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Range Testing
Several complex mathematical models exist for determining path loss in
many environments. These models vary as the transmitter and receiver are
moved from indoor operation to outdoor operation. Although these models
can provide an estimation of range performance in the field, the most
reliable method is to simply perform range tests using the modules in the
intended operational environment.
Range testing can be performed with the Remote Control Demo Boards.
To prepare the board for range testing, simply turn it on by switching the
power switch to the ON position. Pressing a status line button on one
board (the IU) activates an LED on the other board (the RU). The RU then
sends an acknowledgement back to the IU, which turns on the CONFIRM
LED. This indicates good bi-directional RF communications and lets the
user set one board down and walk with the other board.
As the maximum range of the link in the test area is approached, it is not
uncommon for the signal to cut in and out as the radio moves. This is
normal and can result from other interfering sources or fluctuating signal
levels due to multipath effects. This results in cancellation of the transmitted
signal as direct and reflected signals arrive at the receiver at differing times
and phases. The areas in which this occurs are commonly called “nulls”
and simply walking a little farther usually restores the signal. If the signal is
not restored, then the maximum range of the link has been reached.
To achieve maximum range, keep objects such as your hand away from
the antenna and ensure that the antenna on the transmitter has a clear and
unobstructed line-of-sight path to the receiver board. Range performance
is determined by many interdependent factors. If the range you are able to
achieve is significantly less than specified by Linx for the products you are
testing, then there is likely a problem with either the board or the ambient
RF environment in which the board is operating. First, check the battery,
switch positions, and antenna connection. Next, measure the receiver’s
RSSI voltage with the transmitter turned off to determine if ambient
interference is present. High RSSI readings while the transmitter off indicate
there is interference. If this fails to resolve the issue, please contact Linx
technical support.
Note: The Remote Control Demo boards are designed for hardware
configuration. If the modules are changed through software configuration
then the boards may not operate as expected. A restore to default
configuration can be used to reset the modules.
Using the Prototype Board
Snap a Carrier Board onto the socket on the Prototype Board as shown in
Figure 12.
Place the power switch into the “USB” position then connect a micro USB
cable into the connector at the top of the board. Plug the other end into a
PC or any USB charger. The board is powered by the USB bus. This board
features a prototyping area to facilitate the addition of application-specific
circuitry. The prototyping area contains a large area of plated through-holes
so that external circuitry can be placed on the board. The holes are set at
0.100” on center with a 0.040” diameter, accommodating most industry-
standard SIP and DIP packages.
At the top of the prototyping area is a row connected to the 3.3V power
supply and at the bottom is a row connected to ground. External circuitry
can be interfaced to the transceiver through the breakout headers. The
numbers next to the headers correspond to the pin numbers on the Carrier
Board. Figure 4 shows the pin assignments for the Carrier Board.
The OVERLOAD LED indicates that that too much current is being pulled
from the USB bus. This is used to prevent damage to the parts or the bus.
The overload condition is reset once the excess current draw is removed.
Figure 12: Prototype Board with a Carrier Board
