Tips for inclusion in README

[ceekdee]

Tips:

• there are three levels of debugging for the embassy lora_xxx.rs examples:
  • take DEFMT_LOG=aaaa cargo run --bin lora_lorawan --release as an example
  • aaaa=info provides whatever debugging is set up outside lora-phy
  • aaaa=debug provides modest tx/rx packet handling information for lora-phy, including modulation and power
  • aaaa=trace provides all the write/read interactions through SPI to the LoRa board. I would not suggest pasting all that to a GitHub issue or this room, since it includes all the data that is written and read, which you may wish to keep private.
• if running an embassy lora_lorawan.rs example, you need to first edit it to set up a few things to match your end device, region, and LoRaWAN service. The lora_p2p_xxx.rs examples need to be edited to set a valid frequency for your region.
• for The Things Network (TTN), the deveui needs to be specified as lsb, not msb, for lora_lorawan.rs. The TTN console displays both for you to copy. The appkey doesn't have this issue (use as-is). I am not sure how the appeui should be set, since I have only used all zeros for that.
• if you are using an 8 channel TTN gateway for US915, it will not work reliably with rust-lorawan/embassy/lora_phy. The problem is that this gateway only supports a sub-band of the possible frequencies while rust-lorawan currently uses the complete range of frequencies. There is work being done in rust-lorawan to support sub-bands, and perhaps there is another way around this in rust-lorawan setup I haven't discovered yet short of patching three lines of code in rust-lorawan.
• document the custom LoRa board implementation feature.