M579 implemented. This allows any processor pin to be set or

read.  Obviously use setting with extreme caution.

Format:

M579 P31 S0

This sets processor pin 31 (whatever that might be) to a 0. Without the S field the command returns the state of the pin.

GCodes.cpp

@@ -4248,7 +4248,9 @@ bool GCodes::HandleMcode(GCodeBuffer* gb)
 			}
 			break;
 
-		case 578: // Fire Inkjet bits
+		// Fire Inkjet bits
+
+		case 578: 
 			if (!AllMovesAreFinishedAndMoveBufferIsLoaded())
 				return false;
 			if(gb->Seen('S')) // Need to handle the 'P' parameter too; see http://reprap.org/wiki/G-code#M578:_Fire_inkjet_bits
@@ -4312,8 +4314,8 @@ bool GCodes::HandleMcode(GCodeBuffer* gb)
 			}
 			break;
 
-			//****************************
-			// These last are M codes only for the cognoscenti
+//****************************
+// These last are M codes only for the cognoscenti
 
 		case 562: // Reset temperature fault - use with great caution
 			if (gb->Seen('P'))
@@ -4361,6 +4363,20 @@ bool GCodes::HandleMcode(GCodeBuffer* gb)
 			}
 			break;
 
+		// Set or read processor pins directly.  Setting should obviously be
+        // used with extreme caution.
+
+		case 579:
+			if(gb->Seen('P'))
+			{
+				int pin = gb->GetIValue();
+				if(gb->Seen('S'))
+					platform->SetOutputPin(pin, gb->GetIValue());
+				else
+					reply.printf("Pin %d is %s.\n", pin, platform->GetInputPin(pin) ? "high" : "low");
+			}
+			break;
+
 		case 999: // Restart after being stopped by error
 			result = DoDwellTime(0.5);		// wait half a second to allow the response to be sent back to the web server, otherwise it may retry
 			if (result)

Platform.h

@@ -736,6 +736,13 @@ class Platform
 		// So you can test for inkjet presence with if(platform->Inkjet(0))
 
 		bool Inkjet(int bitPattern);
+
+		// Two functions to set and get any processor pin.
+        // Only for use by the M579 command with extreme caution.  Don't use these
+        // for anything else.
+
+		void SetOutputPin(int pin, bool value);
+		bool GetInputPin(int pin);
 
 	private:
 		void ResetChannel(size_t chan); // re-initialise a serial channel
@@ -1302,6 +1309,22 @@ inline void Platform::SetNozzleDiameter(float diameter)
 	nozzleDiameter = diameter;
 }
 
+// Two functions to set and get any processor pin.
+// Only for use by the M579 command with extreme caution.  Don't use these
+// for anything else.
+
+inline void Platform::SetOutputPin(int pin, bool value)
+{
+	pinMode(pin, OUTPUT);
+	digitalWrite(pin, value);	
+}
+
+inline bool Platform::GetInputPin(int pin)
+{
+	return digitalRead(pin);
+}
+
+
 //***************************************************************************************
 
 #endif