tests/extmod: Add test for machine.I2S data rate.

Signed-off-by: Damien George <damien@micropython.org>

tests/extmod/machine_i2s_rate.py

@@ -0,0 +1,80 @@
+# Test machine.I2S data transfer rate, for both TX and RX.
+
+try:
+    from machine import Pin, I2S
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
+import time, sys
+
+# Configure pins based on the board.
+if "pyboard" in sys.platform:
+    i2s_id = 2
+    sck_pin = Pin("Y6")
+    ws_pin = Pin("Y5")
+    sd_pin = Pin("Y8")
+elif "rp2" in sys.platform:
+    i2s_id = 1
+    sck_pin = Pin(0)
+    ws_pin = Pin(1)
+    sd_pin = Pin(2)
+
+TEST_BYTES = b"01234567"
+RATE = 11025  # frames/sec
+
+
+def test(mode, bits_per_sample, frame_format):
+    i2s = I2S(
+        i2s_id,
+        sck=sck_pin,
+        ws=ws_pin,
+        sd=sd_pin,
+        mode=mode,
+        bits=bits_per_sample,
+        format=frame_format,
+        rate=RATE,
+        ibuf=200,
+    )
+
+    if frame_format == I2S.MONO:
+        channels = 1
+    else:
+        channels = 2
+    bits_per_frame = bits_per_sample * channels
+    buf_len_250ms = bits_per_frame // 8 * RATE // 4
+
+    # Create test data and preload I2S buffers.
+    if mode == I2S.TX:
+        mode_str = "TX"
+        data = TEST_BYTES * (buf_len_250ms // len(TEST_BYTES))
+        i2s.write(data)
+    else:
+        mode_str = "RX"
+        data = bytearray(len(TEST_BYTES) * (buf_len_250ms // len(TEST_BYTES)))
+        i2s.readinto(data)
+
+    # Time how long it takes to read/write 2 lots of data.
+    t0 = time.ticks_ms()
+    for i in range(2):
+        if mode == I2S.TX:
+            i2s.write(data)
+        else:
+            i2s.readinto(data)
+    t1 = time.ticks_ms()
+    dt = time.ticks_diff(t1, t0)
+
+    i2s.deinit()
+
+    # Print out test result, time should be in range of 500ms.
+    print(mode_str, bits_per_sample, channels, abs(dt - 500) <= 4)
+
+
+test(I2S.TX, 16, I2S.MONO)
+test(I2S.TX, 16, I2S.STEREO)
+test(I2S.TX, 32, I2S.MONO)
+test(I2S.TX, 32, I2S.STEREO)
+test(I2S.RX, 16, I2S.MONO)
+test(I2S.RX, 16, I2S.STEREO)
+test(I2S.RX, 32, I2S.MONO)
+test(I2S.RX, 32, I2S.STEREO)

tests/extmod/machine_i2s_rate.py.exp

@@ -0,0 +1,8 @@
+TX 16 1 True
+TX 16 2 True
+TX 32 1 True
+TX 32 2 True
+RX 16 1 True
+RX 16 2 True
+RX 32 1 True
+RX 32 2 True