This is a random idea I had a few months ago. I wanted a small cheap wireless module that could be setup as a mesh network of sensors. This of course could be describing XBees, but I wanted something of my own. My implementation uses the RFM12B wireless module which costs around 6$ in single quantities. An ATtiny84 microcontroller on back will do all of the processing over SPI.
My prototype board is partially assembled. I am missing some 0603 resistors needed to connect the SPI lines on the wireless module to the MCU. I also reminded myself how painful it is to try and solder SMT parts without the proper equipment. I am a fan of solder paste and a cheap reflow oven. If those aren’t available a regular soldering iron works as long as there is plenty of flux. With plenty of flux soldering 0402 isn’t even a problem! Unfortunately my flux was nowhere to be found. I’m saving my second prototype board for when I have some solder paste and can compare the two boards.
In terms of the idea behind the board, I plan on writing my own software to communicate between nodes on a wireless mesh network. There are two outputs/inputs on each node. This means I could easily attach 1-wire or analog sensors to the board, toggle a switch, send IR commands, etc.
The next revision of the board will be smaller, hopefully matching the dimensions of the wireless module. It will also include a coin cell battery holder.
More to come when I get the parts I need and I start on the software.