Add an example using the RP2350 "mov ,txfifo[]" feature

examples/pioasm_rp2350_fifo.py

@@ -0,0 +1,84 @@
+# SPDX-FileCopyrightText: 2024 Jeff Epler, written for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
+"""A PIO demo that uses the FIFO in random access mode
+
+Random access mode is a new feature of the PIO peripheral of the RP2350.
+This demo is not compatible with the original RP2040 or Raspberry Pi
+Pico.
+
+Wiring:
+ * LED with current limiting resistor on GP25 (Pico 2 standard location)
+
+The LED will blink in several patterns depending on the values loaded in the 'rxfifo' registers
+"""
+
+import array
+import time
+import board
+import rp2pio
+import adafruit_pioasm
+
+program = adafruit_pioasm.Program(
+    """
+    .pio_version 1
+    .set 1
+    .fifo txget
+
+    ; LED on time taken from rxfifo[0]
+    mov osr, rxfifo[0]
+    mov x, osr
+
+    set pins, 1
+xloop1:
+    jmp x--, xloop1
+
+    ; LED off time taken from rxfifo[1]
+    mov osr, rxfifo[1]
+    mov x, osr
+
+    set pins, 0
+xloop2:
+    jmp x--, xloop2
+    """
+)
+
+
+def assign_uint32s(ar, off, *args):
+    """Assign multiple 32-bit registers within an AddressRange"""
+    vv = b"".join(v.to_bytes(4, "little") for v in args)
+    ar[off : off + 4 * len(args)] = vv
+
+
+print(program.pio_kwargs)
+sm = rp2pio.StateMachine(
+    program.assembled,
+    first_set_pin=board.GP25,
+    frequency=10_000_000,
+    **program.pio_kwargs,
+)
+fifo = sm.rxfifo
+
+# Set non-zero register entries & re-start the state machine at its offset.
+# this is needed because the default register value could represent a very long delay
+fifo[0:4] = b"\1\0\0\0"
+fifo[4:8] = b"\1\0\0\0"
+sm.run(array.array("H", [sm.offset]))
+
+while True:
+    # equal blinks
+    assign_uint32s(fifo, 0, 2000000, 2000000)
+    time.sleep(1)
+
+    # small on time
+    assign_uint32s(fifo, 0, 1000000, 3000000)
+    time.sleep(1)
+
+    # small off time
+    assign_uint32s(fifo, 0, 3000000, 1000000)
+    time.sleep(1)
+
+    # slower blinks
+    assign_uint32s(fifo, 0, 3000000, 3000000)
+    time.sleep(1)