Specifications

44
Fig. 4.3: Picture of the Maxstream XBee-Pro radio module.
module used 30mA active, 55mA RX, and 215mA TX.
The crucial requirement that the radio’s network function (i.e., coordinator, router,
or endpont) be dynamically allocated led designers to select the Maxstream XBee-Pro [44]
(see fig. 4.3). Its power consumption makes is a non-ideal solution. However, Maxstream
has certified the DataManager and its development and given intellectual rights to allow
this device to reconfigure their radio. This level of cooperation and customer service also
encouraged the designers with this selection. However, as better ZigBee products become
available, the device will migrate to support a more ideal solution. T he XBee-Pro uses a
standard UART to communicate to its host. Therefore, the second UART on the MCU was
dedicated to the radio.
4.1.8 External SPI Flash
The common sizes for inexpensive SPI flash are 2Mbit (256KB), 4Mbit (512KB), and
8Mbit (1MB). Two different chips were found that satisfied the operational and sleep mode
functional requirements. Both have similar interfaces and are 8Mb in size. O ne of these
devices is Atmel’s AT45DB081X [45]. It claims a 2-10µA sleep current and 4mA read and
15mA write curr ent. The other device is Spansion’s S25FL008A [46]. This part has a .2-5µA
sleep current and a 1.5mA read and 7mA write current. Both chips cost about a $1.20. The
Spansion part was selected over the Atmel part. However, th ere were s ome reservations