What kind of accuracy can be expected on the RSSI register count value?
RSSI values from the datasheet:
Typical Receiver Sensitivity of -90 dBm
Typical RSSI value for PWRin > -40 dBm is 28 - 31
Typical RSSI value for PWRin < -95 dBm is 0 -10
Our in-house testing has revealed roughly +/-7.5dBm part variance. RSSI register count vs. input power level is relatively linear over a given power level range.
General note: With a single reading, the RSSI value it is meant to be used for a crude relative signal level measurements between channels and to decide if a signal or interferer is near the noise floor or is plenty strong. Averaging several samples on a channel improves the relative accuracy significantly especially for signals near the noise floor where signal-plus-noise will cause more uncertainty in the RSSI value. The absolute accuracy of the RSSI varies from part to part but is stable over the entire temperature range (+/-1 count) and supply voltage range (+/- 0.5 count). Absolute accuracy would require a careful calibration step in a well controlled final test environment.