add NBConnectionHandler for mkrnb1500

[AlbyIanna]

No description provided.

[aentinger]

@AlbyIanna Your PR looks pretty complete. Unfortunately I've got no board to test it myself, nonetheless I'd like to know if I can/shall merge this in?

[AlbyIanna]

@lxrobotics There is only one thing that worries me: at the following line, I didn't know how to define NETWORK_HARDWARE_ERROR, because for the mkrgsm1400 we used GPRS_PING_ERROR, which I cannot use here because we don't do a ping to test the mkrnb1500 connection
https://github.com/arduino-libraries/Arduino_ConnectionHandler/pull/7/files#diff-5b06e1b92988019060e68def6ba17f7cR119

In fact, these lines don't makes much sense
https://github.com/arduino-libraries/Arduino_ConnectionHandler/pull/7/files#diff-18354ae7f5bbf67659d86e0d3fcabf68R123-R132

[aentinger]

NETWORK_HARDWARE_ERROR need not to be defined, if there is no such error mode available. But from what I see the value of NETWORK_HARDWARE_ERROR could be NB_NetworkStatus_t::ERROR.

You are right, keeping the MKRGSM ping code does not make much sense. The main point at this place in code is to verify that there is actual a connection going on. Can you think of another possibility doing this "alive-"check?

[AlbyIanna]

I have no idea 😕

[Rocketct]

@lxrobotics as you say,the main problem is the fact that the SARA-R410 does not support the URC for the ping, in MKRNB library the access alive check is made checking the registration of the board to the network https://github.com/arduino-libraries/MKRNB/blob/master/src/NB.cpp#L109-L123

[aentinger]

@Rocketct thank you very much for your input. It seems that NB::isAccessAlive could very much be used instead of the ping used for MKR GSM 1400.

[aentinger]

Hey @AlbyIanna 👋
Since this PR is still a work-in-progress may I ask you to restructure NBConnectionHandler::update in a similiar way as I've restructed WiFiConnectionHandler::update? By extracting the state specific code in private member functions state transitions and errors can be seen much easier.
Thank you, Alex