Things are starting to come together quite nicely with JeeMon – all in less than 1000 lines of Tcl code so far. That’s not to say that it’s perfect yet – I’m still massively rearranging some of these code structures – but there is already some functionality to play with, which helps expose the strengths and weaknesses so far.

The basic approach is declarative in nature: specifying what should happen, but not necessarily in the same place as when or how all the work should be done.

Here’s my first tentative configuration file:

For each serial interface, an action is specified when that interface comes on-line. For example I can now plug in my A8007Up6 device (a USB-BUB with a JeeNode) and JeeMon will open a terminal window showing the output stream. Unplugging closes the window again (and automatically cleans everything up).

Right now, I’m editing this config file by hand, but at some point that could be augmented with a set of GUI or web-based configuration panels (even remotely).

There are a lot of challenges ahead. One of them is decoupling things so that code and data end up organized in the most convenient, logical, and flexible way. I’m trying very hard to avoid any calls to the “Config” module from generic JeeMon code. This allows you to set up the configuration file structure and hierarchy in any way you like.

My application file currently looks as follows:

As you can see, I’m setting up a periodic port scanner and supplying a “SerialEvent” callback to decide what to do when serial ports get added or removed. In those decisions, most of the logic is driven from the “config.txt” configuration file. I’m about to implement a similar callback for radio events, i.e. RF12 nodes coming online and dropping off again.

In a way, the above two files are the entire application.

The rest is utility code to make the above convenient and concise. That rest might well be 99% of the code, but it’s all structured as loosely-coupled “rigs” (modules), which can be used / overridden / ignored at will.

The way I see it, there can be three sources for such utility code: your own code, plug-ins from others, and a couple of rigs included in the JeeMon core itself. The above two files require just the core, using the built-in rigs (Config, Gui, JeeSketch, Log, Serial, and SysDep).