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9

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.

Using the Remote Control Demo Board

Snap a Carrier Board onto the socket on each Remote Control Demo

Board as shown in Figure 9.

Insert 4 AAA batteries into the holders on the back of each board, connect

antennas and turn on power.

The modules come paired out of the box, but to Pair additional modules,

press the PAIR button on both boards. The MODE_IND LEDs flash to

indicate that the modules are searching for each other and exchanging

addresses. The MODE_IND has a quick flash while searching (100ms on,

900ms off) and a longer flash once Pairing is complete (400ms on, 100ms

off). This process only takes a few seconds. The pairing process takes the

status line input / output directions into account. If these are changed then

the modules should be paired again.

Once complete, pressing a button on one board (the Initiating Unit or IU)

causes an LED to light up on the other board (the Responding Unit or RU).

The RU sends an acknowledgement message to the IU. If the message is

valid, the IU turns on the CONFIRM LED.

Figure 9: Remote Control Demo Board with a Carrier Board

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.

times and hold it down on the fifth press. The MODE_IND LED flashes

when it has reset. Alternatively press and hold the RESTORE button on

the back of the board for 5 seconds. When the LED turns off, release the

button and the LED flashes twice to indicate a successful restore.