add support for full-duplex comms with MOS

enables flow control if a GP command is received with value 2

video/vdp_protocol.h

@@ -16,12 +16,16 @@
 
 #define VDPSerial Serial2
 
+void setVDPProtocolDuplex(bool duplex) {
+	VDPSerial.setHwFlowCtrlMode(duplex ? HW_FLOWCTRL_CTS_RTS : HW_FLOWCTRL_RTS, 64);
+}
+
 void setupVDPProtocol() {
 	VDPSerial.end();
 	VDPSerial.setRxBufferSize(UART_RX_SIZE);					// Can't be called when running
 	VDPSerial.begin(UART_BR, SERIAL_8N1, UART_RX, UART_TX);
-	VDPSerial.setHwFlowCtrlMode(HW_FLOWCTRL_RTS, 64);			// Can be called whenever
 	VDPSerial.setPins(UART_NA, UART_NA, UART_CTS, UART_RTS);	// Must be called after begin
+	setVDPProtocolDuplex(false);								// Start with half-duplex
 	VDPSerial.setTimeout(COMMS_TIMEOUT);
 }
 

video/vdu_sys.h

@@ -350,6 +350,13 @@ void VDUStreamProcessor::sendGeneralPoll() {
 		debug_log("sendGeneralPoll: Timeout\n\r");
 		return;
 	}
+	if (b == 2) {
+		// Full duplex mode requested
+		setVDPProtocolDuplex(true);
+		// NB if an application is running on a MOS that _isn't_ set up for full duplex
+		// and happens to send a GP with a value 2 this will break comms with MOS
+		debug_log("Full duplex mode requested\n\r");
+	}
 	uint8_t packet[] = {
 		(uint8_t) (b & 0xFF),
 	};