http://github.com/JChristensen/aaXBee_HW
ReadMe file
Jack Christensen Mar 2015
A low-power, Arduino-compatible XBee sensor node that runs on two AA cells. It should run for over a year on a pair of AA alkaline cells (this could be reduced if sensors that require relatively large amounts of power or on-time are used). For an example sketch, see the aaXBee sketch in my GroveStreams library. The AA XBee Node will send data to an Arduino running the gsGateway sketch, which forwards it to the GroveStreams web site. (Also see my blog post, A GroveStreams Wireless Sensor Network.)
The AA XBee Node includes an accurate real-time clock (DS3231, ±2ppm from 0°C to +40°C) for precise timing of data transmissions and an accurate on-board I2C temperature sensor (MCP9808, ±0.25°C typical). A prototyping area is provided for connecting additional sensors. Twelve microcontroller GPIO pins are available to interface with sensors, including the I2C and SPI buses and analog inputs. A pushbutton switch and an LED are available for application use.
The Double-A XBee Sensor Node is a flexible design with three major configuration options based on the voltage and power required by application-specific sensors. One or two boost regulators are used to supply 3.3V to the XBee and either 3.3V or 5V to the MCU and sensors.These configurations are summarized on page 2 of the aaXBee_BOM.pdf file.
Various components are also optional depending on requirements. See page 3 of the aaXBee_BOM.pdf file for comments on optional components.
To conserve power, the AA XBee Node disables the boost regulator(s) and sleeps using the battery voltage directly (sleep current is < 5µA). With the regulator(s) disabled, the MCU's clock speed is reduced to avoid overclocking. Because of this, the board should be programmed with an in-circuit serial programmer (ICSP, e.g. AVRISP mkII, USBtinyISP, USBasp, etc.) as opposed to a bootloader. As part of this approach, specific fuse settings are required, so a custom entry in the Arduino boards.txt file is also recommended as follows:
##############################################################
aaDL.name=Double-A Datalogger/Double-A XBee Node
aaDL.upload.protocol=arduino
aaDL.upload.maximum_size=32768
aaDL.bootloader.low_fuses=0x7f
aaDL.bootloader.high_fuses=0xde
aaDL.bootloader.extended_fuses=0x06
aaDL.build.mcu=atmega328p
aaDL.build.f_cpu=8000000L
aaDL.build.core=arduino
aaDL.build.variant=standard
##############################################################
"Double-A XBee Sensor Node" by Jack Christensen is licensed under CC BY-SA 4.0.