Merge pull request #425 from blurfl/Add-G4-gcode

Add G4 gcode, use maslowDelay() to remain responsive to GC during dwell time

cnc_ctrl_v1/GCode.cpp

@@ -345,6 +345,9 @@ void  executeGcodeLine(const String& gcodeLine){
             G2(gcodeLine, gNumber);
             sys.lastGCommand = gNumber;    // remember G number for next time
             break;
+        case 4:
+            G4(gcodeLine);
+            break;
         case 10:
             G10(gcodeLine);
             break;
@@ -698,6 +701,35 @@ void G2(const String& readString, int G2orG3){
     }
 }
 
+void  G4(const String& readString){
+    /*
+      The G4() dwell function handles the G4 gcode which pauses for P milliseconds or S seconds.
+      Only one of the two is accepted, the other ignored.
+      Use maslowDelay() to remain responsive to GC during the dwell time.
+      Because maslowDelay() operates in milliseconds, round to the nearest millisecond.
+      Negative values are treated as positive (not a time machine).
+    */
+    float dwellMS = abs(extractGcodeValue(readString, 'P', 0));
+    float dwellS  = abs(extractGcodeValue(readString, 'S', 0));
+
+    if (dwellMS == 0) {
+      /*
+        ignore S parameter unless P is zero
+      */
+      dwellMS = dwellS * 1000;
+    }
+    dwellMS = long(dwellMS + .5);
+    Serial.print(F("dwell time "));
+    if (dwellS > 0) {
+      Serial.print(dwellS);
+      Serial.println(F(" seconds"));
+    } else {
+      Serial.print(dwellMS, 0);
+      Serial.println(F(" ms."));
+    }
+    maslowDelay(dwellMS);
+}
+
 void  G10(const String& readString){
     /*The G10() function handles the G10 gcode which re-zeros one or all of the machine's axes.*/
     float currentZPos = zAxis.read();

cnc_ctrl_v1/GCode.h

@@ -40,6 +40,7 @@ void  sanitizeCommandString(String&);
 byte  interpretCommandString(String&);
 void  G1(const String&, int);
 void  G2(const String&, int);
+void  G4(const String&);
 void  G10(const String&);
 void  G38(const String&);
 void  setInchesToMillimetersConversion(float);