If you followed the previous posts on this matter, it’s not a surprise that i was thinking of a custom board sooner than later. So here it is – Ardufona: It is a low-power Arduino which runs straight from the battery (pretty much the design of any Bareduino project including ADC-regulation) + Grove-Connectors, 2 for I2C, one Digital, one UART and one for Analog Readings.
It can hook up Adafruits Fona and talk to it and also turn it on and off etc. On the right hand side it has an additional circuit which works as an external watchdog as i figured out that the internal one is not reliable enough to operate the board autonomously in the wild. You can read the considerations behind that guy in this earlier post, but the general principle is easy – if the board turns on the 555 circuit gets also turned on and the capacitor starts to load. If the operation of the board would take too long the 555 would switch and trigger the reset-pin of the Arduino. If everything goes fine the Arduino turns off the 555-watchdog before going to sleep.
I will post the Eagle-Files for this Board and probably also an Order-Link at my favorite PCB-manufacturer soon, but if you want to have a look, find the circuit design below.
Special thanks are going to my friend @chaosblog, who helped me to get this awesome board into my hands.
–> this board is the engine of the awesome “Finding Europe with Lights” project which takes place in cooperation with re:publica, the biggest european web-conference in Berlin on May 5-7. Find out more about the project here: findingeuropewithlights.eu.