Nrf52 isp4520 board proto

I ported and successfully tested in the field my new board with Meshtastic. It works!
The battery life is great and the reception with internal antenna is acceptable (but degrades a lot when out of LOS). Next I plan to test side-by-side with TBeams external antenna.
@geeksville I sent a PR with a bunch of questions, maybe you can take a look when you have a time and let me know what you think?
Another question: while testing the reception, I noticed we only provide SNR in the packet, is there a reason we do not provide RSSI or it is just an oversight?


We could also provide rssi. I added some comments on your cool PR. Alas Iā€™m out of town on vacation until the weekend and can reply more fully then.