Getting Started
2-8
STK512 User Guide
5170C–AVR–10/09
2.3
Teach the Transmitters to the Receiver
In order for the rolling code to work, each transmitter must convey to (teach) the receiver three data ele-
ments: its unique serial number, its secret key, and its sequence counter value. The “learn mode” is
physically activated at the receiver during which time authorized transmitters can transmit their specific
information. This teaching and learning process is accomplished by the following steps.
For security purposes, when the receiver enters the learn mode, all previous data concerning transmit-
ters should be erased. This is discussed in further detail in section 3.2 of the “AVR411: Secure Rolling
Code Algorithm for Wireless Link Application Note” that is furnished on the CDROM. This requirement
has not been implemented in this starter kit in order to allow further investigation into this mode.
Familiarize yourself with the following instructions before beginning the teaching process.
Also, keep your transmitter key fobs readily available. The default timeout to teach a transmitter is 10
seconds before the receiver will exit the learn mode.
1.
Enter learn mode on the receiver by pressing the SW5 button on the STK500. The LED marked
LED5 illuminates, indicating that the receiver is in learn mode.
2.
Within 10 seconds, press Switch 1 on the transmitter key fob you want the receiver to recognize.
Inadvertently pressing any other button or combination of buttons will transmit an ordinary message
that will be ignored by the receiver since the receiver is expecting a longer “teach” message. Once
the receiver receives the “teach” message, the learn-mode LED5 blinks off once, and you have
another 10 seconds to teach the next transmitter. If LED5 does not blink, the message was not
received correctly, perhaps due to interference or an incorrect button combination. Repeat steps 1
and 2 until successful.
Figure 2-7.
Transmitter Key Fob Button Numbering
