Si4010-Keyfob-AES-DEMO

4

Rev 1.1

3.3. Button is Pressed on the Key Fob

If any single button or button combination (except association combination) is pressed on the key fob, then it

transmits a key fob data packet showing the button number in the button field.

3.3.1. Meaning of the Different Fields

Battery, and Rolling counter fields of the packets are extended to 16 bytes length all together and are encoded

by AES-128. Other fields of the packet are not affected by the encryption.

the address.

given button is pressed. If the bit is cleared, the button is released.

represents 0.1 °C. If the temperature function is not implemented in the key fob, this field is set to 0xFFFF.

follows:

the threshold). The LBD limit is configurable in the key fob program.

corresponds to 50 mV. However, 0 represents 1.7 V.

stored in the MTP memory of the Si4010.

Since AES is used by the key fob, the receiver board decrypts the encrypted portion of the packet and discards the

dummy bytes. Then, the receiver board checks the sync counter value against its own copy of the sender key fob's

counter. If the key fob sync counter value minus the copy counter value is more than zero and less than a

configurable window value (default value is 10), the master increments the copy.

Table 3. The MAC Payload Field of the “Key Fob Data” Packet

MAC Payload

NHDR

NWK payload

1byte

1 byte

4bytes

1byte

2 bytes

1 byte

4byte

0x04

AES

Address

Button

TEMP

Battery

Rolling Counter

1bit

1bit

1bit

5bits

Lbd Available

LBD Status

Battery Voltage Available

Battery Voltage[4:0]