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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.

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 10.

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 10: Prototype Board with a Carrier Board