May
2004, Issue 166
Radio
Roundup
RADIOMETRIX
SpacePort
Atmel
has been well represented in the embedded radio controller
role thus far. The Radiometrix SpacePort data radio
prevents a shutout and incorporates a PIC16F876 to invoke
its RF features. From what I could glean from the SpacePort
documentation, the PIC is the radio packet modem (RPM).
A fast radio packet controller (FRPC) works in conjunction
with the RPM and resides under the shield with the SpacePort’s
RF circuitry. It’s just a guess, but looking at the
SpacePort documentation, the FRPC is most likely a PIC16F84A
running at full speed (20 MHz).
My
SpacePort module (SPM) evaluation kit came with a pair
of SPM2-433-28 433-MHz radio modules and a pair of matching
evaluation boards. Options can be exercised to get the
SpacePort modules configured for the 869- and 900-MHz
bands. There are a bunch of configuration options that
can be dialed into the SpacePort, and the configuration
parameters are set using a simple terminal program like
HyperTerminal or Tera Term Pro. Photo 5 is a shot of
what my SPM spit out when I jumpered it into Setup/Configuration
mode.
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(Click
here to enlarge)
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Photo
5—The SpacePort SPM2-433-28 is an international
kind of data radio. Note the FCC airspeed setting.
If you’re wondering, the radar setting is for range
testing. |
As
you might ascertain from the SPM configuration entries,
the SpacePort is packet-oriented and designed to work
well in addressable wireless networks. To that end,
the SpacePort performs error checking, packet acknowledgement,
and retransmission functions to help guarantee the integrity
of data flowing on the wireless links. The SpacePort’s
maximum acknowledged throughput is 28 kbps. Unacknowledged
throughput is rated at a maximum of 55 kbps.
The
SpacePort only requires a simple three-wire interface
to a controlling host: transmit data (TXD), receive
data (RXD), and clear-to-send (CTS). However, particular
attention has been directed toward providing plenty
of visual feedback relative to the condition of the
wireless link and the data flowing across it. Figure
2 is a pretty good representation of how the SpacePort
module can be deployed; it closely follows the way the
SPM is implemented on the SpacePort evaluation board.
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(Click
here to enlarge)
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Figure
2—To make implementing the SpacePort as simple as
implementing the XTR-903-A4, you can use any microcontroller,
eliminate the RS-232 driver, pull your 5 VDC from
an existing power source in your project, and chuck
the LEDs. |
