SWRS045F January 2006 – November 2018 CC1021
PRODUCTION DATA.
The CC1021 device has a built-in feature called AFC (Automatic Frequency Control) that can be used to compensate for frequency drift.
The average frequency offset of the received signal (from the nominal IF frequency) can be read in the AFC register. The signed (2-complement) 8-bit value AFC[7:0] can be used to compensate for frequency offset between transmitter and receiver.
The frequency offset is given by Equation 22.
The receiver can be calibrated against the transmitter by changing the operating frequency according to the measured offset. The new frequency must be calculated and written to the FREQ register by the microcontroller. The AFC can be used for an FSK/GFSK signal, but not for OOK.
The AFC feature reduces the crystal accuracy requirement.