docs/esp8266/quickref: Add warning block about NeoPixel timing.
@@ -364,6 +364,13 @@ For low-level driving of a NeoPixel::
import esp
esp.neopixel_write(pin, grb_buf, is800khz)
+.. Warning::
+ By default ``NeoPixel`` is configured to control the more popular *800kHz*
+ units. It is possible to use alternative timing to control other (typically
+ 400kHz) devices by passing ``timing=0`` when constructing the
+ ``NeoPixel`` object.
+
+
APA102 driver
-------------
