Communications Monitor Window
JMRI provides a communications monitor window so you can see what's happening on the
communications link between the program and the layout hardware.
Once you open a monitor window, it will automatically display all traffic on the link as
long as "Filter Bytes" is blank.
- Clear Screen
- Erases the log area at the top of the screen
- Freeze Screen
- Stops acquiring new information, so that the captured information stops scrolling
- Show raw data
- Normally, the monitor displays the program's interpretation of what it's seeing. If you
want to see the raw bytes, check this box.
- Show timestamps
- Normally, the program just displays the data from the communication link. If you'd like
each message to be preceded by the time it was sent or received, check this box.
- Add message
- If you want to insert a message into the captured information, e.g. to make a note
about what you're about to do, you can type it into the text field next to the "Add
Message" button and then click that button. This is particularly useful when you're logging
to a file (see below) and want to make a note for later about what's happening.
- Filter Bytes
- You can filter unwanted messages from the window by entering each message's first hex
value into the "Filter Bytes" field. This can be especially helpful when there is a lot of
routine comm traffic. Separate multiple values by spaces. e.g. "B0 D0 CC". This example
will suppress any messages whose raw data starts with "B0", "D0" or "CC" You can determine
the available hex values by turning on "Show raw data."
Logging To A File
Sometimes, it's helpful to capture what's happening. For example, you might encounter a bug
(!!), and want to send a copy of what's happening to the people who are trying to fix it.
Small amounts of data can be copied from the log window with your computers "copy" command
(e.g. ctrl-C or cmd-C), and then pasted into an email.
If you want to capture more, you can have the window write a log file on your computer's
disk. To do this:
- Click "Choose log file". A file-chooser window will open. Navigate to where you want to
store the file, enter a name for the new log file, and click "Save". Note that if you pick
a file that already exists, it will be overwritten.
- When you're ready to capture the data you want, click "Start logging" on the monitor
- When you're done, click "Stop logging" to store the data and close the file.