(sysname='LoPy', nodename='LoPy', release='1.7.9.b3', version='v1.8.6-747-gc4ec6110 on 2017-08-09', machine='LoPy with ESP32', lorawan='1.0.0')

I tried to Add the FSK Channel from LoRaWAN 868 MHz (DR = 7) with the following command:

lora.add_channel(8, frequency=868800000, dr_min=7, dr_max=7)

An then i get the Error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid argument(s) value

I think the Error is in:

esp32/mods/modlora.c :
lora_validate_data_rate()

It aborts, when the datarate is greater than DR_6 and that is wrong, because in 868 MHz band it can go to DR_7.