The two most common RF radios that are available from Digi are the 802.15.4 and ZB. The 802.15.4 and ZB modules are quite similar, but selection of a module should be based upon application specific needs.
All XBee radios have the same footprint and for the most part-are pin for pin compatible (with a few differences in the placement of ADC/IO lines), but are NOT interoperable. The 802.15.4 and ZB (Zigbee) (S2 and S2C) modules offer different application profiles, which are unique to each radio family. They can however, use the same RS232 or USB interface boards.
Product comparison specification Quick Facts for the non-pro variant of the three products:
| ||XBee 802.15.4||XBee ZB S2||XBee ZB S2C|
|Indoor/Urban range||up to 100 ft. (30m)||up to 133 ft. (40m)||up to 200 ft (60 m)|
|Outdoor RF line-of-sight range||up to 300 ft. (100m)||up to 400 ft. (120m)||up to 4000 ft (1200m)|
|Transmit Power Output||1 mW (0dbm)||2 mW (+3dbm)||6.3mW (+8dBm) Boost mode|
3.1mW (+ddBm) Normal mode
|RF Data Rate||250 Kbps||250 Kbps||250 Kbps|
|Receiver Sensitivity||-92dBm (1% PER)||-98dBm (1% PER)||-102dBm (1% PER) Boost mode|
-100dBm (1% PER) Normal Mode
|Supply Voltage||2.8 - 3.4 V||2.8 - 3.6 V||2.1 - 3.6V|
|Transmit Current (typical)||45 mA (@ 3.3 V)||40 mA (@ 3.3 V)||45 mA (+8dBm) Boost Mode|
33 mA (+5dBm) Normal Mode
|Idle/Receive Current (typical)||50 mA (@ 3.3 V)||40 mA (@ 3.3 V)||31 mA (+8dBm) Boost Mode|
28 mA (+5dBm) Normal Mode
|Power-down Current||10 uA||1 uA||<1uA|
|Frequency||ISM 2.4 GHz||ISM 2.4 GHz||ISM 2.4 GHz|
|Dimensions||0.960" x 1.087"|| ||Through-Hole: 0.960" x 1.087"|
SMT: 0.866" x 1.33" x 0.120"
|Operating Temperature||-40 to 85 C||-40 to 85 C||-40 to 85 C|
|Antenna Options||PCB, Integrated Whip, U.FL, RPSMA||PCB, Integrated Whip, U.FL, RPSMA||Through-Hole: PCB, Integrated Whip, U.FL, RPSMA|
SMT: RF pad, PCB, or U.FL
|Network Topologies||Point to point, Star, Mesh (with DigiMesh firmware)||Point to point, Star, Mesh||Point to point, Star, Mesh|
|Number of Channels||16 Direct Sequence Channels||16 Direct Sequence Channels||16 Direct Sequence Channels|
|Filtration Options||PAN ID, Channel & Source/Destination||PAN ID, Channel & Source/Destination||PAN ID, Channel & Source/Destination|
Since hardware specifications are similar, the differences between XBee 802.15.4 and ZB are more evident in the firmware features. Listed below are some of the more defining differences in the firmware:
- 802.15.4: XBee Series 1 comes standard with 802.15.4 firmware for point-point or star topology. This mature firmware offers ADC (analog-to-digital conversion) inputs, and digital and analog I/O line passing. The 802.15.4 XBee is significantly faster than ZigBee; RF latency can generally be calculated in 802.15.4. Throughput is also much higher, a practical maximum throughput is around 80kbps.
- ZigBee: XBee ZB does not offer any 802.15.4-only firmware; it is always running the ZigBee mesh firmware. The ZigBee XBee excels in very low-power scenarios, when configured as an End Device, this module has the lowest current draw of any Digi RF product. However, the infrastructure of a ZigBee network is more complex and requires more configuration to fully implement. The main benefit of a ZigBee XBee is third-party Zigbee device support and deep integration with the Device Cloud and Digi gateway products.
- One unique benefit of the 802.15.4 XBee is that it can have the DigiMesh firmware installed. DigiMesh is Digi proprietary mesh network protocol and is direclty comparable to ZigBee. This allows a small network to be implemented as a Star topology, then later converted into a full mesh network without replacing hardware. A whitepaper comparing DigiMesh and ZigBee can be found here: http://www.digi.com/pdf/wp_zigbeevsdigimesh.pdf.
A study of the product manuals to compare the XBee 802.15.4, ZB (S2) and the ZB (S2C) radios more completely is left to the user. However, Digi Applications Engineers are available to discuss these differences in greater detail, and can be reached at 1-801-765-9885.