Adapt first example from the Micropython book

examples/getting-started/led_brightness.py

@@ -0,0 +1,40 @@
+# SPDX-FileCopyrightText: 2021 Jeff Epler, written for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+#
+# Adapted from the an example in Appendix C of file:///tmp/mozilla_jepler0/RPi_PiPico_Digital_v10.pdf
+
+import adafruit_pioasm
+import board
+import rp2pio
+import time
+
+led_quarter_brightness = adafruit_pioasm.assemble("""
+    set pins, 0 [2]
+    set pins, 1
+""")
+
+led_half_brightness = adafruit_pioasm.assemble("""
+    set pins, 0
+    set pins, 1
+""")
+
+led_full_brightness = adafruit_pioasm.assemble("""
+    set pins, 1
+""")
+
+while True:
+    sm = rp2pio.StateMachine(led_quarter_brightness,
+        frequency=10000, first_set_pin=board.LED)
+    time.sleep(1)
+    sm.deinit()
+
+    sm = rp2pio.StateMachine(led_half_brightness,
+        frequency=10000, first_set_pin=board.LED)
+    time.sleep(1)
+    sm.deinit()
+
+    sm = rp2pio.StateMachine(led_full_brightness,
+        frequency=10000, first_set_pin=board.LED)
+    time.sleep(1)
+    sm.deinit()