Hi.
I am using MKRWAN with the standard arduino IoT library. My device is quite on the edge regarding signal quality, and I found out that for establishing the connection (joinOTAA) it uses a quite weak data rate ("bandwidth": 125000, "spreading_factor": 7, "coding_rate": "4/5")
As soon as the join is successful, the data packets are sent with a better spreading factor of 12. Then uplink and downlink work without problems.
This also can be seen in practical use. For joining, the antenna has to be outside of the window, but when the device is joined, the connection is stable indoors without problems.
How can I make the join.OTAA be done with a better spreading factor? I tried to modify the Arduino_LoRaConnectionHandler.cpp by adding a call to dataRate(0) into the handleInit. But this has no effect, TTN console still tells me that the join-request packets are sent with SF7
It seems to be a known problem, at least for the mkrwan firmware. But is there really no solution to join the network with the highest range which is possible?
regards,
Arnschi