Computing stuff tied to the physical world

JeeHub Lite

In AVR, Hardware on May 4, 2009 at 00:01

The current JeeHub includes a MMnet1001 Linux module, which is great for running JeeMon. But for an even more basic always-on system, it’s possible to forego the Linux part – here’s the idea:

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The whole thing is powered from USB, which must remain on permanently. There is no need for the attached computer to be on all the time, because incoming data can be saved into the on-board DataFlash memory. Depending on data volume and memory size, it ought to be possible to have a few days of autonomy.

The 433 and 868 MHz OOK receivers make this thing suitable for receiving weather data from off-the-shelf components, as well as responding to KAKU and FS20 remotes (and others like them). And since the RFM12B is so versatile, it can also send out 433 and 868 MHz OOK commands to those systems.

One thing I forgot to add in the above diagram, is a DCF77 receiver – or perhaps using a crystal or RTC. As has been mentioned a few times, the JeeHub needs to have a fairly accurate sense of time to do its main job of collecting real-time readings.

Only a minimal number of signals/ports are needed for the main tasks, there are several pins left to connect a few extra sensors.

The main bottleneck will probably be the amount of code needed to make such a JeeHub Lite perform basic home automation tasks. An Atmega328 might help a bit.

The normal monitoring and reporting work is still done with JeeMon, but now running on the attached PC (which can be Windows, Mac OS X, Linux, whatever). In such a configuration JeeMon must catch-up and extract saved data from the DataFlash in the JeeNode whenever it is launched.