From e538d8a5a6d4c643b1bff41107062511b2e7f65a Mon Sep 17 00:00:00 2001
From: NitiKaur <nitikaur102@gmail.com>
Date: Fri, 5 Nov 2021 15:46:35 +0530
Subject: [PATCH] docs/rp2/quickref.rst: Add section on PIO.

---
 docs/rp2/quickref.rst | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/docs/rp2/quickref.rst b/docs/rp2/quickref.rst
index 63b8928280..4824f390eb 100644
--- a/docs/rp2/quickref.rst
+++ b/docs/rp2/quickref.rst
@@ -92,6 +92,37 @@ Use the :ref:`machine.Pin <machine.Pin>` class::
     p4 = Pin(4, Pin.IN, Pin.PULL_UP) # enable internal pull-up resistor
     p5 = Pin(5, Pin.OUT, value=1) # set pin high on creation
 
+Programmable IO (PIO)
+---------------------
+
+PIO is useful to build low-level IO interfaces from scratch.  See the :mod:`rp2` module
+for detailed explaination of the assembly instructions.
+
+Example using PIO to blink an LED at 1Hz::
+
+    from machine import Pin
+    import rp2
+
+    @rp2.asm_pio(set_init=rp2.PIO.OUT_LOW)
+    def blink_1hz():
+        # Cycles: 1 + 7 + 32 * (30 + 1) = 1000
+        set(pins, 1)
+        set(x, 31)                  [6]
+        label("delay_high")
+        nop()                       [29]
+        jmp(x_dec, "delay_high")
+
+        # Cycles: 1 + 7 + 32 * (30 + 1) = 1000
+        set(pins, 0)
+        set(x, 31)                  [6]
+        label("delay_low")
+        nop()                       [29]
+        jmp(x_dec, "delay_low")
+
+    # Create and start a StateMachine with blink_1hz, outputting on Pin(25)
+    sm = rp2.StateMachine(0, blink_1hz, freq=2000, set_base=Pin(25))
+    sm.active(1)
+
 UART (serial bus)
 -----------------