Linx Technologies EVAL-xxx-LR - Manual (Page 5)

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Theory of Operation
Transmitter Evaluation Board
The transmitter board is powered by an on-board 3V CR2032 lithium
battery. It has eight SPST pushbutton switches, the state of which is
encoded into a data stream using a Linx MS Series encoder. If a switch
is closed, the transmitter is enabled while the encoder captures the
pushbutton states for encoding and transmission. The encoder powers
down the transmitter when the button is released. Buttons S0 (D0) and
S1 (D1) are used to activate the LED and buzzer on the receiver board.
All of the data lines have been wired out to the header to the right of
the prototyping area and can be accessed for use with other switches,
contacts or microcontrollers.
Receiver Evaluation Board
The receiver board is powered by two AAA batteries. The LR Series
receiver exhibits a sensitivity of greater than –112dBm, so under optimum
line-of-sight conditions, the transmitter / receiver link can operate over
distances of up to 3,000 feet (1,000m). The data recovered by the LR
Series receiver is decoded by a MS Series decoder, and the data lines
are updated to match the state of the data lines (or pushbuttons) on the
transmitter board. To demonstrate this, one data line is used to drive an
LED while another is used to activate a buzzer. This board also has a
prototyping area with all of the receiver and decoder lines brought out to a
header.
Using the Kit
Using the kit is straightforward. Simply attach the antennas, turn on the
power and press buttons on the transmitter board. When S0 is pressed,
the buzzer sounds; when S1 is pressed, the LED turns on. When any
button (S0–S7) is pressed on the transmitter board, the corresponding
decoder output (D0–D7) is active high (V
CC
) on the prototyping header.
Development Using the Prototyping Area
In addition to their evaluation functions, the boards may also be used for
product development. They feature a prototyping area to facilitate the
addition of application-specific circuitry. This area has a connection to
V
CC
at the top and ground at the bottom that can be used to power any
circuitry that is added.
The holes are plated and set at 0.1" on center with a 0.04" diameter,
making it easy to add most industry-standard SIP and DIP packages to the
board.
On the transmitter board, the data lines from the encoder and the PDN line
from the transmitter have been wired out to a row of plated holes on the
right side of the prototyping area. On the receiver board, the data lines from
the decoder plus the RSSI, PDN, and DATA lines from the receiver have
been wired out. This allows for easy access to connect external circuitry to
the modules, the encoder, and the decoder. Data line D0 is connected to
the buzzer and D1 is connected to the LED.
Note: The CR2032-style battery on the transmitter board has very low
current capacity with, only about 3mA available for external circuitry. If
added circuitry requires a higher current, the battery must be removed
and the board powered from an external source.