Is it possible to use a SW defined radio tuned to 868 MHz to detect LoRa Node radio transmissions?

[arjanvanb (Arjan)]

@jerrymek

I’m deliberating wether to send the data in JSON format and then compact with CBOR

I feel CBOR is really unpredicatable, hence a bad choice for LoRaWAN:

@arjanvanb

Even when using {"t": 23}, you’d still get 4 bytes for A1 61 74 17. A fixed position encoding, with an unrealistic temperature accuracy of 2 decimals, would allow for -327.68 thru 327.67 in just 2 bytes.

Adding a decimal in CBOR, {"t": 23.5} yields 6 bytes in A1 61 74 F9 4D E0. But other values might go crazy, like {"t": 23.4} yields the whopping A1 61 74 FB 40 37 66 66 66 66 66 66. Play around with http://cbor.me/ before considering using CBOR.

@jerrymek

or if I should just send bytes with data in binary format and then a checksum in the end

A checksum (the MIC) is already included in each LoRaWAN message. If that fails, your application won’t even see the uplink. (Even more: TTN wouldn’t even be able to tell it’s your uplink.)