Jon Rob 1678f41744 esp32/esp32_rmt: Extend RMT to support carrier feature.
The ESP32 RMT peripheral has hardware support for a carrier frequency, and
this commit exposes it to Python with the keyword arguments carrier_freq
and carrier_duty_percent in the constructor.  Example usage:

    r = esp32.RMT(0, pin=Pin(2), clock_div=80, carrier_freq=38000, carrier_duty_percent=50)
2020-06-17 00:03:33 +10:00
..