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mcci-catena / arduino-lorawan

User-friendly library for using arduino-lmic with The Things Network and other LoRaWAN® networks
MIT License
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Purpose of NetSaveSessionInfo #165

Closed etix closed 3 years ago

etix commented 3 years ago

NetSaveSessionInfo is supposed to be used to store session info like NwkSKey and AppSKey to avoid new Join requests in conjunction with the other callback GetSavedSessionInfo but the latter is never called. Is there another way to restore the SessionInfo data?

terrillmoore commented 3 years ago

Thanks for your question. (Which version are you commenting on? V0.9.0?)

In any case, it's imperfectly documented, but see this code. TL;DR: you have to implement getAbpProvisioningInfo() for saved sessions on OTAA devices.

https://github.com/mcci-catena/arduino-lorawan/blob/9b664f585941f30fbb69d833d9bbad9f59192ac5/src/lib/arduino_lorawan_begin.cpp#L51-L93

etix commented 3 years ago

Sorry yes, I'm actually upgrading one of my node to 0.9.0 (previously in 0.8.x) in EU868 region.

I'll have a look to getAbpProvisioningInfo() and report back.

Thanks.

etix commented 3 years ago

I've been able to make it work using getAbpProvisioningInfo().

For time travelers who end up on this issue, in addition to the obvious GetOtaaProvisioningInfo() I've also implemented:

For the storage, I'm using the SerialFlash library with the onboard flash chip of my board (Mini Ultra Pro from Rocket Scream).

In NetSaveSessionState() I'm writing the whole SessionState struct into a file. In NetGetSessionState() I'm doing the opposite, reading the file and writing back into the provided SessionState pointer. In NetSaveSessionInfo() I'm writing the whole SessionInfo struct into another file (ignoring pExtraInfo and nExtraInfo). In GetAbpProvisioningInfo() it's a bit more tricky since not everything is in the previously saved SessionInfo. For FCntUp and FCntDown I'm calling NetGetSessionState() from within GetAbpProvisioningInfo() to fetch the counters.

GetSavedSessionInfo() is effectively useless and should probably be removed to avoid confusion.

After a very quick test everything seems to be working (for EU868 at least), no more join request after a cold start.

Thanks again @terrillmoore for the quick answer.