Q: Does RSSIREFERENCE register has any effect on the receiver? Could it affect receiver performance? Is it added to hardware RSSI that is measured by the chip prior to being read via the RSSI FIFO command and/or prior to being compared against RSSIABSTHR? We wonder because the axRadioLab suggests putting 0x05 in RSSIABSTHR. Is this the loss in the DVK2 boards?
A: The RSSIREFERENCE value affects the RSSI register reading, the value you get from the RSSI FIFO command and the value compared against RSSIABSTHR. The 0x05 is not the loss of the DVK2 board.
Please note: The gain of the digital channel filter stage changes depending on the DECIMATION setting. AX-RadioLAB sets the RSSIREFERENCE to correct for this. In addition, AX-RadioLAB code sets the RSSIREFERENCE 64 dB (called RSSIOFFSET) higher than the correct value and then subtracts 64 dB when reading out the RSSI value. (And also corrects RSSIABSTHR by 64). This is to prevent wrap around at -128 dBm, since the RSSI register is only 8 bit. For more details on the registers check out the programmers manual.