Linx Technologies LICAL-ENC-HS001 - Manual (Page 11)

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Typical Applications
The HS Series encoder is ideal for registering button presses in secure
remote control applications. An example application circuit is shown in
Figure 11.
In this example, the data lines are connected to buttons, and when any
button is pressed, the SEND line is pulled high and causes the encoder
to transmit. Diodes are used to prevent the voltage on one data line from
affecting another.
The KEY_IN line is attached to a port that allows the key to be transferred
from the decoder during setup. To ensure security, this would normally be
a wire, contact, or short range IR link, although any connection capable of
transferring asynchronous serial data may be utilized.
None of the inputs have pull-up or pull-down resistors internally, so 100k Ω
pull-down resistors are used on the data, SEND, and CREATE_PIN lines.
These resistors are used to pull the lines to ground when the buttons are
not being pressed, which ensures that the pins are always in a known state
and not floating. Without these resistors, the state of the lines cannot be
guaranteed and encoder operation may not be predictable.
An LED is attached to the MODE_IND line to provide visual feedback to
the user that an operation is taking place. This line sources a maximum
of 25mA. An LED can also be connected to the TX_CNTL line to provide
visual indication that the encoder is sending data.
Encrypted data is output on the DATA_OUT line at the baud rate
determined by the SEL_BAUD line. In the circuit above, the baud is set for
4,800bps by pulling it to ground. The DATA_OUT line can be connected
directly to the DATA_IN line of a Linx transmitter or other wireless device.
To Transmitter
100k
100k
220
100k
100k
100k
100k
100k
100k
100k
LICAL-ENC-HS001
D6
D7
SEL_BAUD
SEL_TIMER
GND
GND
KEY_IN
TX_CNTL
DATA_OUT
MODE_IND
D5
D4
D3
D2
VCC
VCC
D1
D0
SEND
CREATE_PIN
1
2
3
4
5
6
7
8
9
10 11
12
13
14
15
16
17
18
19
20
220
To Transmitter PDN
From Key Input Port
100k
Figure 11: HS Series Encoder Application Circuit
The TX_CNTL line may be connected to the PDN line of a Linx transmitter
so that the module will enter a low power state when not in use.
In this example, the data lines are pulled high by simple pushbutton
switches, but many other methods may be employed. Contacts, reed
switches, or microcontrollers are just some examples of other ways to
pull the data lines high. The flexibility of the encoder, combined with the
associative options of the matching decoder, opens a new world of options
for creative product designers.