GPIO0 (D3) is the ESP8266 boot strapping pin: an RF receiver holding the
data line low at reset forces the board into flash mode, so a stock
nodemcuv2-rf build never starts after a restart with the receiver wired
to the documented default pin. Default to GPIO4 (D2) instead, which the
docs already recommend as the workaround. Environments that need other
pins (srfb-direct, sonoff-rfr3, rf-wifi-gateway) already override the
value explicitly and are unaffected.
Florian
2459e1c29b