PYNQ-Z2のPython上で音声ループバック https://twitter.com/kamiya_owl/status/1221407626564534277

audio_adau1761.cpp

// select_line_in()呼び出し時にTX Buffから音声出力できるようにレジスタ設定を書き込んでおく

/******************************************************************************
 * Function to select LINE_IN as input.
 * @param  iic_index is the i2c index in /dev list.
 * @return none.
 *****************************************************************************/
extern "C" void select_line_in(int iic_index) {
    int iic_fd;
    iic_fd = setI2C(iic_index, IIC_SLAVE_ADDR);
    if (iic_fd < 0) {
        printf("Unable to set I2C %d.\n", iic_index);
    }

    // Mixer 1  (left channel)
    write_audio_reg(R4_RECORD_MIXER_LEFT_CONTROL_0, 0x01, iic_fd);
    // Enable LAUX (MX1AUXG)
    write_audio_reg(R5_RECORD_MIXER_LEFT_CONTROL_1, 0x07, iic_fd);

    // Mixer 2
    write_audio_reg(R6_RECORD_MIXER_RIGHT_CONTROL_0, 0x01, iic_fd);
    // Enable RAUX (MX2AUXG)
    write_audio_reg(R7_RECORD_MIXER_RIGHT_CONTROL_1, 0x07, iic_fd);

    /* ついでに出力も使えるようにする */

    // Enable Mixer3 and Mixer4
    write_audio_reg(R22_PLAYBACK_MIXER_LEFT_CONTROL_0, 0x21, iic_fd);
    write_audio_reg(R24_PLAYBACK_MIXER_RIGHT_CONTROL_0, 0x41, iic_fd);
    // Enable Left/Right Headphone out
    write_audio_reg(R29_PLAYBACK_HEADPHONE_LEFT_VOLUME_CONTROL, 0xE7, iic_fd);
    write_audio_reg(R30_PLAYBACK_HEADPHONE_RIGHT_VOLUME_CONTROL, 0xE7, iic_fd);


    if (unsetI2C(iic_fd) < 0) {
        printf("Unable to unset I2C %d.\n", iic_index);
    }
}

echo_audio.py

from pynq.overlays.base import BaseOverlay
base = BaseOverlay("base.bit", download=False)

# from audio_adau1761.h
I2S_DATA_RX_L_REG = 0x00
I2S_DATA_RX_R_REG = 0x04
I2S_DATA_TX_L_REG = 0x08
I2S_DATA_TX_R_REG = 0x0C
I2S_STATUS_REG    = 0x10

pAudio = base.audio
pAudio.select_line_in() # line入力を使う

while True:
    l_raw = pAudio.mmio.read_reg(offset=I2S_DATA_RX_L_REG)
    r_raw = pAudio.mmio.read_reg(offset=I2S_DATA_RX_R_REG)
    pAudio.mmio.write_reg(data=l_raw, offset=I2S_DATA_TX_L_REG)
    pAudio.mmio.write_reg(data=r_raw, offset=I2S_DATA_TX_R_REG)