SX1302 RX Downlink via Inverting Chirp Polarization by Changing Specific Registers

Hello LoRa Developer Team!

I setup my own private LoRa network consisting of one SX1302 GW and some end devices, sending basic sensor data. I am currently constructing a simple, passive monitoring system, consisting of multiple SX1302 that sniffs all the uplink and downlink packets of my network. I want to create this diagnostic tool to perform objective tests relating to how a network is actually operating, compared to what my GW and end devices report. I am especially interested in monitoring class B synchronization over extended periods of time and how the network operates under strenuous conditions such as mobile end devices or high interference environments. I need to perform these comprehensive tests to ensure my network maintains stability and resilience.

To program one of my monitor SX1302 to receive downlink packets transmitted by my SX1302 GW, I have been trying to invert the RX chirp polarization. Which registers do I need to change? and why those registers?

The registers below are the ones I believe need to be changed, they have the default values to show they are demodulating non-invert chirp signals. I’ve tried multiple permutations for changing the default values, but I have not been successful yet. I believe the most important register to change is RX_TOP_LORA_SERVICE_FSK_FSK_CFG_3_MODEM_INVERT_IQ, changing default from 0 to 1. The two …CHIRP_INVERT registers are already defaulted to 1 and I believe RX_TOP_LORA_SERVICE_FSK_FSK_CFG_3_RX_INVERT should be set to 1 as well.


{0,SX1302_REG_RX_TOP_BASE_ADDR+135,2,0,1,0,1,1}, // RX_TOP_RX_CFG0_CHIRP_INVERT

{0,SX1302_REG_RX_TOP_BASE_ADDR+127,0,0,1,0,1,1}, // RX_TOP_TXRX_CFG2_CRC_EN


I know there is no access to register documentation, so I would really appreciate any help!

Thank you!!