Add some more docs to the OSD tester.

python/osd_test.py

@@ -1,4 +1,9 @@
-import time
+#
+# To use this program to send OSD messages to HDZero googles for example.
+# 1. Ensure the VRX backpack (HDZero goggles backpack) is flashed with the latest version of it's backpack.
+# 2. Flash an ESP32 device using "DEBUG_ESP32_TX_Backpack_via_UART" or similar TX backpack.
+# 3. Run this python program and send commands.
+
 import serial
 import argparse
 import serials_find
@@ -46,13 +51,18 @@ def thread_function(s: serial.Serial):
 
 def help():
   print("Command should be one of:")
-  print("C = clear")
-  print("D = display all previously sent messages")
-  print("<row> <col> <message> = send message to OSD")
+  print("C = clear the OSD canvas")
+  print("D = display the OSD canvas")
+  print("<row> <col> <message> = send message to OSD canvas")
+  print()
+  print("Example:")
+  print("C")
+  print("10 10 ELRS Rocks")
+  print("D")
 
 if __name__ == '__main__':
   parser = argparse.ArgumentParser(
-    description="Initialize EdgeTX passthrough to internal module")
+    description="Send OSD messages to a VRX backpack via a TX backpack connected to a Serial port")
   parser.add_argument("-b", "--baud", type=int, default=460800,
     help="Baud rate for passthrough communication")
   parser.add_argument("-p", "--port", type=str,