JokamajoInstituut

Since our first prototype implementation based on an Arduino and Fonera 2200 hybrid late last year, we've been busy designing an integrated sensor board for Flukso, our community metering application. The board has an ATmega168v microcontroller (uC) at its core and contains sensor debouncing and signal conditioning circuitry. We can connect one analog and up to three digital pulse sensors to the PCB. Power (3.3V) is drawn from the 4-pin UART header of the main router board.

Flukso sensor board

A 6-pin ICSP header is made available for flashing fuses, flash and EEPROM memory. A Schottky diode protects the sensor board from reverse polarity and current leakage from the 220uF capacitor in case of power loss. In conjunction with the power loss detection circuitry the 220uF elco provides the uC with enough back-up power to save its sensor measurement values to the EEPROM when needed. Last week, we've been soldering the fine-pitched uC and 0603 SMD components onto the PCB. The first sensor board is now connected to to a WAP2102 from Abocom.

Flukso test setup
These very compact router boards have an Atheros AR2317 wireless SoC containing an embedded 32-bit MIPS R4Kc, 4MB Flash and 16MB RAM. We've flashed the device with a customized OpenWRT Kamikaze 8.09 build, hooked it up the sensor board and put it through a first series of tests. We've attached Eagle schematic and layout files. Feel free to use or modify them at will. You can also find a pdf version of the schematic here.

Some additional components that will allow us to mount the contraption into its shiny-white plastic box didn't yet arrive. We'll cover this in a next post. Stay tuned!