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Merge pull request #66 from timchinowsky/add_pioasm_i2c_codec
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add codec example
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@FoamyGuy
FoamyGuy authored Sep 8, 2024
2 parents 357f933 + a9f20ea commit 341a234
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210 changes: 210 additions & 0 deletions examples/pioasm_i2s_codec.py
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# SPDX-FileCopyrightText: 2024 Tim Chinowsky
# SPDX-License-Identifier: MIT

import array
import board
import rp2pio

import adafruit_pioasm

# Implement extended multichannel I2S interface like that used by audio codecs
# such as the TAC5212. In extended I2S, "Left" and "Right" can each contain
# multiple channels, so for instance 8 channels of audio can be sent as a "left"
# containing 4 channels and a "right" containing 4 channels.

# In this implementation the number of bits per sample, sample rate, and
# number of channels can be independently specified. The number of channels must
# be even, to divide evenly between left and right.

# Ramped test data containing the requested number of sample sets (one set = one
# sample for each channel) and spanning the specified number of bits will be generated
# and sent out over I2S on the specified pins.

# Data will be preceded and followed by a set of zeros for convenience.
# (Some protocol analyzers have trouble analyzing serial data at the the beginning
# and end of a data set)

# At the same time that I2S data is sent out the out_pin, I2S data will be received
# on the in_pin. If the output is looped back (connected) to the input, the data
# received should be the same as the data sent.

# Some samples run in loopback configuration:

# bits per sample: 16
# sample rate: 48000
# channels: 4
# sample sets: 4

# actual sample frequency 47984.6 Hz
# bit clock 3071017.0 Hz

# write: 00000000 00000000 00000000 00000000
# read: 00000000 00000000 00000000 00000000

# write: 00000000 00001111 00002222 00003333
# read: 00000000 00001111 00002222 00003333

# write: 00004444 00005555 00006666 00007777
# read: 00004444 00005555 00006666 00007777

# write: 00008888 00009999 0000aaaa 0000bbbb
# read: 00008888 00009999 0000aaaa 0000bbbb

# write: 0000cccc 0000dddd 0000eeee 0000ffff
# read: 0000cccc 0000dddd 0000eeee 0000ffff

# write: 00000000 00000000 00000000 00000000
# read: 00000000 00000000 00000000 00000000

# bits per sample: 24
# sample rate: 24000
# channels: 8
# sample sets: 5

# actual sample frequency 23987.7 Hz
# bit clock 4605642.0 Hz

# write: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
# read: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

# write: 00000000 00069069 000d20d2 0013b13b 001a41a4 0020d20d 00276276 002df2df
# read: 00000000 00069069 000d20d2 0013b13b 001a41a4 0020d20d 00276276 002df2df

# write: 00348348 003b13b1 0041a41a 00483482 004ec4ec 00555554 005be5be 00627626
# read: 00348348 003b13b1 0041a41a 00483482 004ec4ec 00555554 005be5be 00627626

# write: 00690690 006f96f8 00762762 007cb7ca 00834834 0089d89c 00906904 0096f96c
# read: 00690690 006f96f8 00762762 007cb7ca 00834834 0089d89c 00906904 0096f96c

# write: 009d89d8 00a41a40 00aaaaa8 00b13b10 00b7cb7c 00be5be4 00c4ec4c 00cb7cb4
# read: 009d89d8 00a41a40 00aaaaa8 00b13b10 00b7cb7c 00be5be4 00c4ec4c 00cb7cb4

# write: 00d20d20 00d89d88 00df2df0 00e5be58 00ec4ec4 00f2df2c 00f96f94 00ffffff
# read: 00d20d20 00d89d88 00df2df0 00e5be58 00ec4ec4 00f2df2c 00f96f94 00ffffff

# write: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
# read: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000


def i2s_codec( # pylint: disable=too-many-arguments
channels=2,
sample_rate=48000,
bits=16,
bclk_pin=None,
out_pin=None,
in_pin=None,
):
i2s_clock = sample_rate * channels * bits
pio_clock = 4 * i2s_clock
pio_code = """
.program i2s_codec
.side_set 2
; at program start we initialize the bit count top
; (which may be >32) with data
; pulled from the input fifo
pull noblock ; first empty the input fifo
pull noblock
pull noblock
pull noblock
out null, 32 ; then clear OSR so we can get a new value
pull block ; then get the bit count top value from the fifo
; /--- LRCLK
; |/-- BCLK
; ||
mov x, osr; side 0b01 [1] ; save it in x
out null, 32 side 0b00 [1]
mov y, x side 0b01 [1] ; start of main loop (wrap target=8)
bitloop1:
out pins 1 side 0b00
in pins 1 side 0b00
jmp y-- bitloop1 side 0b01 [1]
out pins 1 side 0b10
in pins 1 side 0b10
mov y, x side 0b11 [1]
bitloop0:
out pins 1 side 0b10
in pins 1 side 0b10
jmp y-- bitloop0 side 0b11 [1]
out pins 1 side 0b00
in pins 1 side 0b00
"""
pio_params = {
"frequency": pio_clock,
"first_out_pin": out_pin,
"first_in_pin": in_pin,
"first_sideset_pin": bclk_pin,
"sideset_pin_count": 2,
"auto_pull": True,
"auto_push": True,
"out_shift_right": False,
"in_shift_right": False,
"pull_threshold": bits,
"push_threshold": bits,
"wait_for_txstall": False,
"wrap_target": 8,
}
pio_instructions = adafruit_pioasm.assemble(pio_code)
i2s_clock = sample_rate * channels * bits
pio_clock = 4 * i2s_clock
pio = rp2pio.StateMachine(pio_instructions, **pio_params)
return pio


def spaced_samples(length, bits):
max_int = (1 << bits) - 1
if length == 1:
return [0]
step = max_int / (length - 1)
result = [round(i * step) for i in range(length)]
result[0] = 0
result[-1] = max_int
return result


while True:
print()
BITS = int(input("# bits per sample: "))
SAMPLE_RATE = int(input("# sample rate: "))
CHANNELS = int(input("# channels: "))
SAMPLE_SETS = int(input("# sample sets: "))

n_samples = CHANNELS * SAMPLE_SETS
buffer_type = "L"
buffer_width = 32
data = [0] * CHANNELS + spaced_samples(n_samples, BITS) + [0] * CHANNELS
# initialize pio bit count top value by sending it at the start of output data
bit_count_top = BITS * (CHANNELS // 2) - 2
buffer_out = array.array(
buffer_type, [bit_count_top] + [d << (buffer_width - BITS) for d in data]
)
buffer_in = array.array(buffer_type, [0] * len(data))

PIO = i2s_codec(
channels=CHANNELS,
bits=BITS,
sample_rate=SAMPLE_RATE,
out_pin=board.D9,
in_pin=board.D10,
bclk_pin=board.D5, # L/R signal will be one pin higher, i.e. D6
)
print()
print(f"# actual sample frequency {PIO.frequency/4/CHANNELS/BITS:9.1f} Hz")
print(f"# bit clock {PIO.frequency/4:9.1f} Hz")
print()
PIO.write_readinto(buffer_out, buffer_in)
start = 0
line_length = CHANNELS

while start < len(buffer_in):
print("# write: ", end="")
for i in range(start, min(len(data), start + line_length)):
print(f"{data[i]:0{buffer_width/4}x} ", end=" ")
print()
print("# read: ", end="")
for i in range(start, min(len(buffer_in), start + line_length)):
print(f"{buffer_in[i]:0{buffer_width/4}x} ", end=" ")
print()
print()
start += line_length
PIO.deinit()
del PIO

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