docs/esp8266: Consistently replace Pin.high/low methods with .on/off.

docs/esp8266/quickref.rst

@@ -107,8 +107,8 @@ Use the :ref:`machine.Pin <machine.Pin>` class::
     from machine import Pin
 
     p0 = Pin(0, Pin.OUT)    # create output pin on GPIO0
-    p0.high()               # set pin to high
-    p0.low()                # set pin to low
+    p0.on()                 # turn on pin, set to high
+    p0.off()                # turn off pin, set to low
     p0.value(1)             # set pin to high
 
     p2 = Pin(2, Pin.IN)     # create input pin on GPIO2

docs/esp8266/tutorial/pins.rst

@@ -35,8 +35,8 @@ Then set its value using::
 
 Or::
 
-    >>> pin.low()
-    >>> pin.high()
+    >>> pin.off()
+    >>> pin.on()
 
 External interrupts
 -------------------

docs/esp8266/tutorial/repl.rst

@@ -101,11 +101,12 @@ turn it on and off using the following code::
 
     >>> import machine
     >>> pin = machine.Pin(2, machine.Pin.OUT)
-    >>> pin.high()
-    >>> pin.low()
+    >>> pin.on()
+    >>> pin.off()
 
-Note that ``high`` might turn the LED off and ``low`` might turn it on (or vice
-versa), depending on how the LED is wired on your board.
+Note that ``on`` method of a Pin might turn the LED off and ``off`` might
+turn it on (or vice versa), depending on how the LED is wired on your board.
+To resolve this, machine.Signal class is provided.
 
 Line editing
 ~~~~~~~~~~~~