pin(uint8_t pin);
 void serial3_set_rx(uint8_t pin);
-void serial3_set_tx(uint8_t pin);
+void serial3_set_tx(uint8_t pin, uint8_t opendrain);
 int serial3_set_rts(uint8_t pin);
 int serial3_set_cts(uint8_t pin);
 void serial3_putchar(uint32_t c);
 	virtual void end(void)		{ serial_end(); }
 	virtual void transmitterEnable(uint8_t pin) { serial_set_transmit_pin(pin); }
 	virtual void setRX(uint8_t pin) { serial_set_rx(pin); }
-	virtual void setTX(uint8_t pin) { serial_set_tx(pin); }
+	virtual void setTX(uint8_t pin, bool opendrain=false) { serial_set_tx(pin, opendrain); }
 	virtual bool attachRts(uint8_t pin) { return serial_set_rts(pin); }
 	virtual bool attachCts(uint8_t pin) { return serial_set_cts(pin); }
 	virtual int available(void)     { return serial_available(); }
 	virtual void end(void)		{ serial2_end(); }
 	virtual void transmitterEnable(uint8_t pin) { serial2_set_transmit_pin(pin); }
 	virtual void setRX(uint8_t pin) { serial2_set_rx(pin); }
-	virtual void setTX(uint8_t pin) { serial2_set_tx(pin); }
+	virtual void setTX(uint8_t pin, bool opendrain=false) { serial2_set_tx(pin, opendrain); }
 	virtual bool attachRts(uint8_t pin) { return serial2_set_rts(pin); }
 	virtual bool attachCts(uint8_t pin) { return serial2_set_cts(pin); }
 	virtual int available(void)     { return serial2_available(); }
 	virtual void end(void)          { serial3_end(); }
 	virtual void transmitterEnable(uint8_t pin) { serial3_set_transmit_pin(pin); }
 	virtual void setRX(uint8_t pin) { serial3_set_rx(pin); }
-	virtual void setTX(uint8_t pin) { serial3_set_tx(pin); }
+	virtual void setTX(uint8_t pin, bool opendrain=false) { serial3_set_tx(pin, opendrain); }
 	virtual bool attachRts(uint8_t pin) { return serial3_set_rts(pin); }
 	virtual bool attachCts(uint8_t pin) { return serial3_set_cts(pin); }
 	virtual int available(void)     { return serial3_available(); }

teensy3/serial1.c

 	#endif
 }
 
-void serial_set_tx(uint8_t pin)
+void serial_set_tx(uint8_t pin, uint8_t opendrain)
 {
+	uint32_t cfg;
+
+	if (opendrain) pin |= 128;
 	if (pin == tx_pin_num) return;
 	if ((SIM_SCGC4 & SIM_SCGC4_UART0)) {
-		switch (tx_pin_num) {
+		switch (tx_pin_num & 127) {
 			case 1:  CORE_PIN1_CONFIG = 0; break; // PTB17
 			case 5:  CORE_PIN5_CONFIG = 0; break; // PTD7
 			#if defined(KINETISL)
 			case 4:  CORE_PIN4_CONFIG = 0; break; // PTA2
 			#endif
 		}
-		switch (pin) {
-			case 1:  CORE_PIN1_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
-			case 5:  CORE_PIN5_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
+		if (opendrain) {
+			cfg = PORT_PCR_DSE | PORT_PCR_ODE;
+		} else {
+			cfg = PORT_PCR_DSE | PORT_PCR_SRE;
+		}
+		switch (pin & 127) {
+			case 1:  CORE_PIN1_CONFIG = cfg | PORT_PCR_MUX(3); break;
+			case 5:  CORE_PIN5_CONFIG = cfg | PORT_PCR_MUX(3); break;
 			#if defined(KINETISL)
-			case 4:  CORE_PIN4_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(2); break;
+			case 4:  CORE_PIN4_CONFIG = cfg | PORT_PCR_MUX(2); break;
 			#endif
 		}
 	}

teensy3/serial2.c

 	#endif
 }
 
-void serial2_set_tx(uint8_t pin)
+void serial2_set_tx(uint8_t pin, uint8_t opendrain)
 {
 	#if defined(KINETISK)
+	uint32_t cfg;
+
+	if (opendrain) pin |= 128;
 	if (pin == tx_pin_num) return;
 	if ((SIM_SCGC4 & SIM_SCGC4_UART2)) {
-		switch (tx_pin_num) {
+		switch (tx_pin_num & 127) {
 			case 10: CORE_PIN10_CONFIG = 0; break; // PTC4
 			case 31: CORE_PIN31_CONFIG = 0; break; // PTE0
 		}
-		switch (pin) {
-			case 10: CORE_PIN10_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
-			case 31: CORE_PIN31_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
+		if (opendrain) {
+			cfg = PORT_PCR_DSE | PORT_PCR_ODE;
+		} else {
+			cfg = PORT_PCR_DSE | PORT_PCR_SRE;
+		}
+		switch (pin & 127) {
+			case 10: CORE_PIN10_CONFIG = cfg | PORT_PCR_MUX(3); break;
+			case 31: CORE_PIN31_CONFIG = cfg | PORT_PCR_MUX(3); break;
 		}
 	}
 	tx_pin_num = pin;

teensy3/serial3.c

 	#endif
 }
 
-void serial3_set_tx(uint8_t pin)
+void serial3_set_tx(uint8_t pin, uint8_t opendrain)
 {
 	#if defined(KINETISL)
+	uint32_t cfg;
+
+	if (opendrain) pin |= 128;
 	if (pin == tx_pin_num) return;
 	if ((SIM_SCGC4 & SIM_SCGC4_UART2)) {
-		switch (tx_pin_num) {
+		switch (tx_pin_num & 127) {
 			case 8:  CORE_PIN8_CONFIG = 0; break; // PTD3
 			case 20: CORE_PIN20_CONFIG = 0; break; // PTD5
 		}
-		switch (pin) {
-			case 8:  CORE_PIN8_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
-			case 20: CORE_PIN20_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3); break;
+		if (opendrain) {
+			cfg = PORT_PCR_DSE | PORT_PCR_ODE;
+		} else {
+			cfg = PORT_PCR_DSE | PORT_PCR_SRE;
+		}
+		switch (pin & 127) {
+			case 8:  CORE_PIN8_CONFIG = cfg | PORT_PCR_MUX(3); break;
+			case 20: CORE_PIN20_CONFIG = cfg | PORT_PCR_MUX(3); break;
 		}
 	}
 	tx_pin_num = pin;