Using I2SC (Inter-IC Sound Controller)

Last modified by Microchip on 2025/02/28 15:10

Introduction

This page explains how to enable and configure I2SC from SAMA5D2 and SAM9X60 SoCs to an external codec, using MikroElektronika audio codec PROTO board as an example.

The Inter-IC Sound Controller (I2SC) provides a 5-wire, bidirectional, synchronous, digital audio link to external audio devices: I2SC_DI(ADCDAT), I2SC_DO(DACDAT), I2SC_WS(LRCLK), I2SC_CK(BCLK), and I2SC_MCK(MCLK) pins.

Characteristics:

Master, Slave, and Controller Modes
- Slave: Data Received/Transmitted
- Master: Data Received/Transmitted And Clocks Generated
- Controller: Clocks Generated
Individual Enable and Disable of Receiver, Transmitter and Clocks
Configurable Clock Generator Common to Receiver and Transmitter
- Suitable for a Wide Range of Sample Frequencies (f s ), Including 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, and 192 kHz
- 32 f s to 1024 f s Master Clock Generated for External Oversampling Data Converters
Support for Multiple Data Formats
- 32-, 24-, 20-, 18-, 16-, and 8-bit Mono or Stereo Format
- 16- and 8-bit Compact Stereo Format, with Left and Right Samples Packed in the Same Word to Reduce Data Transfers
DMA Controller Interfaces the Receiver and Transmitter to Reduce Processor Overhead
- One DMA Controller Channel for Both Audio Channels
Smart Holding Registers Management to Avoid Audio Channels Mix After Overrun or Underrun
For SAM9X60 only:
- 1- to 8-channel Time Division Multiplexed (TDM) with Frame Synchronization

MikroElektronika PROTO Audio Codec Board

The PROTO board can be used to test capture and playback on I2SC. More details regarding this board can be found on https://www.mikroe.com/audio-codec-proto-board

Prerequisites

Linux4sam 5.8 or newer or vanilla kernel 4.18 (driver only) or newer;
- kernel must be compiled with SND_SOC_MIKROE_PROTO
available only on SAMA5D2 and SAM9X60 SoCs;
- SAMA5D2 SoC can be tested with SAMA5D2 Xplained board:

Controller	I2S wire	board connector
i2s0	I2SC_MCK	J17 - 23
	I2SC_CK	J17 - 17
	I2SC_WS	J17 - 22
	I2SC_DO	J17 - 25
	I2SC_DI	J17 - 26
i2s1	I2SC_MCK	J17 - 4
	I2SC_CK	J17 - 5
	I2SC_WS	J8 - 1
	I2SC_DO	J9 - 3
	I2SC_DI	J9 - 2

- SAM9X60 SoC can be tested with SAM9X60-EK board:

Controller	I2S wire	board connector
i2s	I2SMCC_MCK	J16 - 7
	I2SMCC_CK	J16 - 12
	I2SMCC_WS	J16 - 35
	I2SMCC_DO	J16 - 40
	I2SMCC_DI	J16 - 38

Wire setup

The I2SC pins must be connected to the codec in the following way:

I2SC	PROTO codec
I2SC_CK	SCK
I2SC_DI	MISO
I2SC_DO	MOSI
I2SC_WS	ADCL (for capture)
I2SC_WS	DACL (for playback)

Also, you will need to connect PROTO SDA (Data Input) and SCL (Clock Input) pins to a TWI interface.

Bellow you can see a picture with the I2SC0 and I2C0 connected to the PROTO board:

On Linux4sam 6.0 release, the i2s0_proto overlay can be used for the setup in the picture. For this overlay, the PROTO SDA and SCL need to be connected to the board's i2c0 bus:

PROTO codec	board connector
SDA	J8 – 5 (A4)
SCL	J8 – 6 (A5)

Boot with the following u-boot command:

=> bootm 0x24000000#kernel_dtb#i2s0_proto
## Loading kernel from FIT Image at 24000000 ...
   Using 'kernel_dtb' configuration
   Trying 'kernel' kernel subimage
     Description:  Linux4SAM Linux kernel
     Type:         Kernel Image
     Compression:  uncompressed
     Data Start:   0x240000e0
     Data Size:    3835928 Bytes = 3.7 MiB
     Architecture: ARM
     OS:           Linux
     Load Address: 0x22000000
     Entry Point:  0x22000000
     Hash algo:    crc32
     Hash value:   7fca0b0c
     Hash algo:    sha1
     Hash value:   45cbd1fe15c283ef26056917fb4e10e2ce6b30e4
   Verifying Hash Integrity ... crc32+ sha1+ OK
## Loading fdt from FIT Image at 24000000 ...
   Using 'kernel_dtb' configuration
   Trying 'base_fdt' fdt subimage
     Description:  Flattened Device Tree blob
     Type:         Flat Device Tree
     Compression:  uncompressed
     Data Start:   0x243a8a24
     Data Size:    44591 Bytes = 43.5 KiB
     Architecture: ARM
     Load Address: 0x23000000
     Hash algo:    crc32
     Hash value:   9c933a6d
     Hash algo:    sha1
     Hash value:   c249364df161f1158f084ab0191c034a519a9fdd
   Verifying Hash Integrity ... crc32+ sha1+ OK
   Loading fdt from 0x243a8a24 to 0x23000000
## Loading fdt from FIT Image at 24000000 ...
   Using 'i2s0_proto' configuration
   Trying 'fdt_i2s0_proto' fdt subimage
     Description:  Device Tree blob PROTO Audio board overlay
     Type:         Flat Device Tree
     Compression:  uncompressed
     Data Start:   0x243b9b64
     Data Size:    1066 Bytes = 1 KiB
     Architecture: ARM
     Load Address: 0x23170000
     Hash algo:    crc32
     Hash value:   38a511f6
     Hash algo:    sha1
     Hash value:   74d5c3996811a9307097969d8fe3c5e63b9973a0
   Verifying Hash Integrity ... crc32+ sha1+ OK
   Loading fdt from 0x243b9b64 to 0x23170000
   Booting using the fdt blob at 0x23000000
   Loading Kernel Image ... OK
   Loading Device Tree to 3fb47000, end 3fb54f5f ... OK

Starting kernel ...

Make sure the output of the bootm command is the same as above and that fdt_i2s0_proto overlay is applied .

For SAM9X60, the overlay can be found at i2s_proto overlay, and #i2s_proto needs to be used instead. The PROTO SDA and SCL need to be connected to the board's i2c0 bus:

PROTO codec	board connector
SDA	J16 – 3 (PA0)
SCL	J16 – 5 (PA1)

Probing

If everything works well, at linux boot look for:

ALSA device list:
[...]
#2: wm8731 @ sama5d2_xplained

Another step to assure that we are using the right device is to search /proc file system:

# cat /proc/asound/pcm | grep -i wm8731
02-00: WM8731 HiFi wm8731-hifi-0 :  : playback 1 : capture 1

These steps are necessary to see if the drivers probed and to get the ALSA device id. In both prints, it is the first number on the line: 2 in our example. Also, we will need to find our complete device name:

# aplay -L
[...]
sysdefault:CARD=sama5d2xplain_1
wm8731 @ sama5d2_xplained, 
Default Audio Device

In this list, our board is the one with the wm8731 codec. In our case, the device’s name is: sysdefault:sama5d2xplain_1

Playback

First, we need to use amixer (or alsamixer) to enable the playback. We must enable 'Output Mixer HiFi Playback Switch' (replace –c 2 with your –c <ALSA device id>):

# amixer -c 2 cset name='Output Mixer HiFi Playback Switch' on

And we should see:

numid=13,iface=MIXER,name='Output Mixer HiFi Playback Switch'
; type=BOOLEAN,access=rw------,values=1
: values=on

Before starting the playback, make sure that the I2SC_WS pin is connected to the DACL pin.

Insert headphones in the playback jack and check sound on both channels (replace -Dsysdefault:sama5d2xplain_1 with your device’s name):

# speaker-test -Dsysdefault:sama5d2xplain_1 -c 2

Capture

Use amixer (or alsamixer) to enable sound recording (replace –c 2 with your –c <ALSA device id>):

# amixer -c 2 cset name='Input Mux' 1
numid=14,iface=MIXER,name='Input Mux'
; type=ENUMERATED,access=rw------,values=1,items=2
; Item #0 'Line In'
; Item #1 'Mic'
: values=1# amixer -c 2 cset name='Mic Capture Switch' on
numid=6,iface=MIXER,name='Mic Capture Switch'
; type=BOOLEAN,access=rw------,values=1
: values=on

Before starting the record, make sure that the I2SC_WS pin is connected to the ADCL pin.

Connect a PC or a low impedance microphone to the Mic jack and start recording (replace –Dplughw:2 with your –Dplughw:<ALSA device id>):

# arecord -Dplughw:2 -c 2 -f S16_LE out.wav

Stop the recording after a few seconds and playback the resulting out.wav file. Make sure sound is on both channels (replace –Dplughw:2 with your –Dplughw:<ALSA device id>)

Before starting the playback, make sure that the I2SC_WS pin is connected to the DACL pin

# aplay -Dplughw:2 out.wav

For other questions regarding audio configurations and setup please see Audio FAQ.

Using I2SC (Inter-IC Sound Controller)

Introduction

MikroElektronika PROTO Audio Codec Board

Prerequisites

Wire setup

Probing

Playback

Capture

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Summary

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