The RSSI is indicated in the RX header in the PHY RX Status 1. It is valid only if the PHY RX status valid bit is set.
Depending on some unknown flag that is never changed from the default, the reported RSSI value is calculated as either
- the maximum of the Power 0/1 values (default)
- the minimum of the same
- the average of the same
where both these values are taken as signed 8-bit integer.
If the Power 0 value is 16 or 32, then the power 1 value really is the power 0 value, and the power 1 value is found in the lower 8 bits of PHY RX status 2 (signed again).