Linx Technologies LICAL-DEC-HS001 - Manual (Page 13)

– – – – 20 21
Typical Applications
The HS Series is ideal for registering button presses in secure remote
control applications. An example application circuit of the decoder side is
shown in Figure 12.
In this circuit, the baud has been set for 2,400bps by pulling the SEL_
BAUD line to ground.
SEND_COPY, CREATE_KEY, and LEARN are all connected to buttons
that pull the line high when pressed. Since the lines do not have internal
resistors, 100k
Ω resistors are used to pull the lines to ground when the
buttons are not pressed.
COPY_IN is connected to a port that allows the transfer of the User Data
from another decoder. This port can be a simple wire, an infrared receiver,
or any other circuit that transfers asynchronous serial data.
The KEY_OUT line is connected to a port that allows the transfer of the
key to an encoder or another decoder. This port can be a simple wire, an
infrared diode, or any other device that transfers asynchronous serial data.
The KEY_OUT line can also be connected to a microprocessor or a PC to
record the transmitter identity. Application Note AN-00156 has sample C
code that reads the transmitter ID and displays it on an LCD screen.
An LED indicator is attached to the MODE_IND line to provide visual
feedback that an operation is taking place. This line sources a maximum of
25mA.
2.2k
220
10k
100k
From Receiver
D6
D7
SEL_BAUD
SEND_COPY
GND
GND
COPY_IN
CREATE_KEY
KEY_OUT
MODE_IND D5
D4
D3
D2
VCC
VCC
D1
D0
DATA_IN
LEARN
1
2
3
4
5
6
7
8
9
10 11
12
13
14
15
16
17
18
19
20 LICAL-DEC-HS001
To Key Output Port
From Copy Input Port
100k
100k
Figure 12: HS Series Decoder Application Circuit
The DATA_IN line is connected directly to the data output of the receiver.
Data Lines D0 through D7 can be connected directly to the external
circuitry that is to be activated remotely. In this example, D5 is connected
directly to a piezoelectric buzzer, which causes the buzzer to sound when
the D5 line on the encoder goes high. Line D6 activates a relay through a
transistor buffer when it goes high. A buffer like this may be needed if the
decoder cannot source enough current or voltage to energize the relay coil.
The decoder turns on the transistor, which provides the appropriate drive
levels to the relay.
Typical System Setup
The HS Series offers an unmatched combination of features and security,
yet is easy for system designers and end users to operate. To demonstrate
this, let’s take a brief look at a typical user setup followed by more detailed
design information. The Typical Applications sections of the encoder and
decoder data guides show the circuit schematics on which these examples
are based.
1. Create and exchange a key from a decoder to an encoder.
The high security key is created and exchanged by placing the decoder
in the Create Key Mode. The decoder’s MODE_IND line LED lights to
indicate that the decoder has entered Create Key Mode. The decoder’s
CREATE_KEY button is then pressed ten times to create the key. After
the tenth press, the MODE_IND LED turns off and the decoder sends
the key out of the KEY_OUT line. The MODE_IND LED on the encoder
lights to indicate that the key has been successfully transferred.
2. Establish Control Permissions
The user establishes what buttons on the encoder are recognized by
pressing the decoder's LEARN button. The decoder’s MODE_IND LED
starts flashing and the user presses the encoder buttons that should
be allowed access. Control Permissions are stored when the LEARN
button is pressed again or automatically after 17 seconds.
There are other powerful options such as programming a user PIN or
copying a decoder but these simple steps are all that is required for a
typical setup. It is really that simple for a manufacturer or end user to setup
the product!