It looks impressive, but, um, what is it?
We have a network of gadgets throughout the house. They're mainly there to flash strobes and attract barakta's attention to things like the doorbell or phone ringing, but also include sensors to control the heating, and some other random stuff. I cobbled it together on a shoestring budget about ten years ago based on a flaky I
2C bus and low-end PICs, with software running on a server to do all the clever bits. It's been overdue for replacement for ages now, but I keep riding my bike instead.
I decided that the new version needed to be as simple and reliable as possible. IP/Ethernet rather than hard to debug proprietary comms. Wireless as an option. Alterting functions separate from sensing functions at a software level. That sort of thing. Expandable and upgradable, where possible, without having to dig out tatty circuit diagrams and boggling at spaghetti code more than absolutely necessary. That sort of thing.
The Pi makes the bulk of that utterly trivial. It speaks IPv6 over Ethernet (or Wifi with a dongle). The GPIO port allows easy interfacing with the rest. That board contains: RS232 port (for controlling our LED matrix signs, which means we can ditch a load of serial cabling that's running back to the server); Dallas 1-wire interface, with temperature and humidity sensors on-board, and RJ45 connector with a standard pinout for connecting more; SPI buffering for RGB addressable LEDs (which are a cheap and flexible way to do an attention-getty front panel that's viewable from across a room); cheap and nasty audio amp, with a mute control so it doesn't make annoying buzzing noises when idle (the analogue audio on the RPi is shite, but adequate for notification type stuff); switching power regulator to power the Pi and I/O stuff.
Power over Ethernet
[1] is yet to be added, as is the driver for the zenon strobe, PIR and light level sensors and a bit of uncommitted buffered GPIO, because there's always the unforseen. I'm also toying with the idea of local battery backup (the PoE injector will be on a UPS, but that's no good if it's running wirelessly or off the back of a cheapo switch, powered by a local wall-wart).
OWFS handles the 1-wire sensors out of the box. I've written some test code for the LEDs. Networking, serial, audio and so on are all standard Linux stuff. Then it's basically a matter of RRDtool and some code and config files to tie everything together. I suspect I'll have to do some proper work to make a SIP client phone ringer that can register with our Asterisk server, but the rest should be pretty straightforward. The USB and HDMI ports should be accessible, so it can have a screen and keyboard connected for use as an IRC/SSH/not much else terminal - this will allow us to retire the WYSE serial terminal with the b0rked proprietary keyboard in the kitchen, and the Pentium II laptop in the bedroom.
Then I'll have to work out how to use Eagle properly, and think long and hard about physical construction. I appear to be capable of soldering a TSSOP without cocking it up, but I'm rubbish at cutting holes in panels.
ETA: Incidentally, I can recommend
these prototyping boards.
ETA2: Got the PoE working.
[1] Which is, unfortunately, going to have to be a bit of a bodge, because the Raspberry Pi's Ethernet jack doesn't expose the wires downstream of the magnetics.
