Improved the checksumming speed by a factor of 1.4-3.4

AUTHORS.md

@@ -85,6 +85,7 @@ date of first contribution):
   * [Luke McKechnie](https://github.com/galamdring)
   * [Peter Backx](https://github.com/pbackx)
   * [Josh Major](https://github.com/astateofblank)
+  * ["alex-gh"](https://github.com/alex-gh)
 
 OctoPrint started off as a fork of [Cura](https://github.com/daid/Cura) by
 [Daid Braam](https://github.com/daid). Parts of its communication layer and

src/octoprint/util/comm.py

@@ -2472,8 +2472,8 @@ class MachineCom(object):
 	def _do_send_with_checksum(self, command, linenumber):
 		command_to_send = "N" + str(linenumber) + " " + command
 		checksum = 0
-		for c in command_to_send:
-			checksum ^= ord(c)
+		for c in bytearray(command_to_send):
+			checksum ^= c
 		command_to_send = command_to_send + "*" + str(checksum)
 		self._do_send_without_checksum(command_to_send)