I2S

The Rhino Pi IQ9N provides 1 I2S digital audio interface, using the WAFER-GH1.25-4PLB connector.

Interface Definition

For the position of the I2S interface on the board, see the interface layout diagram in Rhino Pi IQ9N Interface Description on the first page.

Pin	Signal	Description
1	DATA	Audio data
2	SCK	Bit clock
3	WS	Channel select (frame sync)
4	GND	Ground

This interface outputs I2S digital audio signals, so an external DAC or codec chip with I2S input is required to drive speakers.

Audio System Overview

Item	Description
Onboard audio	2 × 5W Speaker, output through the SPK interface
Array microphone	4Mic Array omnidirectional microphone
AEC	Supports echo cancellation; must be used together with the internal USB2.0 audio interface

For wiring instructions for the speakers and microphone, see Audio Test.

Viewing Sound Cards and Devices

aplay -l
arecord -l

Playing Audio

Use aplay to play a WAV file:

aplay -D hw:0,0 test.wav

Specify the sound card and device:

aplay -D plughw:<card>,<device> test.wav

Recording Audio

arecord -D hw:0,0 -f S16_LE -r 48000 -c 2 -d 5 rec.wav

Parameter description:

Parameter	Description
-f S16_LE	16-bit little-endian sample format
-r 48000	Sample rate 48 kHz
-c 2	Stereo
-d 5	Recording duration 5 seconds

Configuring the Default Sound Card

View the list of available sound cards:

cat /proc/asound/cards

To set the default sound card, edit /etc/asound.conf:

defaults.pcm.card 0
defaults.ctl.card 0

Example: Reading I2S Microphone Data (Python)

import wave
import pyaudio

FORMAT = pyaudio.paInt16
CHANNELS = 2
RATE = 48000
CHUNK = 1024
SECONDS = 5

p = pyaudio.PyAudio()
stream = p.open(
    format=FORMAT,
    channels=CHANNELS,
    rate=RATE,
    input=True,
    frames_per_buffer=CHUNK,
)

frames = []
for _ in range(int(RATE / CHUNK * SECONDS)):
    frames.append(stream.read(CHUNK))

stream.stop_stream()
stream.close()
p.terminate()

with wave.open("rec.wav", "wb") as wf:
    wf.setnchannels(CHANNELS)
    wf.setsampwidth(p.get_sample_size(FORMAT))
    wf.setframerate(RATE)
    wf.writeframes(b"".join(frames))

Installing the dependency:

sudo apt install -y python3-pyaudio

Notes

• The interface is 3.3V level; external devices must support 3.3V I2S timing.
• When connecting an external I2S device, confirm whether it is in slave or master mode to avoid clock direction conflicts.
• Parameters such as sample rate and bit width must match the capabilities of the slave device, otherwise noise or silence will result.
• For wiring and interface position descriptions, see Debug & Expansion Interfaces.