esp32/quickref.rst: Add DAC example.

Signed-off-by: IhorNehrutsa <Ihor.Nehrutsa@gmail.com>

docs/esp32/quickref.rst

@@ -141,7 +141,7 @@ These are working configurations for LAN interfaces of popular boards::
     # Olimex ESP32-GATEWAY: power controlled by Pin(5)
     # Olimex ESP32 PoE and ESP32-PoE ISO: power controlled by Pin(12)
 
-    lan = network.LAN(mdc=machine.Pin(23), mdio=machine.Pin(18), power=machine.Pin(5), 
+    lan = network.LAN(mdc=machine.Pin(23), mdio=machine.Pin(18), power=machine.Pin(5),
                       phy_type=network.PHY_LAN8720, phy_addr=0,
                       ref_clk=machine.Pin(17), ref_clk_mode=machine.Pin.OUT)
 
@@ -330,6 +330,19 @@ possible at the same frequency.
 
 See more examples in the :ref:`esp32_pwm` tutorial.
 
+DAC (digital to analog conversion)
+----------------------------------
+
+On the ESP32, DAC functionality is available on pins 25, 26.
+On the ESP32S2, DAC functionality is available on pins 17, 18.
+
+Use the DAC::
+
+    from machine import DAC, Pin
+
+    dac = DAC(Pin(25))  # create an DAC object acting on a pin
+    dac.write(128)      # set a raw analog value in the range 0-255, 50% now
+
 ADC (analog to digital conversion)
 ----------------------------------