class I2S – Inter-IC Sound bus protocol¶
I2S is a synchronous serial protocol used to connect digital audio devices. At the physical level, a bus consists of 3 lines: SCK, WS, SD. The I2S class supports Master operation. Slave operation is not supported.
The I2S class is currently available as a Technical Preview. During the preview period, feedback from users is encouraged. Based on this feedback, the I2S class API and implementation may be changed.
I2S objects can be created and initialized using:
from machine import I2S from machine import Pin # ESP32 sck_pin = Pin(14) # Serial clock output ws_pin = Pin(13) # Word clock output sdout_pin = Pin(12) # Serial data output or # PyBoards sck_pin = Pin("Y6") # Serial clock output ws_pin = Pin("Y5") # Word clock output sdout_pin = Pin("Y8") # Serial data output audio_out = I2S(2, sck=sck_pin, ws=ws_pin, sdin=sdin_pin, mode=I2S.TX, bits=16, format=I2S.MONO, rate=44100, ibuf=20000) audio_in = I2S(2, sck=sck_pin, ws=ws_pin, sdin=sdin_pin, mode=I2S.RX, bits=32, format=I2S.STEREO, rate=22050, ibuf=20000)
- 3 modes of operation are supported:
num_written = audio_out.write(buf) # blocks until buf emptied num_read = audio_in.readinto(buf) # blocks until buf filled
audio_out.irq(i2s_callback) # i2s_callback is called when buf is emptied num_written = audio_out.write(buf) # returns immediately audio_in.irq(i2s_callback) # i2s_callback is called when buf is filled num_read = audio_in.readinto(buf) # returns immediately
swriter = uasyncio.StreamWriter(audio_out) swriter.write(buf) await swriter.drain() sreader = uasyncio.StreamReader(audio_in) num_read = await sreader.readinto(buf)
I2S(id, *, sck, ws, sd, mode, bits, format, rate, ibuf)¶
Construct an I2S object of the given id:
ididentifies a particular I2S bus.
idis board and port specific:
PYBv1.0/v1.1: has one I2S bus with id=2.
PYBD-SFxW: has two I2S buses with id=1 and id=2.
ESP32: has two I2S buses with id=0 and id=1.
Keyword-only parameters that are supported on all ports:
sckis a pin object for the serial clock line
wsis a pin object for the word select line
sdis a pin object for the serial data line
modespecifies receive or transmit
bitsspecifies sample size (bits), 16 or 32
formatspecifies channel format, STEREO or MONO
ratespecifies audio sampling rate (samples/s)
ibufspecifies internal buffer length (bytes)
For all ports, DMA runs continuously in the background and allows user applications to perform other operations while sample data is transfered between the internal buffer and the I2S peripheral unit. Increasing the size of the internal buffer has the potential to increase the time that user applications can perform non-I2S operations before underflow (e.g.
writemethod) or overflow (e.g.
see Constructor for argument descriptions
Deinitialize the I2S bus
Read audio samples into the buffer specified by
bufmust support the buffer protocol, such as bytearray or array. “buf” byte ordering is little-endian. For Stereo format, left channel sample precedes right channel sample. For Mono format, the left channel sample data is used. Returns number of bytes read
Write audio samples contained in
bufmust support the buffer protocol, such as bytearray or array. “buf” byte ordering is little-endian. For Stereo format, left channel sample precedes right channel sample. For Mono format, the sample data is written to both the right and left channels. Returns number of bytes written
Set a callback.
handleris called when
bufis emptied (
writemethod) or becomes full (
readintomethod). Setting a callback changes the
readintomethods to non-blocking operation.
handleris called in the context of the MicroPython scheduler.
shift(buf, bits, shift)¶
bitwise shift of all samples contained in
bitsspecifies sample size in bits.
shiftspecifies the number of bits to shift each sample. Positive for left shift, negative for right shift. Typically used for volume control. Each bit shift changes sample volume by 6dB.