AvaLAN Wireless AW900R2-EVAL - Manual (Page 3)

PAGE 3 Technical support (650) 384-0000 www.avalanwireless.com
User’s Manual AW900R2-EVAL
Operational summary
RS-232 is a point-to-point serial data connection that requires just three wires:
Transmit Data, Receive Data and Ground. Because there is no handshake involved,
both ends must be configured for matching data timing and protocol or communica-
tion will not occur. Also, it is possible to lose data if the receiving device cannot
keep up with the sending device. The AW900R2 supports data rates from 9600 Baud
to 115,200 Baud and has a 4 KB data buffer. When properly configured, a pair of
AW900R2 modules behave just like an RS-232 cable but without the length con-
straint and without a physical wire.
Configuring a wireless link with the AW900R2 requires the establishment of six
elements:
• One radio must be configured as the Access Point (AP) and the other one must
be configured as the Subscriber Unit (SU).
• Both radios must share a common Network Name, a 32-bit identifier.
• Both radios must share a common 128-bit encryption key.
• The AP and SU must agree on which radio frequency channel they are using.
This can be manually set or allowed to change automatically.
• The serial port settings: Baud rate, number of data and stop bits and sense of
Parity bit, must match between each radio and the RS-232 device wired to it,
although the radio link may have different settings at each end.
• The AP and SU must share a common set of tuning parameters: Next Byte
Delay, Minimum Packet Size and Maximum Packet Size.
AW900R2 modules are configured through a built-in USB port with a utility program
from AvaLAN. The LED display on the module PC board is also a very useful indicator
of the condition of the wireless connection.
The access point (AP) automatically scans for the best of the 12 available radio
frequency channels, encrypts RS-232 data received, and transmits it wirelessly to
the subscriber unit (SU). The AP is constantly monitoring the radio link and can
automatically change the channel if performance is degraded due to interference.
If two AP units are very close to one another, they may interfere if operating on
adjacent frequency channels. Place them at least 10 feet apart or manually select
non-adjacent channels for their operation. Also, the SU should be placed at least 10
feet from the AP to avoid overloading the radio’s receiver.
At each end of the wireless link, the RS-232 device wired to the AW900R2 must have
its transmit signal connected to the module’s receive and vice versa. Mis-wiring will
not cause damage, but will prevent communication.