I2S

[English]

简介

I2S(Inter-IC Sound,集成电路内置音频总线)是一种同步串行通信协议,通常用于在两个数字音频设备之间传输音频数据。

ESP32 包含 2 个 I2S 外设。通过配置这些外设,可以借助 I2S 驱动来输入和输出采样数据。

标准或 TDM 通信模式下的 I2S 总线包含以下几条线路:

  • MCLK:主时钟线。该信号线可选,具体取决于从机,主要用于向 I2S 从机提供参考时钟。

  • BCLK:位时钟线。用于数据线的位时钟。

  • WS:字(声道)选择线。通常用于识别声道(除 PDM 模式外)。

  • DIN/DOUT:串行数据输入/输出线。如果 DIN 和 DOUT 被配置到相同的 GPIO,数据将在内部回环。

PDM 通信模式下的 I2S 总线包含以下几条线路:

  • CLK:PDM 时钟线。

  • DIN/DOUT:串行数据输入/输出线。

每个 I2S 控制器都具备以下功能,可由 I2S 驱动进行配置:

  • 可用作系统主机或从机

  • 可用作发射器或接收器

  • DMA 控制器支持流数据采样,CPU 无需单独复制每个采样数据

每个控制器都支持 RX 或 TX 单工通信。由于 RX 与 TX 通道共用一个时钟,因此只有在两者拥有相同配置时,才可以实现全双工通信。

I2S 文件结构

I2S 文件结构

I2S 文件结构

需要包含在 I2S 应用中的公共头文件如下所示:

  • i2s.h:提供原有 I2S API(用于使用原有驱动的应用)。

  • i2s_std.h:提供标准通信模式的 API(用于使用标准模式的新驱动程序的应用)。

  • i2s_pdm.h:提供 PDM 通信模式的 API(用于使用 PDM 模式的新驱动程序的应用)。

  • i2s_tdm.h:提供 TDM 通信模式的 API(用于使用 TDM 模式的新驱动的应用)。

备注

原有驱动与新驱动无法共存。包含 i2s.h 以使用原有驱动,或包含其他三个头文件以使用新驱动。原有驱动未来可能会被删除。

已包含在上述头文件中的公共头文件如下所示:

  • i2s_types_legacy.h:提供只在原有驱动中使用的原有公共类型。

  • i2s_types.h:提供公共类型。

  • i2s_common.h:提供所有通信模式通用的 API。

I2S 时钟

时钟源

  • i2s_clock_src_t::I2S_CLK_SRC_DEFAULT:默认 PLL 时钟。

  • i2s_clock_src_t::I2S_CLK_SRC_PLL_160M:160 MHz PLL 时钟。

  • i2s_clock_src_t::I2S_CLK_SRC_APLL:音频 PLL 时钟,在高采样率应用中比 I2S_CLK_SRC_PLL_160M 更精确。其频率可根据采样率进行配置,但如果 APLL 已经被 EMAC 或其他通道占用,则无法更改 APLL 频率,驱动程序将尝试在原有 APLL 频率下工作。如果原有 APLL 频率无法满足 I2S 的需求,时钟配置将失败。

时钟术语

  • 采样率:单声道每秒采样数据数量。

  • SCLK:源时钟频率,即时钟源的频率。

  • MCLK:主时钟频率,BCLK 由其产生。MCLK 信号通常作为参考时钟,用于同步 I2S 主机和从机之间的 BCLK 和 WS。

  • BCLK:位时钟频率,一个 BCLK 时钟周期代表数据管脚上的一个数据位。通过 i2s_std_slot_config_t::slot_bit_width 配置的通道位宽即为一个声道中的 BCLK 时钟周期数量,因此一个声道中可以有 8/16/24/32 个 BCLK 时钟周期。

  • LRCK / WS:左/右时钟或字选择时钟。在非 PDM 模式下,其频率等于采样率。

备注

通常,MCLK 应该同时是 采样率 和 BCLK 的倍数。字段 i2s_std_clk_config_t::mclk_multiple 表示 MCLK 相对于 采样率 的倍数。在大多数情况下,将其设置为 I2S_MCLK_MULTIPLE_256 即可。但如果 slot_bit_width 被设置为 I2S_SLOT_BIT_WIDTH_24BIT,为了保证 MCLK 是 BCLK 的整数倍,应该将 i2s_std_clk_config_t::mclk_multiple 设置为能被 3 整除的倍数,如 I2S_MCLK_MULTIPLE_384,否则 WS 会不精准。

I2S 通信模式

模式概览

芯片

I2S 标准

PDM TX

PDM RX

TDM

ADC/DAC

LCD/摄像头

ESP32

I2S 0/1

I2S 0

I2S 0

I2S 0

I2S 0

ESP32-S2

I2S 0

I2S 0

ESP32-C3

I2S 0

I2S 0

I2S 0

ESP32-C6

I2S 0

I2S 0

I2S 0

ESP32-S3

I2S 0/1

I2S 0

I2S 0

I2S 0/1

ESP32-H2

I2S 0

I2S 0

I2S 0

ESP32-P4

I2S 0~2

I2S 0

I2S 0

I2S 0~2

ESP32-C5

I2S 0

I2S 0

I2S 0

标准模式

标准模式中有且仅有左右两个声道,驱动中将声道称为 slot。这些声道可以支持 8/16/24/32 位宽的采样数据,声道的通信格式主要包括以下几种:

  • Philips 格式:数据信号与 WS 信号相比有一个位的位移。WS 信号的占空比为 50%。

  • MSB 格式:与 Philips 格式基本相同,但其数据没有位移。

  • PCM 帧同步:数据有一个位的位移,同时 WS 信号变成脉冲,持续一个 BCLK 周期。

PDM 模式 (TX)

在 PDM(Pulse-density Modulation,脉冲密度调制)模式下,TX 通道可以将 PCM 数据转换为 PDM 格式,该格式始终有左右两个声道。PDM TX 只在 I2S0 中受支持,且只支持 16 位宽的采样数据。PDM TX 至少需要一个 CLK 管脚用于时钟信号,一个 DOUT 管脚用于数据信号(即下图中的 WS 和 SD 信号。BCK 信号为内部位采样时钟,在 PDM 设备之间不需要)。PDM 模式允许用户配置上采样参数 i2s_pdm_tx_clk_config_t::up_sample_fpi2s_pdm_tx_clk_config_t::up_sample_fs,上采样率可以通过公式 up_sample_rate = i2s_pdm_tx_clk_config_t::up_sample_fp / i2s_pdm_tx_clk_config_t::up_sample_fs 来计算。在 PDM TX 中有以下两种上采样模式:

  • 固定时钟频率模式:在这种模式下,上采样率将根据采样率的变化而变化。设置 fp = 960fs = sample_rate / 100,则 CLK 管脚上的时钟频率 (Fpdm) 将固定为 128 * 48 KHz = 6.144 MHz。注意此频率不等于采样率 (Fpcm)。

  • 固定上采样率模式:在这种模式下,上采样率固定为 2。设置 fp = 960fs = 480,则 CLK 管脚上的时钟频率 (Fpdm) 将为 128 * sample_rate

PDM 模式 (RX)

在 PDM(Pulse-density Modulation,脉冲密度调制)模式下,RX 通道可以接收 PDM 格式的数据并将数据转换成 PCM 格式。PDM RX 只在 I2S0 中受支持,且只支持 16 位宽的采样数据。PDM RX 至少需要一个 CLK 管脚用于时钟信号,一个 DIN 管脚用于数据信号。此模式允许用户配置下采样参数 i2s_pdm_rx_clk_config_t::dn_sample_mode。在 PDM RX 中有以下两种下采样模式:

LCD/摄像头模式

LCD/摄像头模式只支持在 I2S0 上通过并行总线运行。在 LCD 模式下,I2S0 应当设置为主机 TX 模式;在摄像头模式下,I2S0 应当设置为从机 RX 模式。这两种模式不是由 I2S 驱动实现的,关于 LCD 模式的实现,请参阅 I80 Interfaced LCD。更多信息请参考 ESP32 技术参考手册 > I2S 控制器 (I2S) > LCD 模式 [PDF]。

ADC/DAC 模式

仅 ESP32 支持在 I2S0 上运行 ADC 和 DAC 模式。实际上,ADC 和 DAC 模式是 LCD/摄像头模式的两个子模式。I2S0 可以直接路由到内部模数转换器 (ADC) 和数模转换器 (DAC),也即 ADC 和 DAC 外设可以通过 I2S0 的 DMA 连续读取或写入数据。由于 ADC 和 DAC 并非通信模式,因此并没有在 I2S 驱动中实现。

功能概览

I2S 驱动提供以下服务:

资源管理

I2S 驱动中的资源可分为三个级别:

  • 平台级资源:当前芯片中所有 I2S 控制器的资源。

  • 控制器级资源:一个 I2S 控制器的资源。

  • 通道级资源:一个 I2S 控制器 TX 或 RX 通道的资源。

公开的 API 都是通道级别的 API,通道句柄 i2s_chan_handle_t 可以帮助用户管理特定通道下的资源,而无需考虑其他两个级别的资源。高级别资源为私有资源,由驱动自动管理。用户可以调用 i2s_new_channel() 来分配通道句柄,或调用 i2s_del_channel() 来删除该句柄。

电源管理

电源管理启用(即开启 CONFIG_PM_ENABLE)时,系统将在进入 Light-sleep 前调整或停止 I2S 时钟源,这可能会影响 I2S 信号,从而导致传输或接收的数据无效。

I2S 驱动可以获取电源管理锁,从而防止系统设置更改或时钟源被禁用。时钟源为 APB 时,锁的类型将被设置为 esp_pm_lock_type_t::ESP_PM_APB_FREQ_MAX。时钟源为 APLL(若支持)时,锁的类型将被设置为 esp_pm_lock_type_t::ESP_PM_NO_LIGHT_SLEEP。用户通过 I2S 读写时(即调用 i2s_channel_read()i2s_channel_write()),驱动程序将获取电源管理锁,并在读写完成后释放锁。

有限状态机

I2S 通道有三种状态,分别为 registered(已注册)ready(准备就绪)running(运行中),它们的关系如下图所示:

I2S 有限状态机

I2S 有限状态机

图中的 <mode> 可用相应的 I2S 通信模式来代替,如 std 代表标准的双声道模式。更多关于通信模式的信息,请参考 I2S 通信模式 小节。

数据传输

I2S 的数据传输(包括数据发送和接收)由 DMA 实现。在传输数据之前,请调用 i2s_channel_enable() 来启用特定的通道。发送或接收的数据达到 DMA 缓冲区的大小时,将触发 I2S_OUT_EOFI2S_IN_SUC_EOF 中断。注意,DMA 缓冲区的大小不等于 i2s_chan_config_t::dma_frame_num,这里的一帧是指一个 WS 周期内的所有采样数据。因此, dma_buffer_size = dma_frame_num * slot_num * slot_bit_width / 8。传输数据时,可以调用 i2s_channel_write() 来输入数据,并把数据从源缓冲区复制到 DMA TX 缓冲区等待传输完成。此过程将重复进行,直到发送的字节数达到配置的大小。接收数据时,用户可以调用函数 i2s_channel_read() 来等待接收包含 DMA 缓冲区地址的消息队列,从而将数据从 DMA RX 缓冲区复制到目标缓冲区。

i2s_channel_write()i2s_channel_read() 都是阻塞函数,在源缓冲区的数据发送完毕前,或是整个目标缓冲区都被加载数据占用时,它们会一直保持等待状态。在等待时间达到最大阻塞时间时,返回 ESP_ERR_TIMEOUT 错误。要实现异步发送或接收数据,可以通过 i2s_channel_register_event_callback() 注册回调,随即便可在回调函数中直接访问 DMA 缓冲区,无需通过这两个阻塞函数来发送或接收数据。但请注意,该回调是一个中断回调,不要在该回调中添加复杂的逻辑、进行浮点运算或调用不可重入函数。

配置

用户可以通过调用相应函数(即 i2s_channel_init_std_mode()i2s_channel_init_pdm_rx_mode()i2s_channel_init_pdm_tx_mode()i2s_channel_init_tdm_mode())将通道初始化为特定模式。如果初始化后需要更新配置,必须先调用 i2s_channel_disable() 以确保通道已经停止运行,然后再调用相应的 'reconfig' 函数,例如 i2s_channel_reconfig_std_slot()i2s_channel_reconfig_std_clock()i2s_channel_reconfig_std_gpio()

IRAM 安全

默认情况下,由于写入或擦除 flash 等原因导致 cache 被禁用时,I2S 中断将产生延迟,无法及时执行 EOF 中断。

在实时应用中,可通过启用 Kconfig 选项 CONFIG_I2S_ISR_IRAM_SAFE 来避免此种情况发生,启用后:

  1. 即使在 cache 被禁用的情况下,中断仍可继续运行。

  2. 驱动程序将存放进 DRAM 中(以防其意外映射到 PSRAM 中)。

启用该选项可以保证 cache 禁用时的中断运行,但会相应增加 IRAM 占用。

线程安全

驱动程序可保证所有公开的 I2S API 的线程安全,使用时,可以直接从不同的 RTOS 任务中调用此类 API,无需额外锁保护。注意,I2S 驱动使用 mutex 锁来保证线程安全,因此不允许在 ISR 中使用这些 API。

Kconfig 选项

应用实例

I2S 驱动例程请参考 peripherals/i2s 目录。以下为每种模式的简单用法:

标准 TX/RX 模式的应用

不同声道的通信格式可通过以下标准模式的辅助宏来生成。如上所述,在标准模式下有三种格式,辅助宏分别为:

时钟配置的辅助宏为:

请参考 标准模式 了解 STD API 的相关信息。更多细节请参考 esp_driver_i2s/include/driver/i2s_std.h

STD TX 模式

以 16 位数据位宽为例,如果 uint16_t 写缓冲区中的数据如下所示:

数据 0

数据 1

数据 2

数据 3

数据 4

数据 5

数据 6

数据 7

...

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

...

下表展示了在不同 i2s_std_slot_config_t::slot_modei2s_std_slot_config_t::slot_mask 设置下线路上的真实数据。

数据位宽

声道模式

声道掩码

WS 低电平

WS 高电平

WS 低电平

WS 高电平

WS 低电平

WS 高电平

WS 低电平

WS 高电平

16 位

单声道

0x0002

0x0000

0x0001

0x0000

0x0004

0x0000

0x0003

0x0000

0x0000

0x0002

0x0000

0x0001

0x0000

0x0004

0x0000

0x0003

左右

0x0002

0x0002

0x0001

0x0001

0x0004

0x0004

0x0003

0x0003

立体声

0x0001

0x0001

0x0003

0x0003

0x0005

0x0005

0x0007

0x0007

0x0002

0x0002

0x0004

0x0004

0x0006

0x0006

0x0008

0x0008

左右

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

备注

当数据位宽为 32 位时,情况与上表类似,但当位宽为 8 位和 24 位时需要额外注意。数据位宽为 8 时,写入的缓冲区仍应使用 uint16_t (即以 2 字节对齐),并且只有高 8 位有效,低 8 位将被丢弃;数据位宽为 24 时,缓冲区应该使用 uint32_t ( 即以 4 字节对齐),并且只有高 24 位有效,低 8 位将被丢弃。

另外,在 8 位宽和 16 位宽单声道模式下,线路上的真实数据顺序会被调换。为了获取正确的数据顺序,写入缓冲区时,每两个字节需要调换一次数据顺序。

#include "driver/i2s_std.h"
#include "driver/gpio.h"

i2s_chan_handle_t tx_handle;
/* 通过辅助宏获取默认的通道配置
 * 这个辅助宏在 'i2s_common.h' 中定义,由所有 I2S 通信模式共享
 * 它可以帮助指定 I2S 角色和端口 ID */
i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_AUTO, I2S_ROLE_MASTER);
/* 分配新的 TX 通道并获取该通道的句柄 */
i2s_new_channel(&chan_cfg, &tx_handle, NULL);

/* 进行配置,可以通过宏生成声道配置和时钟配置
 * 这两个辅助宏在 'i2s_std.h' 中定义,只能用于 STD 模式
 * 它们可以帮助初始化或更新声道和时钟配置 */
i2s_std_config_t std_cfg = {
    .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(48000),
    .slot_cfg = I2S_STD_MSB_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_32BIT, I2S_SLOT_MODE_STEREO),
    .gpio_cfg = {
        .mclk = I2S_GPIO_UNUSED,
        .bclk = GPIO_NUM_4,
        .ws = GPIO_NUM_5,
        .dout = GPIO_NUM_18,
        .din = I2S_GPIO_UNUSED,
        .invert_flags = {
            .mclk_inv = false,
            .bclk_inv = false,
            .ws_inv = false,
        },
    },
};
/* 初始化通道 */
i2s_channel_init_std_mode(tx_handle, &std_cfg);

/* 在写入数据之前,先启用 TX 通道 */
i2s_channel_enable(tx_handle);
i2s_channel_write(tx_handle, src_buf, bytes_to_write, bytes_written, ticks_to_wait);

/* 如果需要更新声道或时钟配置
 * 需要在更新前先禁用通道 */
// i2s_channel_disable(tx_handle);
// std_cfg.slot_cfg.slot_mode = I2S_SLOT_MODE_MONO; // 默认为立体声
// i2s_channel_reconfig_std_slot(tx_handle, &std_cfg.slot_cfg);
// std_cfg.clk_cfg.sample_rate_hz = 96000;
// i2s_channel_reconfig_std_clock(tx_handle, &std_cfg.clk_cfg);

/* 删除通道之前必须先禁用通道 */
i2s_channel_disable(tx_handle);
/* 如果不再需要句柄,删除该句柄以释放通道资源 */
i2s_del_channel(tx_handle);

STD RX 模式

例如,当数据位宽为 16 时,如线路上的数据如下所示:

WS 低电平

WS 高电平

WS 低电平

WS 高电平

WS 低电平

WS 高电平

WS 低电平

WS 高电平

...

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

...

不同 i2s_std_slot_config_t::slot_modei2s_std_slot_config_t::slot_mask 配置下缓冲区中收到的数据如下所示。

数据位宽

声道模式

声道掩码

数据 0

数据 1

数据 2

数据 3

数据 4

数据 5

数据 6

数据 7

16 位

单声道

0x0001

0x0000

0x0005

0x0003

0x0009

0x0007

0x000d

0x000b

0x0002

0x0000

0x0006

0x0004

0x000a

0x0008

0x000e

0x000c

立体声

任意

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

备注

ESP32 上的接收有些复杂。首先,当数据位宽为 8 位或 24 位时,接收的数据仍将以 2 个字节或 4 个字节对齐,这意味着有效数据被放在每两个字节的高 8 位和每四个字节的高 24 位。例如,当线路上的数据是 8 位宽度的 0x5A 时,接收的数据将是 0x5A00;当数据是 0x00 005A 时,则收到 0x0000 5A00。其次,在 8 位宽和 16 位宽单声道传输中,缓冲区内每两个数据会进行一次数据翻转,因此可能需要手动将顺序回转,以获取正确的数据顺序。

#include "driver/i2s_std.h"
#include "driver/gpio.h"

i2s_chan_handle_t rx_handle;
/* 通过辅助宏获取默认的通道配置
 * 这个辅助宏在 'i2s_common.h' 中定义,由所有 I2S 通信模式共享
 * 它可以帮助指定 I2S 角色和端口 ID */
i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_AUTO, I2S_ROLE_MASTER);
/* 分配新的 TX 通道并获取该通道的句柄 */
i2s_new_channel(&chan_cfg, NULL, &rx_handle);

/* 进行配置,可以通过宏生成声道配置和时钟配置
 * 这两个辅助宏在 'i2s_std.h' 中定义,只能用于 STD 模式
 * 它们可以帮助初始化或更新声道和时钟配置 */
i2s_std_config_t std_cfg = {
    .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(48000),
    .slot_cfg = I2S_STD_MSB_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_32BIT, I2S_SLOT_MODE_STEREO),
    .gpio_cfg = {
        .mclk = I2S_GPIO_UNUSED,
        .bclk = GPIO_NUM_4,
        .ws = GPIO_NUM_5,
        .dout = I2S_GPIO_UNUSED,
        .din = GPIO_NUM_19,
        .invert_flags = {
            .mclk_inv = false,
            .bclk_inv = false,
            .ws_inv = false,
        },
    },
};
/* 初始化通道 */
i2s_channel_init_std_mode(rx_handle, &std_cfg);

/* 在读取数据之前,先启动 RX 通道 */
i2s_channel_enable(rx_handle);
i2s_channel_read(rx_handle, desc_buf, bytes_to_read, bytes_read, ticks_to_wait);

/* 删除通道之前必须先禁用通道 */
i2s_channel_disable(rx_handle);
/* 如果不再需要句柄,删除该句柄以释放通道资源 */
i2s_del_channel(rx_handle);

PDM TX 模式的应用

针对 TX 通道的 PDM 模式,声道配置的辅助宏为:

时钟配置的辅助宏为:

PDM TX API 的相关信息,可参考 PDM 模式。更多细节请参阅 esp_driver_i2s/include/driver/i2s_pdm.h

PDM 数据位宽固定为 16 位。如果 int16_t 写缓冲区中的数据如下:

数据 0

数据 1

数据 2

数据 3

数据 4

数据 5

数据 6

数据 7

...

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

...

下表展示了不同 i2s_pdm_tx_slot_config_t::slot_modei2s_pdm_tx_slot_config_t::slot_mask 设置下线路上的真实数据。为方便理解,已将线路上的数据格式由 PDM 转为 PCM。

声道模式

声道掩码

单声道

0x0001

0x0000

0x0002

0x0000

0x0003

0x0000

0x0004

0x0000

0x0000

0x0001

0x0000

0x0002

0x0000

0x0003

0x0000

0x0004

左右

0x0001

0x0001

0x0002

0x0002

0x0003

0x0003

0x0004

0x0004

立体声

0x0001

0x0001

0x0003

0x0003

0x0005

0x0005

0x0007

0x0007

0x0002

0x0002

0x0004

0x0004

0x0006

0x0006

0x0008

0x0008

左右

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

#include "driver/i2s_pdm.h"
#include "driver/gpio.h"

/* 分配 I2S TX 通道 */
i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_0, I2S_ROLE_MASTER);
i2s_new_channel(&chan_cfg, &tx_handle, NULL);

/* 初始化通道为 PDM TX 模式 */
i2s_pdm_tx_config_t pdm_tx_cfg = {
    .clk_cfg = I2S_PDM_TX_CLK_DEFAULT_CONFIG(36000),
    .slot_cfg = I2S_PDM_TX_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO),
    .gpio_cfg = {
        .clk = GPIO_NUM_5,
        .dout = GPIO_NUM_18,
        .invert_flags = {
            .clk_inv = false,
        },
    },
};
i2s_channel_init_pdm_tx_mode(tx_handle, &pdm_tx_cfg);

...

PDM RX 模式的应用

针对 RX 通道的 PDM 模式,声道配置的辅助宏为:

时钟配置的辅助宏为:

PDM RX API 的相关信息,可参考 PDM 模式。更多细节请参阅 esp_driver_i2s/include/driver/i2s_pdm.h

PDM 数据位宽固定为 16 位。如果线路上的数据如下所示。为方便理解,已将线路上的数据格式由 PDM 转为 PCM。

...

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

...

下表展示了不同 i2s_pdm_rx_slot_config_t::slot_modei2s_pdm_rx_slot_config_t::slot_mask 设置下 'int16_t' 缓冲区接收的数据。

声道模式

声道掩码

数据 0

数据 1

数据 2

数据 3

数据 4

数据 5

数据 6

数据 7

单声道

0x0001

0x0003

0x0005

0x0007

0x0009

0x000b

0x000d

0x000f

0x0002

0x0004

0x0006

0x0008

0x000a

0x000c

0x000e

0x0010

立体声

左右

0x0001

0x0002

0x0003

0x0004

0x0005

0x0006

0x0007

0x0008

#include "driver/i2s_pdm.h"
#include "driver/gpio.h"

i2s_chan_handle_t rx_handle;

/* 分配 I2S RX 通道 */
i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_0, I2S_ROLE_MASTER);
i2s_new_channel(&chan_cfg, NULL, &rx_handle);

/* 初始化通道为 PDM RX 模式 */
i2s_pdm_rx_config_t pdm_rx_cfg = {
    .clk_cfg = I2S_PDM_RX_CLK_DEFAULT_CONFIG(36000),
    .slot_cfg = I2S_PDM_RX_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO),
    .gpio_cfg = {
        .clk = GPIO_NUM_5,
        .din = GPIO_NUM_19,
        .invert_flags = {
            .clk_inv = false,
        },
    },
};
i2s_channel_init_pdm_rx_mode(rx_handle, &pdm_rx_cfg);

...

全双工

全双工模式可以在 I2S 端口中同时注册 TX 和 RX 通道,同时通道共享 BCLK 和 WS 信号。目前,STD 和 TDM 通信模式支持以下方式的全双工通信,但不支持 PDM 全双工模式,因为 PDM 模式下 TX 和 RX 通道的时钟不同。

请注意,一个句柄只能代表一个通道,因此仍然需要对 TX 和 RX 通道逐个进行声道和时钟配置。

以下示例展示了如何分配两个全双工通道:

#include "driver/i2s_std.h"
#include "driver/gpio.h"

i2s_chan_handle_t tx_handle;
i2s_chan_handle_t rx_handle;

/* 分配两个 I2S 通道 */
i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_AUTO, I2S_ROLE_MASTER);
/* 同时分配给 TX 和 RX 通道,使其进入全双工模式。 */
i2s_new_channel(&chan_cfg, &tx_handle, &rx_handle);

/* 配置两个通道,因为在全双工模式下,TX 和 RX 通道必须相同。 */
i2s_std_config_t std_cfg = {
    .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(32000),
    .slot_cfg = I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_STEREO),
    .gpio_cfg = {
        .mclk = I2S_GPIO_UNUSED,
        .bclk = GPIO_NUM_4,
        .ws = GPIO_NUM_5,
        .dout = GPIO_NUM_18,
        .din = GPIO_NUM_19,
        .invert_flags = {
            .mclk_inv = false,
            .bclk_inv = false,
            .ws_inv = false,
        },
    },
};
i2s_channel_init_std_mode(tx_handle, &std_cfg);
i2s_channel_init_std_mode(rx_handle, &std_cfg);

i2s_channel_enable(tx_handle);
i2s_channel_enable(rx_handle);

...

单工模式

在单工模式下分配通道句柄,应该为每个通道调用 i2s_new_channel()。在 ESP32 上,TX/RX 通道的时钟和 GPIO 管脚不是相互独立的,因此在单工模式下,TX 和 RX 通道不能共存于同一个 I2S 端口中。

#include "driver/i2s_std.h"
#include "driver/gpio.h"

i2s_chan_handle_t tx_handle;
i2s_chan_handle_t rx_handle;

i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_AUTO, I2S_ROLE_MASTER);
i2s_new_channel(&chan_cfg, &tx_handle, NULL);
i2s_std_config_t std_tx_cfg = {
    .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(48000),
    .slot_cfg = I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_STEREO),
    .gpio_cfg = {
        .mclk = GPIO_NUM_0,
        .bclk = GPIO_NUM_4,
        .ws = GPIO_NUM_5,
        .dout = GPIO_NUM_18,
        .din = I2S_GPIO_UNUSED,
        .invert_flags = {
            .mclk_inv = false,
            .bclk_inv = false,
            .ws_inv = false,
        },
    },
};
/* 初始化通道 */
i2s_channel_init_std_mode(tx_handle, &std_tx_cfg);
i2s_channel_enable(tx_handle);

/* 如果没有找到其他可用的 I2S 设备,RX 通道将被注册在另一个 I2S 上
 * 并返回 ESP_ERR_NOT_FOUND */
i2s_new_channel(&chan_cfg, NULL, &rx_handle);
i2s_std_config_t std_rx_cfg = {
    .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(16000),
    .slot_cfg = I2S_STD_MSB_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_32BIT, I2S_SLOT_MODE_STEREO),
    .gpio_cfg = {
        .mclk = I2S_GPIO_UNUSED,
        .bclk = GPIO_NUM_6,
        .ws = GPIO_NUM_7,
        .dout = I2S_GPIO_UNUSED,
        .din = GPIO_NUM_19,
        .invert_flags = {
            .mclk_inv = false,
            .bclk_inv = false,
            .ws_inv = false,
        },
    },
};
i2s_channel_init_std_mode(rx_handle, &std_rx_cfg);
i2s_channel_enable(rx_handle);

应用注意事项

防止数据丢失

对于需要高频采样率的应用,数据的巨大吞吐量可能会导致数据丢失。用户可以通过注册 ISR 回调函数来接收事件队列中的数据丢失事件:

static IRAM_ATTR bool i2s_rx_queue_overflow_callback(i2s_chan_handle_t handle, i2s_event_data_t *event, void *user_ctx)
{
    // 处理 RX 队列溢出事件 ...
    return false;
}

i2s_event_callbacks_t cbs = {
    .on_recv = NULL,
    .on_recv_q_ovf = i2s_rx_queue_overflow_callback,
    .on_sent = NULL,
    .on_send_q_ovf = NULL,
};
TEST_ESP_OK(i2s_channel_register_event_callback(rx_handle, &cbs, NULL));

请按照以下步骤操作,以防止数据丢失:

  1. 确定中断间隔。通常来说,当发生数据丢失时,为减少中断次数,中断间隔应该越久越好。因此,在保证 DMA 缓冲区大小不超过最大值 4092 的前提下,应使 dma_frame_num 尽可能大。具体转换关系如下:

    interrupt_interval(unit: sec) = dma_frame_num / sample_rate
    dma_buffer_size = dma_frame_num * slot_num * data_bit_width / 8 <= 4092
    
  2. 确定 dma_desc_num 的值。dma_desc_numi2s_channel_read 轮询周期的最大时间决定,所有接收到的数据都应该存储在两个 i2s_channel_read 之间。这个周期可以通过计时器或输出 GPIO 信号来计算。具体转换关系如下:

    dma_desc_num > polling_cycle / interrupt_interval
    
  3. 确定接收缓冲区大小。在 i2s_channel_read 中提供的接收缓冲区应当能够容纳所有 DMA 缓冲区中的数据,这意味着它应该大于所有 DMA 缓冲区的总大小:

    recv_buffer_size > dma_desc_num * dma_buffer_size
    

例如,如果某个 I2S 应用的已知值包括:

sample_rate = 144000 Hz
data_bit_width = 32 bits
slot_num = 2
polling_cycle = 10 ms

那么可以按照以下公式计算出参数 dma_frame_numdma_desc_numrecv_buf_size:

dma_frame_num * slot_num * data_bit_width / 8 = dma_buffer_size <= 4092
dma_frame_num <= 511
interrupt_interval = dma_frame_num / sample_rate = 511 / 144000 = 0.003549 s = 3.549 ms
dma_desc_num > polling_cycle / interrupt_interval = cell(10 / 3.549) = cell(2.818) = 3
recv_buffer_size > dma_desc_num * dma_buffer_size = 3 * 4092 = 12276 bytes

API 参考

标准模式

Header File

  • components/esp_driver_i2s/include/driver/i2s_std.h

  • This header file can be included with:

    #include "driver/i2s_std.h"
    
  • This header file is a part of the API provided by the esp_driver_i2s component. To declare that your component depends on esp_driver_i2s, add the following to your CMakeLists.txt:

    REQUIRES esp_driver_i2s
    

    or

    PRIV_REQUIRES esp_driver_i2s
    

Functions

esp_err_t i2s_channel_init_std_mode(i2s_chan_handle_t handle, const i2s_std_config_t *std_cfg)

Initialize I2S channel to standard mode.

备注

Only allowed to be called when the channel state is REGISTERED, (i.e., channel has been allocated, but not initialized) and the state will be updated to READY if initialization success, otherwise the state will return to REGISTERED.

参数
  • handle -- [in] I2S channel handler

  • std_cfg -- [in] Configurations for standard mode, including clock, slot and GPIO The clock configuration can be generated by the helper macro I2S_STD_CLK_DEFAULT_CONFIG The slot configuration can be generated by the helper macro I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG, I2S_STD_PCM_SLOT_DEFAULT_CONFIG or I2S_STD_MSB_SLOT_DEFAULT_CONFIG

返回

  • ESP_OK Initialize successfully

  • ESP_ERR_NO_MEM No memory for storing the channel information

  • ESP_ERR_INVALID_ARG NULL pointer or invalid configuration

  • ESP_ERR_INVALID_STATE This channel is not registered

esp_err_t i2s_channel_reconfig_std_clock(i2s_chan_handle_t handle, const i2s_std_clk_config_t *clk_cfg)

Reconfigure the I2S clock for standard mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to standard mode, i.e., i2s_channel_init_std_mode has been called before reconfiguring

参数
  • handle -- [in] I2S channel handler

  • clk_cfg -- [in] Standard mode clock configuration, can be generated by I2S_STD_CLK_DEFAULT_CONFIG

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not standard mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

esp_err_t i2s_channel_reconfig_std_slot(i2s_chan_handle_t handle, const i2s_std_slot_config_t *slot_cfg)

Reconfigure the I2S slot for standard mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to standard mode, i.e., i2s_channel_init_std_mode has been called before reconfiguring

参数
  • handle -- [in] I2S channel handler

  • slot_cfg -- [in] Standard mode slot configuration, can be generated by I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG, I2S_STD_PCM_SLOT_DEFAULT_CONFIG and I2S_STD_MSB_SLOT_DEFAULT_CONFIG.

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_NO_MEM No memory for DMA buffer

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not standard mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

esp_err_t i2s_channel_reconfig_std_gpio(i2s_chan_handle_t handle, const i2s_std_gpio_config_t *gpio_cfg)

Reconfigure the I2S GPIO for standard mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to standard mode, i.e., i2s_channel_init_std_mode has been called before reconfiguring

参数
  • handle -- [in] I2S channel handler

  • gpio_cfg -- [in] Standard mode GPIO configuration, specified by user

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not standard mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

Structures

struct i2s_std_slot_config_t

I2S slot configuration for standard mode.

Public Members

i2s_data_bit_width_t data_bit_width

I2S sample data bit width (valid data bits per sample)

i2s_slot_bit_width_t slot_bit_width

I2S slot bit width (total bits per slot)

i2s_slot_mode_t slot_mode

Set mono or stereo mode with I2S_SLOT_MODE_MONO or I2S_SLOT_MODE_STEREO In TX direction, mono means the written buffer contains only one slot data and stereo means the written buffer contains both left and right data

i2s_std_slot_mask_t slot_mask

Select the left, right or both slot

uint32_t ws_width

WS signal width (i.e. the number of BCLK ticks that WS signal is high)

bool ws_pol

WS signal polarity, set true to enable high lever first

bool bit_shift

Set to enable bit shift in Philips mode

bool msb_right

Set to place right channel data at the MSB in the FIFO

struct i2s_std_clk_config_t

I2S clock configuration for standard mode.

Public Members

uint32_t sample_rate_hz

I2S sample rate

i2s_clock_src_t clk_src

Choose clock source, see soc_periph_i2s_clk_src_t for the supported clock sources. selected I2S_CLK_SRC_EXTERNAL (if supports) to enable the external source clock input via MCLK pin,

i2s_mclk_multiple_t mclk_multiple

The multiple of MCLK to the sample rate Default is 256 in the helper macro, it can satisfy most of cases, but please set this field a multiple of 3 (like 384) when using 24-bit data width, otherwise the sample rate might be inaccurate

struct i2s_std_gpio_config_t

I2S standard mode GPIO pins configuration.

Public Members

gpio_num_t mclk

MCK pin, output by default, input if the clock source is selected to I2S_CLK_SRC_EXTERNAL

gpio_num_t bclk

BCK pin, input in slave role, output in master role

gpio_num_t ws

WS pin, input in slave role, output in master role

gpio_num_t dout

DATA pin, output

gpio_num_t din

DATA pin, input

uint32_t mclk_inv

Set 1 to invert the MCLK input/output

uint32_t bclk_inv

Set 1 to invert the BCLK input/output

uint32_t ws_inv

Set 1 to invert the WS input/output

struct i2s_std_gpio_config_t::[anonymous] invert_flags

GPIO pin invert flags

struct i2s_std_config_t

I2S standard mode major configuration that including clock/slot/GPIO configuration.

Public Members

i2s_std_clk_config_t clk_cfg

Standard mode clock configuration, can be generated by macro I2S_STD_CLK_DEFAULT_CONFIG

i2s_std_slot_config_t slot_cfg

Standard mode slot configuration, can be generated by macros I2S_STD_[mode]_SLOT_DEFAULT_CONFIG, [mode] can be replaced with PHILIPS/MSB/PCM

i2s_std_gpio_config_t gpio_cfg

Standard mode GPIO configuration, specified by user

Macros

I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG(bits_per_sample, mono_or_stereo)

Philips format in 2 slots.

This file is specified for I2S standard communication mode Features:

  • Philips/MSB/PCM are supported in standard mode

  • Fixed to 2 slots

参数
  • bits_per_sample -- I2S data bit width

  • mono_or_stereo -- I2S_SLOT_MODE_MONO or I2S_SLOT_MODE_STEREO

I2S_STD_PCM_SLOT_DEFAULT_CONFIG(bits_per_sample, mono_or_stereo)

PCM(short) format in 2 slots.

备注

PCM(long) is same as Philips in 2 slots

参数
  • bits_per_sample -- I2S data bit width

  • mono_or_stereo -- I2S_SLOT_MODE_MONO or I2S_SLOT_MODE_STEREO

I2S_STD_MSB_SLOT_DEFAULT_CONFIG(bits_per_sample, mono_or_stereo)

MSB format in 2 slots.

参数
  • bits_per_sample -- I2S data bit width

  • mono_or_stereo -- I2S_SLOT_MODE_MONO or I2S_SLOT_MODE_STEREO

I2S_STD_CLK_DEFAULT_CONFIG(rate)

I2S default standard clock configuration.

备注

Please set the mclk_multiple to I2S_MCLK_MULTIPLE_384 while using 24 bits data width Otherwise the sample rate might be imprecise since the BCLK division is not a integer

参数
  • rate -- sample rate

PDM 模式

Header File

  • components/esp_driver_i2s/include/driver/i2s_pdm.h

  • This header file can be included with:

    #include "driver/i2s_pdm.h"
    
  • This header file is a part of the API provided by the esp_driver_i2s component. To declare that your component depends on esp_driver_i2s, add the following to your CMakeLists.txt:

    REQUIRES esp_driver_i2s
    

    or

    PRIV_REQUIRES esp_driver_i2s
    

Functions

esp_err_t i2s_channel_init_pdm_rx_mode(i2s_chan_handle_t handle, const i2s_pdm_rx_config_t *pdm_rx_cfg)

Initialize I2S channel to PDM RX mode.

备注

Only allowed to be called when the channel state is REGISTERED, (i.e., channel has been allocated, but not initialized) and the state will be updated to READY if initialization success, otherwise the state will return to REGISTERED.

参数
  • handle -- [in] I2S RX channel handler

  • pdm_rx_cfg -- [in] Configurations for PDM RX mode, including clock, slot and GPIO The clock configuration can be generated by the helper macro I2S_PDM_RX_CLK_DEFAULT_CONFIG The slot configuration can be generated by the helper macro I2S_PDM_RX_SLOT_DEFAULT_CONFIG

返回

  • ESP_OK Initialize successfully

  • ESP_ERR_NO_MEM No memory for storing the channel information

  • ESP_ERR_INVALID_ARG NULL pointer or invalid configuration

  • ESP_ERR_INVALID_STATE This channel is not registered

esp_err_t i2s_channel_reconfig_pdm_rx_clock(i2s_chan_handle_t handle, const i2s_pdm_rx_clk_config_t *clk_cfg)

Reconfigure the I2S clock for PDM RX mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to PDM RX mode, i.e., i2s_channel_init_pdm_rx_mode has been called before reconfiguring

参数
  • handle -- [in] I2S RX channel handler

  • clk_cfg -- [in] PDM RX mode clock configuration, can be generated by I2S_PDM_RX_CLK_DEFAULT_CONFIG

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not PDM mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

esp_err_t i2s_channel_reconfig_pdm_rx_slot(i2s_chan_handle_t handle, const i2s_pdm_rx_slot_config_t *slot_cfg)

Reconfigure the I2S slot for PDM RX mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to PDM RX mode, i.e., i2s_channel_init_pdm_rx_mode has been called before reconfiguring

参数
  • handle -- [in] I2S RX channel handler

  • slot_cfg -- [in] PDM RX mode slot configuration, can be generated by I2S_PDM_RX_SLOT_DEFAULT_CONFIG

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_NO_MEM No memory for DMA buffer

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not PDM mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

esp_err_t i2s_channel_reconfig_pdm_rx_gpio(i2s_chan_handle_t handle, const i2s_pdm_rx_gpio_config_t *gpio_cfg)

Reconfigure the I2S GPIO for PDM RX mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to PDM RX mode, i.e., i2s_channel_init_pdm_rx_mode has been called before reconfiguring

参数
  • handle -- [in] I2S RX channel handler

  • gpio_cfg -- [in] PDM RX mode GPIO configuration, specified by user

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not PDM mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

esp_err_t i2s_channel_init_pdm_tx_mode(i2s_chan_handle_t handle, const i2s_pdm_tx_config_t *pdm_tx_cfg)

Initialize I2S channel to PDM TX mode.

备注

Only allowed to be called when the channel state is REGISTERED, (i.e., channel has been allocated, but not initialized) and the state will be updated to READY if initialization success, otherwise the state will return to REGISTERED.

参数
  • handle -- [in] I2S TX channel handler

  • pdm_tx_cfg -- [in] Configurations for PDM TX mode, including clock, slot and GPIO The clock configuration can be generated by the helper macro I2S_PDM_TX_CLK_DEFAULT_CONFIG The slot configuration can be generated by the helper macro I2S_PDM_TX_SLOT_DEFAULT_CONFIG

返回

  • ESP_OK Initialize successfully

  • ESP_ERR_NO_MEM No memory for storing the channel information

  • ESP_ERR_INVALID_ARG NULL pointer or invalid configuration

  • ESP_ERR_INVALID_STATE This channel is not registered

esp_err_t i2s_channel_reconfig_pdm_tx_clock(i2s_chan_handle_t handle, const i2s_pdm_tx_clk_config_t *clk_cfg)

Reconfigure the I2S clock for PDM TX mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to PDM TX mode, i.e., i2s_channel_init_pdm_tx_mode has been called before reconfiguring

参数
  • handle -- [in] I2S TX channel handler

  • clk_cfg -- [in] PDM TX mode clock configuration, can be generated by I2S_PDM_TX_CLK_DEFAULT_CONFIG

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not PDM mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

esp_err_t i2s_channel_reconfig_pdm_tx_slot(i2s_chan_handle_t handle, const i2s_pdm_tx_slot_config_t *slot_cfg)

Reconfigure the I2S slot for PDM TX mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to PDM TX mode, i.e., i2s_channel_init_pdm_tx_mode has been called before reconfiguring

参数
  • handle -- [in] I2S TX channel handler

  • slot_cfg -- [in] PDM TX mode slot configuration, can be generated by I2S_PDM_TX_SLOT_DEFAULT_CONFIG

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_NO_MEM No memory for DMA buffer

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not PDM mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

esp_err_t i2s_channel_reconfig_pdm_tx_gpio(i2s_chan_handle_t handle, const i2s_pdm_tx_gpio_config_t *gpio_cfg)

Reconfigure the I2S GPIO for PDM TX mode.

备注

Only allowed to be called when the channel state is READY, i.e., channel has been initialized, but not started this function won't change the state. i2s_channel_disable should be called before calling this function if I2S has started.

备注

The input channel handle has to be initialized to PDM TX mode, i.e., i2s_channel_init_pdm_tx_mode has been called before reconfiguring

参数
  • handle -- [in] I2S TX channel handler

  • gpio_cfg -- [in] PDM TX mode GPIO configuration, specified by user

返回

  • ESP_OK Set clock successfully

  • ESP_ERR_INVALID_ARG NULL pointer, invalid configuration or not PDM mode

  • ESP_ERR_INVALID_STATE This channel is not initialized or not stopped

Structures

struct i2s_pdm_rx_slot_config_t

I2S slot configuration for PDM RX mode.

Public Members

i2s_data_bit_width_t data_bit_width

I2S sample data bit width (valid data bits per sample), only support 16 bits for PDM mode

i2s_slot_bit_width_t slot_bit_width

I2S slot bit width (total bits per slot) , only support 16 bits for PDM mode

i2s_slot_mode_t slot_mode

Set mono or stereo mode with I2S_SLOT_MODE_MONO or I2S_SLOT_MODE_STEREO

i2s_pdm_slot_mask_t slot_mask

Choose the slots to activate

struct i2s_pdm_rx_clk_config_t

I2S clock configuration for PDM RX mode.

Public Members

uint32_t sample_rate_hz

I2S sample rate

i2s_clock_src_t clk_src

Choose clock source

i2s_mclk_multiple_t mclk_multiple

The multiple of MCLK to the sample rate

i2s_pdm_dsr_t dn_sample_mode

Down-sampling rate mode

uint32_t bclk_div

The division from MCLK to BCLK. The typical and minimum value is I2S_PDM_RX_BCLK_DIV_MIN. It will be set to I2S_PDM_RX_BCLK_DIV_MIN by default if it is smaller than I2S_PDM_RX_BCLK_DIV_MIN

struct i2s_pdm_rx_gpio_config_t

I2S PDM TX mode GPIO pins configuration.

Public Members

gpio_num_t clk

PDM clk pin, output

gpio_num_t din

DATA pin 0, input

gpio_num_t dins[(1U)]

DATA pins, input, only take effect when corresponding I2S_PDM_RX_LINEx_SLOT_xxx is enabled in i2s_pdm_rx_slot_config_t::slot_mask

uint32_t clk_inv

Set 1 to invert the clk output

struct i2s_pdm_rx_gpio_config_t::[anonymous] invert_flags

GPIO pin invert flags

struct i2s_pdm_rx_config_t

I2S PDM RX mode major configuration that including clock/slot/GPIO configuration.

Public Members

i2s_pdm_rx_clk_config_t clk_cfg

PDM RX clock configurations, can be generated by macro I2S_PDM_RX_CLK_DEFAULT_CONFIG

i2s_pdm_rx_slot_config_t slot_cfg

PDM RX slot configurations, can be generated by macro I2S_PDM_RX_SLOT_DEFAULT_CONFIG

i2s_pdm_rx_gpio_config_t gpio_cfg

PDM RX slot configurations, specified by user

struct i2s_pdm_tx_slot_config_t

I2S slot configuration for PDM TX mode.

Public Members

i2s_data_bit_width_t data_bit_width

I2S sample data bit width (valid data bits per sample), only support 16 bits for PDM mode

i2s_slot_bit_width_t slot_bit_width

I2S slot bit width (total bits per slot), only support 16 bits for PDM mode

i2s_slot_mode_t slot_mode

Set mono or stereo mode with I2S_SLOT_MODE_MONO or I2S_SLOT_MODE_STEREO For PDM TX mode, mono means the data buffer only contains one slot data, Stereo means the data buffer contains two slots data

i2s_pdm_slot_mask_t slot_mask

Slot mask to choose left or right slot

uint32_t sd_prescale

Sigma-delta filter prescale

i2s_pdm_sig_scale_t sd_scale

Sigma-delta filter scaling value

i2s_pdm_sig_scale_t hp_scale

High pass filter scaling value

i2s_pdm_sig_scale_t lp_scale

Low pass filter scaling value

i2s_pdm_sig_scale_t sinc_scale

Sinc filter scaling value

struct i2s_pdm_tx_clk_config_t

I2S clock configuration for PDM TX mode.

Public Members

uint32_t sample_rate_hz

I2S sample rate, not suggest to exceed 48000 Hz, otherwise more glitches and noise may appear

i2s_clock_src_t clk_src

Choose clock source

i2s_mclk_multiple_t mclk_multiple

The multiple of MCLK to the sample rate

uint32_t up_sample_fp

Up-sampling param fp

uint32_t up_sample_fs

Up-sampling param fs, not allowed to be greater than 480

uint32_t bclk_div

The division from MCLK to BCLK. The minimum value is I2S_PDM_TX_BCLK_DIV_MIN. It will be set to I2S_PDM_TX_BCLK_DIV_MIN by default if it is smaller than I2S_PDM_TX_BCLK_DIV_MIN

struct i2s_pdm_tx_gpio_config_t

I2S PDM TX mode GPIO pins configuration.

Public Members

gpio_num_t clk

PDM clk pin, output

gpio_num_t dout

DATA pin, output

uint32_t clk_inv

Set 1 to invert the clk output

struct i2s_pdm_tx_gpio_config_t::[anonymous] invert_flags

GPIO pin invert flags

struct i2s_pdm_tx_config_t

I2S PDM TX mode major configuration that including clock/slot/GPIO configuration.

Public Members

i2s_pdm_tx_clk_config_t clk_cfg

PDM TX clock configurations, can be generated by macro I2S_PDM_TX_CLK_DEFAULT_CONFIG

i2s_pdm_tx_slot_config_t slot_cfg

PDM TX slot configurations, can be generated by macro I2S_PDM_TX_SLOT_DEFAULT_CONFIG

i2s_pdm_tx_gpio_config_t gpio_cfg

PDM TX GPIO configurations, specified by user

Macros

I2S_PDM_RX_SLOT_DEFAULT_CONFIG(bits_per_sample, mono_or_stereo)

PDM format in 2 slots(RX)

This file is specified for I2S PDM communication mode Features:

  • Only support PDM TX/RX mode

  • Fixed to 2 slots

  • Data bit width only support 16 bits

参数
  • bits_per_sample -- I2S data bit width, only support 16 bits for PDM mode

  • mono_or_stereo -- I2S_SLOT_MODE_MONO or I2S_SLOT_MODE_STEREO

I2S_PDM_RX_CLK_DEFAULT_CONFIG(rate)

I2S default PDM RX clock configuration.

参数
  • rate -- sample rate

I2S_PDM_TX_SLOT_DEFAULT_CONFIG(bits_per_sample, mono_or_stereo)

PDM style in 2 slots(TX) for codec line mode.

参数
  • bits_per_sample -- I2S data bit width, only support 16 bits for PDM mode

  • mono_or_stereo -- I2S_SLOT_MODE_MONO or I2S_SLOT_MODE_STEREO

I2S_PDM_TX_CLK_DEFAULT_CONFIG(rate)

I2S default PDM TX clock configuration for codec line mode.

备注

TX PDM can only be set to the following two up-sampling rate configurations: 1: fp = 960, fs = sample_rate_hz / 100, in this case, Fpdm = 128*48000 2: fp = 960, fs = 480, in this case, Fpdm = 128*Fpcm = 128*sample_rate_hz If the PDM receiver do not care the PDM serial clock, it's recommended set Fpdm = 128*48000. Otherwise, the second configuration should be adopted.

参数
  • rate -- sample rate (not suggest to exceed 48000 Hz, otherwise more glitches and noise may appear)

I2S_PDM_TX_CLK_DAC_DEFAULT_CONFIG(rate)

I2S default PDM TX clock configuration for DAC line mode.

备注

TX PDM can only be set to the following two up-sampling rate configurations: 1: fp = 960, fs = sample_rate_hz / 100, in this case, Fpdm = 128*48000 2: fp = 960, fs = 480, in this case, Fpdm = 128*Fpcm = 128*sample_rate_hz If the PDM receiver do not care the PDM serial clock, it's recommended set Fpdm = 128*48000. Otherwise, the second configuration should be adopted.

备注

The noise might be different with different configurations, this macro provides a set of configurations that have relatively high SNR (Signal Noise Ratio), you can also adjust them to fit your case.

参数
  • rate -- sample rate (not suggest to exceed 48000 Hz, otherwise more glitches and noise may appear)

I2S 驱动

Header File

  • components/esp_driver_i2s/include/driver/i2s_common.h

  • This header file can be included with:

    #include "driver/i2s_common.h"
    
  • This header file is a part of the API provided by the esp_driver_i2s component. To declare that your component depends on esp_driver_i2s, add the following to your CMakeLists.txt:

    REQUIRES esp_driver_i2s
    

    or

    PRIV_REQUIRES esp_driver_i2s
    

Functions

esp_err_t i2s_new_channel(const i2s_chan_config_t *chan_cfg, i2s_chan_handle_t *ret_tx_handle, i2s_chan_handle_t *ret_rx_handle)

Allocate new I2S channel(s)

备注

The new created I2S channel handle will be REGISTERED state after it is allocated successfully.

备注

When the port id in channel configuration is I2S_NUM_AUTO, driver will allocate I2S port automatically on one of the I2S controller, otherwise driver will try to allocate the new channel on the selected port.

备注

If both tx_handle and rx_handle are not NULL, it means this I2S controller will work at full-duplex mode, the RX and TX channels will be allocated on a same I2S port in this case. Note that some configurations of TX/RX channel are shared on ESP32 and ESP32S2, so please make sure they are working at same condition and under same status(start/stop). Currently, full-duplex mode can't guarantee TX/RX channels write/read synchronously, they can only share the clock signals for now.

备注

If tx_handle OR rx_handle is NULL, it means this I2S controller will work at simplex mode. For ESP32 and ESP32S2, the whole I2S controller (i.e. both RX and TX channel) will be occupied, even if only one of RX or TX channel is registered. For the other targets, another channel on this controller will still available.

参数
  • chan_cfg -- [in] I2S controller channel configurations

  • ret_tx_handle -- [out] I2S channel handler used for managing the sending channel(optional)

  • ret_rx_handle -- [out] I2S channel handler used for managing the receiving channel(optional)

返回

  • ESP_OK Allocate new channel(s) success

  • ESP_ERR_NOT_SUPPORTED The communication mode is not supported on the current chip

  • ESP_ERR_INVALID_ARG NULL pointer or illegal parameter in i2s_chan_config_t

  • ESP_ERR_NOT_FOUND No available I2S channel found

esp_err_t i2s_del_channel(i2s_chan_handle_t handle)

Delete the I2S channel.

备注

Only allowed to be called when the I2S channel is at REGISTERED or READY state (i.e., it should stop before deleting it).

备注

Resource will be free automatically if all channels in one port are deleted

参数

handle -- [in] I2S channel handler

  • ESP_OK Delete successfully

  • ESP_ERR_INVALID_ARG NULL pointer

esp_err_t i2s_channel_get_info(i2s_chan_handle_t handle, i2s_chan_info_t *chan_info)

Get I2S channel information.

参数
  • handle -- [in] I2S channel handler

  • chan_info -- [out] I2S channel basic information

返回

  • ESP_OK Get I2S channel information success

  • ESP_ERR_NOT_FOUND The input handle doesn't match any registered I2S channels, it may not an I2S channel handle or not available any more

  • ESP_ERR_INVALID_ARG The input handle or chan_info pointer is NULL

esp_err_t i2s_channel_enable(i2s_chan_handle_t handle)

Enable the I2S channel.

备注

Only allowed to be called when the channel state is READY, (i.e., channel has been initialized, but not started) the channel will enter RUNNING state once it is enabled successfully.

备注

Enable the channel can start the I2S communication on hardware. It will start outputting BCLK and WS signal. For MCLK signal, it will start to output when initialization is finished

参数

handle -- [in] I2S channel handler

  • ESP_OK Start successfully

  • ESP_ERR_INVALID_ARG NULL pointer

  • ESP_ERR_INVALID_STATE This channel has not initialized or already started

esp_err_t i2s_channel_disable(i2s_chan_handle_t handle)

Disable the I2S channel.

备注

Only allowed to be called when the channel state is RUNNING, (i.e., channel has been started) the channel will enter READY state once it is disabled successfully.

备注

Disable the channel can stop the I2S communication on hardware. It will stop BCLK and WS signal but not MCLK signal

参数

handle -- [in] I2S channel handler

返回

  • ESP_OK Stop successfully

  • ESP_ERR_INVALID_ARG NULL pointer

  • ESP_ERR_INVALID_STATE This channel has not stated

esp_err_t i2s_channel_preload_data(i2s_chan_handle_t tx_handle, const void *src, size_t size, size_t *bytes_loaded)

Preload the data into TX DMA buffer.

备注

Only allowed to be called when the channel state is READY, (i.e., channel has been initialized, but not started)

备注

As the initial DMA buffer has no data inside, it will transmit the empty buffer after enabled the channel, this function is used to preload the data into the DMA buffer, so that the valid data can be transmitted immediately after the channel is enabled.

备注

This function can be called multiple times before enabling the channel, the buffer that loaded later will be concatenated behind the former loaded buffer. But when all the DMA buffers have been loaded, no more data can be preload then, please check the bytes_loaded parameter to see how many bytes are loaded successfully, when the bytes_loaded is smaller than the size, it means the DMA buffers are full.

参数
  • tx_handle -- [in] I2S TX channel handler

  • src -- [in] The pointer of the source buffer to be loaded

  • size -- [in] The source buffer size

  • bytes_loaded -- [out] The bytes that successfully been loaded into the TX DMA buffer

返回

  • ESP_OK Load data successful

  • ESP_ERR_INVALID_ARG NULL pointer or not TX direction

  • ESP_ERR_INVALID_STATE This channel has not stated

esp_err_t i2s_channel_write(i2s_chan_handle_t handle, const void *src, size_t size, size_t *bytes_written, uint32_t timeout_ms)

I2S write data.

备注

Only allowed to be called when the channel state is RUNNING, (i.e., TX channel has been started and is not writing now) but the RUNNING only stands for the software state, it doesn't mean there is no the signal transporting on line.

参数
  • handle -- [in] I2S channel handler

  • src -- [in] The pointer of sent data buffer

  • size -- [in] Max data buffer length

  • bytes_written -- [out] Byte number that actually be sent, can be NULL if not needed

  • timeout_ms -- [in] Max block time

返回

  • ESP_OK Write successfully

  • ESP_ERR_INVALID_ARG NULL pointer or this handle is not TX handle

  • ESP_ERR_TIMEOUT Writing timeout, no writing event received from ISR within ticks_to_wait

  • ESP_ERR_INVALID_STATE I2S is not ready to write

esp_err_t i2s_channel_read(i2s_chan_handle_t handle, void *dest, size_t size, size_t *bytes_read, uint32_t timeout_ms)

I2S read data.

备注

Only allowed to be called when the channel state is RUNNING but the RUNNING only stands for the software state, it doesn't mean there is no the signal transporting on line.

参数
  • handle -- [in] I2S channel handler

  • dest -- [in] The pointer of receiving data buffer

  • size -- [in] Max data buffer length

  • bytes_read -- [out] Byte number that actually be read, can be NULL if not needed

  • timeout_ms -- [in] Max block time

返回

  • ESP_OK Read successfully

  • ESP_ERR_INVALID_ARG NULL pointer or this handle is not RX handle

  • ESP_ERR_TIMEOUT Reading timeout, no reading event received from ISR within ticks_to_wait

  • ESP_ERR_INVALID_STATE I2S is not ready to read

esp_err_t i2s_channel_register_event_callback(i2s_chan_handle_t handle, const i2s_event_callbacks_t *callbacks, void *user_data)

Set event callbacks for I2S channel.

备注

Only allowed to be called when the channel state is REGISTERED / READY, (i.e., before channel starts)

备注

User can deregister a previously registered callback by calling this function and setting the callback member in the callbacks structure to NULL.

备注

When CONFIG_I2S_ISR_IRAM_SAFE is enabled, the callback itself and functions called by it should be placed in IRAM. The variables used in the function should be in the SRAM as well. The user_data should also reside in SRAM or internal RAM as well.

参数
  • handle -- [in] I2S channel handler

  • callbacks -- [in] Group of callback functions

  • user_data -- [in] User data, which will be passed to callback functions directly

返回

  • ESP_OK Set event callbacks successfully

  • ESP_ERR_INVALID_ARG Set event callbacks failed because of invalid argument

  • ESP_ERR_INVALID_STATE Set event callbacks failed because the current channel state is not REGISTERED or READY

Structures

struct i2s_event_callbacks_t

Group of I2S callbacks.

备注

The callbacks are all running under ISR environment

备注

When CONFIG_I2S_ISR_IRAM_SAFE is enabled, the callback itself and functions called by it should be placed in IRAM. The variables used in the function should be in the SRAM as well.

Public Members

i2s_isr_callback_t on_recv

Callback of data received event, only for RX channel The event data includes DMA buffer address and size that just finished receiving data

i2s_isr_callback_t on_recv_q_ovf

Callback of receiving queue overflowed event, only for RX channel The event data includes buffer size that has been overwritten

i2s_isr_callback_t on_sent

Callback of data sent event, only for TX channel The event data includes DMA buffer address and size that just finished sending data

i2s_isr_callback_t on_send_q_ovf

Callback of sending queue overflowed event, only for TX channel The event data includes buffer size that has been overwritten

struct i2s_chan_config_t

I2S controller channel configuration.

Public Members

i2s_port_t id

I2S port id

i2s_role_t role

I2S role, I2S_ROLE_MASTER or I2S_ROLE_SLAVE

uint32_t dma_desc_num

I2S DMA buffer number, it is also the number of DMA descriptor

uint32_t dma_frame_num

I2S frame number in one DMA buffer. One frame means one-time sample data in all slots, it should be the multiple of 3 when the data bit width is 24.

bool auto_clear

Alias of auto_clear_after_cb

bool auto_clear_after_cb

Set to auto clear DMA TX buffer after on_sent callback, I2S will always send zero automatically if no data to send. So that user can assign the data to the DMA buffers directly in the callback, and the data won't be cleared after quit the callback.

bool auto_clear_before_cb

Set to auto clear DMA TX buffer before on_sent callback, I2S will always send zero automatically if no data to send So that user can access data in the callback that just finished to send.

int intr_priority

I2S interrupt priority, range [0, 7], if set to 0, the driver will try to allocate an interrupt with a relative low priority (1,2,3)

struct i2s_chan_info_t

I2S channel information.

Public Members

i2s_port_t id

I2S port id

i2s_role_t role

I2S role, I2S_ROLE_MASTER or I2S_ROLE_SLAVE

i2s_dir_t dir

I2S channel direction

i2s_comm_mode_t mode

I2S channel communication mode

i2s_chan_handle_t pair_chan

I2S pair channel handle in duplex mode, always NULL in simplex mode

uint32_t total_dma_buf_size

Total size of all the allocated DMA buffers

  • 0 if the channel has not been initialized

  • non-zero if the channel has been initialized

Macros

I2S_CHANNEL_DEFAULT_CONFIG(i2s_num, i2s_role)

get default I2S property

I2S_GPIO_UNUSED

Used in i2s_gpio_config_t for signals which are not used

I2S 类型

Header File

  • components/esp_driver_i2s/include/driver/i2s_types.h

  • This header file can be included with:

    #include "driver/i2s_types.h"
    
  • This header file is a part of the API provided by the esp_driver_i2s component. To declare that your component depends on esp_driver_i2s, add the following to your CMakeLists.txt:

    REQUIRES esp_driver_i2s
    

    or

    PRIV_REQUIRES esp_driver_i2s
    

Structures

struct i2s_event_data_t

Event structure used in I2S event queue.

Public Members

void *data

(Deprecated) The secondary pointer of DMA buffer that just finished sending or receiving for on_recv and on_sent callback NULL for on_recv_q_ovf and on_send_q_ovf callback

void *dma_buf

The first level pointer of DMA buffer that just finished sending or receiving for on_recv and on_sent callback NULL for on_recv_q_ovf and on_send_q_ovf callback

size_t size

The buffer size of DMA buffer when success to send or receive, also the buffer size that dropped when queue overflow. It is related to the dma_frame_num and data_bit_width, typically it is fixed when data_bit_width is not changed.

Type Definitions

typedef struct i2s_channel_obj_t *i2s_chan_handle_t

I2S channel object handle, the control unit of the I2S driver

typedef bool (*i2s_isr_callback_t)(i2s_chan_handle_t handle, i2s_event_data_t *event, void *user_ctx)

I2S event callback.

Param handle

[in] I2S channel handle, created from i2s_new_channel()

Param event

[in] I2S event data

Param user_ctx

[in] User registered context, passed from i2s_channel_register_event_callback()

Return

Whether a high priority task has been waken up by this callback function

Enumerations

enum i2s_port_t

I2S controller port number, the max port number is (SOC_I2S_NUM -1).

Values:

enumerator I2S_NUM_0

I2S controller port 0

enumerator I2S_NUM_1

I2S controller port 1

enumerator I2S_NUM_AUTO

Select whichever port is available

enum i2s_comm_mode_t

I2S controller communication mode.

Values:

enumerator I2S_COMM_MODE_STD

I2S controller using standard communication mode, support Philips/MSB/PCM format

enumerator I2S_COMM_MODE_PDM

I2S controller using PDM communication mode, support PDM output or input

enumerator I2S_COMM_MODE_NONE

Unspecified I2S controller mode

enum i2s_mclk_multiple_t

The multiple of MCLK to sample rate.

备注

MCLK is the minimum resolution of the I2S clock. Increasing mclk multiple can reduce the clock jitter of BCLK and WS, which is also useful for the codec that don't require MCLK but have strict requirement to BCLK. For the 24-bit slot width, please choose a multiple that can be divided by 3 (i.e. 24-bit compatible).

Values:

enumerator I2S_MCLK_MULTIPLE_128

MCLK = sample_rate * 128

enumerator I2S_MCLK_MULTIPLE_192

MCLK = sample_rate * 192 (24-bit compatible)

enumerator I2S_MCLK_MULTIPLE_256

MCLK = sample_rate * 256

enumerator I2S_MCLK_MULTIPLE_384

MCLK = sample_rate * 384 (24-bit compatible)

enumerator I2S_MCLK_MULTIPLE_512

MCLK = sample_rate * 512

enumerator I2S_MCLK_MULTIPLE_576

MCLK = sample_rate * 576 (24-bit compatible)

enumerator I2S_MCLK_MULTIPLE_768

MCLK = sample_rate * 768 (24-bit compatible)

enumerator I2S_MCLK_MULTIPLE_1024

MCLK = sample_rate * 1024

enumerator I2S_MCLK_MULTIPLE_1152

MCLK = sample_rate * 1152 (24-bit compatible)

Header File

Type Definitions

typedef soc_periph_i2s_clk_src_t i2s_clock_src_t

I2S clock source

Enumerations

enum i2s_slot_mode_t

I2S channel slot mode.

Values:

enumerator I2S_SLOT_MODE_MONO

I2S channel slot format mono, transmit same data in all slots for tx mode, only receive the data in the first slots for rx mode.

enumerator I2S_SLOT_MODE_STEREO

I2S channel slot format stereo, transmit different data in different slots for tx mode, receive the data in all slots for rx mode.

enum i2s_dir_t

I2S channel direction.

Values:

enumerator I2S_DIR_RX

I2S channel direction RX

enumerator I2S_DIR_TX

I2S channel direction TX

enum i2s_role_t

I2S controller role.

Values:

enumerator I2S_ROLE_MASTER

I2S controller master role, bclk and ws signal will be set to output

enumerator I2S_ROLE_SLAVE

I2S controller slave role, bclk and ws signal will be set to input

enum i2s_data_bit_width_t

Available data bit width in one slot.

Values:

enumerator I2S_DATA_BIT_WIDTH_8BIT

I2S channel data bit-width: 8

enumerator I2S_DATA_BIT_WIDTH_16BIT

I2S channel data bit-width: 16

enumerator I2S_DATA_BIT_WIDTH_24BIT

I2S channel data bit-width: 24

enumerator I2S_DATA_BIT_WIDTH_32BIT

I2S channel data bit-width: 32

enum i2s_slot_bit_width_t

Total slot bit width in one slot.

Values:

enumerator I2S_SLOT_BIT_WIDTH_AUTO

I2S channel slot bit-width equals to data bit-width

enumerator I2S_SLOT_BIT_WIDTH_8BIT

I2S channel slot bit-width: 8

enumerator I2S_SLOT_BIT_WIDTH_16BIT

I2S channel slot bit-width: 16

enumerator I2S_SLOT_BIT_WIDTH_24BIT

I2S channel slot bit-width: 24

enumerator I2S_SLOT_BIT_WIDTH_32BIT

I2S channel slot bit-width: 32

enum i2s_pdm_dsr_t

I2S PDM RX down-sampling mode.

Values:

enumerator I2S_PDM_DSR_8S

downsampling number is 8 for PDM RX mode

enumerator I2S_PDM_DSR_16S

downsampling number is 16 for PDM RX mode

enumerator I2S_PDM_DSR_MAX
enum i2s_pdm_sig_scale_t

pdm tx singnal scaling mode

Values:

enumerator I2S_PDM_SIG_SCALING_DIV_2

I2S TX PDM signal scaling: /2

enumerator I2S_PDM_SIG_SCALING_MUL_1

I2S TX PDM signal scaling: x1

enumerator I2S_PDM_SIG_SCALING_MUL_2

I2S TX PDM signal scaling: x2

enumerator I2S_PDM_SIG_SCALING_MUL_4

I2S TX PDM signal scaling: x4

enum i2s_std_slot_mask_t

I2S slot select in standard mode.

备注

It has different meanings in tx/rx/mono/stereo mode, and it may have differen behaviors on different targets For the details, please refer to the I2S API reference

Values:

enumerator I2S_STD_SLOT_LEFT

I2S transmits or receives left slot

enumerator I2S_STD_SLOT_RIGHT

I2S transmits or receives right slot

enumerator I2S_STD_SLOT_BOTH

I2S transmits or receives both left and right slot

enum i2s_pdm_slot_mask_t

I2S slot select in PDM mode.

Values:

enumerator I2S_PDM_SLOT_RIGHT

I2S PDM only transmits or receives the PDM device whose 'select' pin is pulled up

enumerator I2S_PDM_SLOT_LEFT

I2S PDM only transmits or receives the PDM device whose 'select' pin is pulled down

enumerator I2S_PDM_SLOT_BOTH

I2S PDM transmits or receives both two slots