Implement audiobusio and enhance PIO for it

This adds I2SOut and PDMIn support via PIO.

StateMachines can now:
 * read and read while writing
 * transfer in 1, 2 or 4 byte increments
 * init pins based on expected defaults automatically
 * be stopped and restarted
 * rxfifo can be cleared and rxstalls detected (good for tracking when
   the reading code isn't keeping up)

Fixes #4162

2 files changed, 80 insertions, 0 deletions

diff --git a/tests/circuitpython-manual/audiobusio/i2s_sample_loop.py b/tests/circuitpython-manual/audiobusio/i2s_sample_loop.py
new file mode 100644
index 000000000..c0ee5de31
--- /dev/null
+++ b/tests/circuitpython-manual/audiobusio/i2s_sample_loop.py
@@ -0,0 +1,36 @@
+import audiocore
+import audiobusio
+import board
+import digitalio
+import array
+import time
+import math
+import rp2pio
+import adafruit_pioasm
+
+time.sleep(10)
+
+trigger = digitalio.DigitalInOut(board.D4)
+trigger.switch_to_output(True)
+
+# Generate one period of sine wav.
+length = 8000 // 440
+
+# signed 16 bit
+s16 = array.array("h", [0] * length)
+for i in range(length):
+    s16[i] = int(math.sin(math.pi * 2 * i / length) * (2 ** 15))
+    print(s16[i])
+
+sample = audiocore.RawSample(s16, sample_rate=8000)
+
+dac = audiobusio.I2SOut(bit_clock=board.D10,
+    word_select=board.D11, data=board.D12)
+
+trigger.value = False
+dac.play(sample, loop=True)
+time.sleep(1)
+dac.stop()
+trigger.value = True
+
+print("done")
diff --git a/tests/circuitpython-manual/audiobusio/pdmin_rms.py b/tests/circuitpython-manual/audiobusio/pdmin_rms.py
new file mode 100644
index 000000000..8d1595752
--- /dev/null
+++ b/tests/circuitpython-manual/audiobusio/pdmin_rms.py
@@ -0,0 +1,44 @@
+import audiobusio
+import board
+import digitalio
+import array
+import time
+import math
+
+trigger = digitalio.DigitalInOut(board.D4)
+trigger.switch_to_output(True)
+
+def mean(values):
+    return sum(values) / len(values)
+
+
+def normalized_rms(values):
+    minbuf = int(mean(values))
+    samples_sum = sum(
+        float(sample - minbuf) * (sample - minbuf)
+        for sample in values
+    )
+
+    return math.sqrt(samples_sum / len(values))
+
+# signed 16 bit
+s16 = array.array("H", [0] * 10000)
+
+pdm = audiobusio.PDMIn(clock_pin=board.D11, data_pin=board.D12, sample_rate=24000, bit_depth=16)
+
+print("starting read")
+trigger.value = False
+count = pdm.record(s16, len(s16))
+trigger.value = True
+print("read done")
+print("recorded {} samples".format(count))
+for v in s16[:count]:
+    print(v)
+
+
+magnitude = normalized_rms(s16)
+print("magnitude", magnitude)
+
+print("count", count)
+
+print("done")