Generic audio driver to use the I2S interface of the Raspberry Pi for sound output to a dsp

This repo includes the files to setup the I²S-Interface of the Raspberry Pi to use it as a generic audio output (digital soundcard). All devices which don't need any configuration or initialisation via I²C or SPI can be connected. Possible devices are DACs and DSPs which work at a fixed sample rate (and don't have an ASRC). One of the most pupular devices is the ADAU1701 SigmaDSP from Analog Devices. The following configuration will be explained based on the ADAU1701.

The installation guide is available on my website: https://digital-audio-labs.jimdofree.com/english/raspberry-pi/adau1701-i2s-driver/.

The testproject is a Sigma Studio project file to test the digital IO-ports of the ADAU1701. Therefore a sine wave is generated, output on MP6, fed back to MP0 and output to the DAC. The aim is to check whether the config of the pins and the wireing of the dsp are correct.

Pin 12 (PCM_CLK) - MP5 and MP11

Pin 35 (PCM_FS) - MP4 and MP10

Pin 40 (PCM_DOUT) - MP0 (or MP1, MP2, MP3)

Pin 39 (GND) - any GND-pin

Codec: master mode (clocks provided from external oscillator)

Format: I2S

BCLK = 2 * 32 * Fs = 64 * Fs = 3.072 MHz

LRCLK = Fs

Sample rate: 48 kHz

Bit depth: 24 bit

Data format: I2S

MCLK = 256 * Fs = 12.288 MHz

BCLK = 64 * Fs = 3.072 MHz --> Internal / 16

LRCLK = Fs --> Internal / 1024

LRCLK polarity: falling edge (LRCLK = 0 = left channel, LRCLK = 1 = right channel)

BCLK data change: falling edge

Transmission: MSB first

MSB position: delayed by 1 BCLK