add blink example

Author: jepler

examples/pico-examples/blink.py

@@ -0,0 +1,43 @@
+# SPDX-FileCopyrightText: 2021 Jeff Epler, written for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+#
+# Adapted from the example https://github.com/raspberrypi/pico-examples/tree/master/pio/pio_blink
+
+import adafruit_pioasm
+import board
+import array
+import rp2pio
+import time
+
+blink = adafruit_pioasm.assemble(
+    """
+.program blink
+    pull block    ; These two instructions take the blink duration
+    out y, 32     ; and store it in y
+forever:
+    mov x, y
+    set pins, 1   ; Turn LED on
+lp1:
+    jmp x-- lp1   ; Delay for (x + 1) cycles, x is a 32 bit number
+    mov x, y
+    set pins, 0   ; Turn LED off
+lp2:
+    jmp x-- lp2   ; Delay for the same number of cycles again
+    jmp forever   ; Blink forever!
+"""
+)
+
+
+while True:
+    for freq in [5, 8, 30]:
+        with rp2pio.StateMachine(
+            blink,
+            frequency=125_000_000,
+            first_set_pin=board.LED,
+            wait_for_txstall=False,
+        ) as sm:
+            data = array.array("I", [sm.frequency // freq])
+            sm.write(data)
+            time.sleep(3)
+        time.sleep(0.5)