Don't flood the printer with temperature requests while says it is busy

Fixes #3994

plugins/USBPrinting/USBPrinterOutputDevice.py

@@ -74,6 +74,7 @@ class USBPrinterOutputDevice(PrinterOutputDevice):
         self._accepts_commands = True
 
         self._paused = False
+        self._printer_busy = False # when printer is preheating and waiting (M190/M109), or when waiting for action on the printer
 
         self._firmware_view = None
         self._firmware_location = None
@@ -320,8 +321,9 @@ class USBPrinterOutputDevice(PrinterOutputDevice):
                 # Timeout, or no request has been sent at all.
                 self._command_received.set() # We haven't really received the ok, but we need to send a new command
 
-                self.sendCommand("M105")
-                self._last_temperature_request = time()
+                if not self._printer_busy: # don't flood the printer with temperature requests while it is busy
+                    self.sendCommand("M105")
+                    self._last_temperature_request = time()
 
                 if self._firmware_name is None:
                     self.sendCommand("M115")
@@ -360,7 +362,9 @@ class USBPrinterOutputDevice(PrinterOutputDevice):
             if b"FIRMWARE_NAME:" in line:
                 self._setFirmwareName(line)
 
-            if b"ok" in line:
+            if line.startswith(b"ok "):
+                self._printer_busy = False
+
                 self._command_received.set()
                 if not self._command_queue.empty():
                     self._sendCommand(self._command_queue.get())
@@ -370,16 +374,19 @@ class USBPrinterOutputDevice(PrinterOutputDevice):
                     else:
                         self._sendNextGcodeLine()
 
+            if line.startswith(b"echo:busy: "):
+                self._printer_busy = True
+
             if self._is_printing:
                 if line.startswith(b'!!'):
                     Logger.log('e', "Printer signals fatal error. Cancelling print. {}".format(line))
                     self.cancelPrint()
-                elif b"resend" in line.lower() or b"rs" in line:
+                elif line.lower().startswith(b"resend") or line.startswith(b"rs"):
                     # A resend can be requested either by Resend, resend or rs.
                     try:
                         self._gcode_position = int(line.replace(b"N:", b" ").replace(b"N", b" ").replace(b":", b" ").split()[-1])
                     except:
-                        if b"rs" in line:
+                        if line.startswith(b"rs"):
                             # In some cases of the RS command it needs to be handled differently.
                             self._gcode_position = int(line.split()[1])