Improved script docs and script usage description in README.md

Also introduced graceful error handling when trying to access
interactive mode on Windows.

README.md

@@ -17,6 +17,31 @@ The folder "utils" contains utility scripts for working with masterMacs motor co
 - decodeError.py: Take the return message of a R11 (read error) command and print it in human-readable form.
 - writeRead.py: Send messages to the controller and receive answers.
 
+These scripts can be run from anywhere. On Linux, the shebang (#!) automatically
+calls the system Python 3 executable:
+
+```bash
+# To show the help, use either flag -h or --help (works on all scripts)
+/path/to/mastermacs_repo/utils/decodeStatus.py -h 
+/path/to/mastermacs_repo/utils/decodeError.py --help
+/path/to/mastermacs_repo/utils/writeRead.py -h
+
+# To run in non-interactive mode, give the value as an argument
+/path/to/mastermacs_repo/utils/decodeStatus.py 1234
+/path/to/mastermacs_repo/utils/decodeError.py 5678
+/path/to/mastermacs_repo/utils/writeRead.py "R11"
+
+# To run in interactive mode, don't give any argument. This only works on Linux
+/path/to/mastermacs_repo/utils/decodeStatus.py
+/path/to/mastermacs_repo/utils/decodeError.py
+/path/to/mastermacs_repo/utils/writeRead.py
+```
+
+To use these scripts on Windows, prefix the Python 3 executable:
+```bash
+C:/path/to/python3.exe C:/path/to/mastermacs_repo/utils/decodeStatus.py 1234
+```
+
 ## Developer guide
 
 ### Usage in IOC shell