Silicon Laboratories Si4010 User Manual page 6

Si4010 Keyfob AES DEMO
Figure 8. Key Fob Association
If the association timeout has not elapsed and an association request packet is received by the radio chip, the
encoded part of the packet will be decrypted using an Association Session Key based on an Association Key and
the sender ID. If decryption was successful, the client rolling counter is synchronized and registered to the clients
list. Figure 9 shows the case when a successful association process completed.
Figure 9. Association Success
When at least one client is associated, the Main screen displays the space used on the list as shown in Figure 10.
Figure 10. Main Screen with Associated Clients
If an AES encoded radio packet is received by the RF Pico board from an associated client (other than an
association request), the payload data is decrypted and displayed on the screen. The associated clients can also
send unencrypted packets, which do not need to be decrypted. The notification screen will be the same in both
cases, except the title, which shows if the packet was AES encrypted or is a Plain text packet.
The encrypted data contains the index from the list and the ID of the sender, the button number pressed on the key
fob, the rolling counter value, the key fob battery voltage, and, finally, the PACap value as shown in Figure 11.
Figure 11. AES Encoded Packet Received
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