mirror of
https://github.com/espressif/esp-idf.git
synced 2026-08-18 06:35:35 +03:00
feat(i2s): support to select PDM data format
This commit is contained in:
laokaiyao
@@ -115,19 +115,23 @@ I2S Communication Mode
|
||||
Overview of All Modes
|
||||
^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
========= ======== ======== ======== ======== ======== ==========
|
||||
Target Standard PDM TX PDM RX TDM ADC/DAC LCD/Camera
|
||||
========= ======== ======== ======== ======== ======== ==========
|
||||
ESP32 I2S 0/1 I2S 0 I2S 0 none I2S 0 I2S 0
|
||||
ESP32-S2 I2S 0 none none none none I2S 0
|
||||
ESP32-C3 I2S 0 I2S 0 none I2S 0 none none
|
||||
ESP32-C6 I2S 0 I2S 0 none I2S 0 none none
|
||||
ESP32-S3 I2S 0/1 I2S 0 I2S 0 I2S 0/1 none none
|
||||
ESP32-H2 I2S 0 I2S 0 none I2S 0 none none
|
||||
ESP32-P4 I2S 0~2 I2S 0 I2S 0 I2S 0~2 none none
|
||||
ESP32-C5 I2S 0 I2S 0 I2S 0 I2S 0 none none
|
||||
ESP32-C61 I2S 0 I2S 0 I2S 0 I2S 0 none none
|
||||
========= ======== ======== ======== ======== ======== ==========
|
||||
========= ======== ============ ============ ========= ======== ======== ==========
|
||||
Target Standard PCM-to-PDM PDM-to-PCM PDM TDM ADC/DAC LCD/Camera
|
||||
========= ======== ============ ============ ========= ======== ======== ==========
|
||||
ESP32 I2S 0/1 I2S 0 I2S 0 I2S 0/1 none I2S 0 I2S 0
|
||||
ESP32-S2 I2S 0 none none none none none I2S 0
|
||||
ESP32-C3 I2S 0 I2S 0 none I2S 0 I2S 0 none none
|
||||
ESP32-C6 I2S 0 I2S 0 none I2S 0 I2S 0 none none
|
||||
ESP32-S3 I2S 0/1 I2S 0 I2S 0 I2S 0/1 I2S 0/1 none none
|
||||
ESP32-H2 I2S 0 I2S 0 none I2S 0 I2S 0 none none
|
||||
ESP32-P4 I2S 0~2 I2S 0 I2S 0 I2S 0~2 I2S 0~2 none none
|
||||
ESP32-C5 I2S 0 I2S 0 I2S 0 I2S 0 I2S 0 none none
|
||||
ESP32-C61 I2S 0 I2S 0 I2S 0 I2S 0 I2S 0 none none
|
||||
========= ======== ============ ============ ========= ======== ======== ==========
|
||||
|
||||
.. note::
|
||||
|
||||
If you are using PDM mode, note that not all I2S ports support conversion between raw PDM and PCM formats, because these ports do not have PCM-to-PDM data format converter in TX direction, or PDM-to-PCM data format converter in RX direction. Ports without the converter can only read/write raw PDM data. To read/write PCM format data on these ports, you may need an extra software filter for PDM-to-PCM conversion.
|
||||
|
||||
Standard Mode
|
||||
^^^^^^^^^^^^^
|
||||
@@ -147,28 +151,76 @@ In standard mode, there are always two sound channels, i.e., the left and right
|
||||
.. wavedrom:: /../_static/diagrams/i2s/std_pcm.json
|
||||
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM_TX
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM
|
||||
|
||||
PDM Mode (TX)
|
||||
^^^^^^^^^^^^^
|
||||
PDM Mode
|
||||
^^^^^^^^
|
||||
|
||||
PDM (Pulse-density Modulation) mode for the TX channel can convert PCM data into PDM format which always has left and right slots. PDM TX is only supported on I2S0 and it only supports 16-bit width sample data. It needs at least a CLK pin for clock signal and a DOUT pin for data signal (i.e., the WS and SD signal in the following figure; the BCK signal is an internal bit sampling clock, which is not needed between PDM devices). This mode allows users to configure the up-sampling parameters :cpp:member:`i2s_pdm_tx_clk_config_t::up_sample_fp` and :cpp:member:`i2s_pdm_tx_clk_config_t::up_sample_fs`. The up-sampling rate can be calculated by ``up_sample_rate = i2s_pdm_tx_clk_config_t::up_sample_fp / i2s_pdm_tx_clk_config_t::up_sample_fs``. There are two up-sampling modes in PDM TX:
|
||||
|
||||
- **Fixed Clock Frequency**: In this mode, the up-sampling rate changes according to the sample rate. Setting ``fp = 960`` and ``fs = sample_rate / 100``, then the clock frequency (Fpdm) on CLK pin will be fixed to ``128 * 48 KHz = 6.144 MHz``. Note that this frequency is not equal to the sample rate (Fpcm).
|
||||
- **Fixed Up-sampling Rate**: In this mode, the up-sampling rate is fixed to 2. Setting ``fp = 960`` and ``fs = 480``, then the clock frequency (Fpdm) on CLK pin will be ``128 * sample_rate``.
|
||||
PDM (Pulse-density Modulation) digitalizes the analog signal by oversampling with 1-bit resolution. It represents the analog signal by the pulse density, the higher the pulse density, the larger the corresponding analog quantity. The PDM timing diagram is shown as follow:
|
||||
|
||||
.. wavedrom:: /../_static/diagrams/i2s/pdm.json
|
||||
|
||||
The PDM format data can be transferred into PCM format by the following steps:
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM_RX
|
||||
1. Low-pass filtering: To restore the analog wave. It is usually a FIR filter;
|
||||
2. Down-sampling: To reduce the PDM sample rate to the expected PCM sample rate. Normally we decimate one sample every specific number of samples;
|
||||
3. High-pass filtering: To remove the DC offset of the analog wave;
|
||||
4. Amplifying: To adjust the final gain of the converted PCM format data. It can be done by simply amplifying a coefficient.
|
||||
|
||||
PDM Mode (RX)
|
||||
^^^^^^^^^^^^^
|
||||
For I2S ports with a ``PCM-to-PDM`` converter, the hardware can convert PCM format data to PDM format when sending the data.
|
||||
For I2S ports with a ``PDM-to-PCM`` converter, the hardware can convert PDM format data to PCM format when receiving the data.
|
||||
If the hardware does not have the converters above, then the PDM mode can only read/write raw PDM format data. You need to realize a software filter to convert the raw PDM data into PCM format.
|
||||
|
||||
PDM (Pulse-density Modulation) mode for RX channel can receive PDM-format data and convert the data into PCM format. PDM RX is only supported on I2S0, and it only supports 16-bit width sample data. PDM RX needs at least a CLK pin for clock signal and a DIN pin for data signal. This mode allows users to configure the down-sampling parameter :cpp:member:`i2s_pdm_rx_clk_config_t::dn_sample_mode`. There are two down-sampling modes in PDM RX:
|
||||
.. note::
|
||||
|
||||
- :cpp:enumerator:`i2s_pdm_dsr_t::I2S_PDM_DSR_8S`: In this mode, the clock frequency (Fpdm) on the WS pin is ``sample_rate (Fpcm) * 64``.
|
||||
- :cpp:enumerator:`i2s_pdm_dsr_t::I2S_PDM_DSR_16S`: In this mode, the clock frequency (Fpdm) on the WS pin is ``sample_rate (Fpcm) * 128``.
|
||||
In PDM mode, regardless of whether you are using raw PDM or PCM format, the data unit width is always 16 bits. For example, if you are sending data in raw PDM format, the data in the buffer is supposed to be arranged as follows: CH0 0x1234, CH1 0x5678, CH0 0x9abc, CH1 0xdef0. Same in the RX direction.
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM_TX
|
||||
|
||||
PDM TX Mode in Raw PDM Format
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
To use the PDM TX mode in raw PDM format, set :cpp:member:`i2s_pdm_tx_slot_config_t::data_fmt` to :cpp:enumerator:`i2s_pdm_data_fmt_t::I2S_PDM_DATA_FMT_RAW`. Be cautious when setting :cpp:member:`i2s_pdm_tx_clk_config_t::sample_rate_hz`, as the PDM sample rate is normally in the MHz range, typically between 1.024 MHz and 6.144 MHz. Adjust it according to your needs.
|
||||
|
||||
As for the slot configuration of raw PDM format, you can use the helper macros like :c:macro:`I2S_PDM_TX_SLOT_RAW_FMT_DEFAULT_CONFIG` or :c:macro:`I2S_PDM_TX_SLOT_RAW_FMT_DAC_DEFAULT_CONFIG`.
|
||||
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PCM2PDM
|
||||
|
||||
PDM TX Mode in PCM Format (with PCM-to-PDM Converter)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
{IDF_TARGET_NAME} supports PCM-to-PDM converter on ``I2S0``. To send PCM format data in the PDM TX mode, you need to set :cpp:member:`i2s_pdm_tx_slot_config_t::data_fmt` to :cpp:enumerator:`i2s_pdm_data_fmt_t::I2S_PDM_DATA_FMT_PCM`. And then please take care when setting the :cpp:member:`i2s_pdm_tx_clk_config_t::sample_rate_hz`, the PCM sample rate is normally below 100KHz, typically, it ranges from 16KHz to 48KHz, you can set it according to your needs.
|
||||
|
||||
And the up-sampling parameters can be set for the PCM-to-PDM converter, i.e., :cpp:member:`i2s_pdm_tx_clk_config_t::up_sample_fp` and :cpp:member:`i2s_pdm_tx_clk_config_t::up_sample_fs`. The up-sampling rate can be calculated by ``up_sample_rate = i2s_pdm_tx_clk_config_t::up_sample_fp / i2s_pdm_tx_clk_config_t::up_sample_fs``. There are two up-sampling modes for PCM-to-PDM converter. The relation of the PDM clock on CLK pin and the PCM sample rate that set in the driver are shown as follow:
|
||||
|
||||
- **Fixed Clock Frequency**: In this mode, the up-sampling rate changes according to the sample rate. Setting ``fp = 960`` and ``fs = (PCM)sample_rate / 100``, then the PDM clock frequency on the CLK pin will be fixed to ``128 * 48 KHz = 6.144 MHz``.
|
||||
- **Fixed Up-sampling Rate**: In this mode, the up-sampling rate is fixed to 2. Setting ``fp = 960`` and ``fs = 480``, then the PDM clock frequency on CLK pin will be ``128 * (PCM)sample_rate``.
|
||||
|
||||
As for the slot configuration of PCM format, you can use the helper macros like :c:macro:`I2S_PDM_TX_SLOT_PCM_FMT_DEFAULT_CONFIG` or :c:macro:`I2S_PDM_TX_SLOT_PCM_FMT_DAC_DEFAULT_CONFIG`.
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM_RX
|
||||
|
||||
PDM RX Mode in Raw PDM Format
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
To use the PDM RX mode in raw PDM format, you need to set :cpp:member:`i2s_pdm_rx_slot_config_t::data_fmt` to :cpp:enumerator:`i2s_pdm_data_fmt_t::I2S_PDM_DATA_FMT_RAW`. And then please take care when setting the :cpp:member:`i2s_pdm_rx_clk_config_t::sample_rate_hz`, the PDM sample rate is normally several MHz, typically, it ranges from 1.024MHz to 6.144MHz, you can set it according to your needs.
|
||||
|
||||
As for the slot configuration of raw PDM format, you can use the helper macro :c:macro:`I2S_PDM_RX_SLOT_RAW_FMT_DEFAULT_CONFIG`.
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM2PCM
|
||||
|
||||
PDM RX Mode in PCM Format (with PDM-to-PCM Converter)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
{IDF_TARGET_NAME} supports PDM-to-PCM converter on ``I2S0``. To receive PCM format data in the PDM RX mode, you need to set :cpp:member:`i2s_pdm_rx_slot_config_t::data_fmt` to :cpp:enumerator:`i2s_pdm_data_fmt_t::I2S_PDM_DATA_FMT_PCM`. And then please take care when setting the :cpp:member:`i2s_pdm_rx_clk_config_t::sample_rate_hz`, the PCM sample rate is normally below 100KHz, typically, it ranges from 16KHz to 48KHz, you can set it according to your needs.
|
||||
|
||||
The down-sampling parameter can be set to the PDM-to-PCM converter, which is :cpp:member:`i2s_pdm_rx_clk_config_t::dn_sample_mode`. There are two down-sampling modes for PDM-to-PCM converter, the relation of the PDM clock on CLK pin and the PCM sample rate that set in the driver are shown as follow:
|
||||
|
||||
- :cpp:enumerator:`i2s_pdm_dsr_t::I2S_PDM_DSR_8S`: In this mode, the PDM clock frequency on the CLK pin is ``(PCM) sample_rate * 64``.
|
||||
- :cpp:enumerator:`i2s_pdm_dsr_t::I2S_PDM_DSR_16S`: In this mode, the PDM clock frequency on the CLK pin is ``(PCM) sample_rate * 128``.
|
||||
|
||||
As for the slot configuration of PCM format, you can use the helper macro like :c:macro:`I2S_PDM_RX_SLOT_PCM_FMT_DEFAULT_CONFIG`
|
||||
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_TDM
|
||||
@@ -666,9 +718,13 @@ Here is the table of the data received in the buffer with different :cpp:member:
|
||||
- :example:`peripherals/i2s/i2s_recorder` demonstrates how to record audio from a digital MEMS microphone using the I2S peripheral in PDM data format and save it to an SD card in ``.wav`` file format on {IDF_TARGET_NAME} development boards.
|
||||
- :example:`peripherals/i2s/i2s_basic/i2s_pdm` demonstrates how to use the PDM RX mode on {IDF_TARGET_NAME}, including the necessary hardware setup and configuration.
|
||||
|
||||
For PDM mode in RX channel, the slot configuration helper macro is:
|
||||
For PDM mode in RX channel, the slot configuration helper macro are:
|
||||
|
||||
- :c:macro:`I2S_PDM_RX_SLOT_DEFAULT_CONFIG`
|
||||
- :c:macro:`I2S_PDM_RX_SLOT_RAW_FMT_DEFAULT_CONFIG` It provides some default configurations for receiving the raw PDM format data.
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM2PCM
|
||||
|
||||
- :c:macro:`I2S_PDM_RX_SLOT_PCM_FMT_DEFAULT_CONFIG` It provides some default configurations for receiving the converted PCM format data.
|
||||
|
||||
The clock configuration helper macro is:
|
||||
|
||||
@@ -730,7 +786,9 @@ Here is the table of the data received in the buffer with different :cpp:member:
|
||||
/* Init the channel into PDM RX mode */
|
||||
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),
|
||||
// If PDM-to-PCM converter is not supported, please use raw PDM format
|
||||
// .slot_cfg = I2S_PDM_RX_SLOT_RAW_FMT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO),
|
||||
.slot_cfg = I2S_PDM_RX_SLOT_PCM_FMT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO),
|
||||
.gpio_cfg = {
|
||||
.clk = GPIO_NUM_5,
|
||||
.din = GPIO_NUM_19,
|
||||
|
||||
@@ -115,19 +115,23 @@ 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 无 I2S 0 I2S 0
|
||||
ESP32-S2 I2S 0 无 无 无 无 I2S 0
|
||||
ESP32-C3 I2S 0 I2S 0 无 I2S 0 无 无
|
||||
ESP32-C6 I2S 0 I2S 0 无 I2S 0 无 无
|
||||
ESP32-S3 I2S 0/1 I2S 0 I2S 0 I2S 0/1 无 无
|
||||
ESP32-H2 I2S 0 I2S 0 无 I2S 0 无 无
|
||||
ESP32-P4 I2S 0~2 I2S 0 I2S 0 I2S 0~2 无 无
|
||||
ESP32-C5 I2S 0 I2S 0 I2S 0 I2S 0 无 无
|
||||
ESP32-C61 I2S 0 I2S 0 I2S 0 I2S 0 无 无
|
||||
========= ======== ======== ======== ======== ======== ==========
|
||||
========= ======== ========== ========== =========== ========== ======== ===========
|
||||
芯片 I2S 标准 PCM-to-PDM PDM-to-PCM PDM TDM ADC/DAC LCD/摄像头
|
||||
========= ======== ========== ========== =========== ========== ======== ===========
|
||||
ESP32 I2S 0/1 I2S 0 I2S 0 I2S 0/1 无 I2S 0 I2S 0
|
||||
ESP32-S2 I2S 0 无 无 无 无 无 I2S 0
|
||||
ESP32-C3 I2S 0 I2S 0 无 I2S 0 I2S 0 无 无
|
||||
ESP32-C6 I2S 0 I2S 0 无 I2S 0 I2S 0 无 无
|
||||
ESP32-S3 I2S 0/1 I2S 0 I2S 0 I2S 0/1 I2S 0/1 无 无
|
||||
ESP32-H2 I2S 0 I2S 0 无 I2S 0 I2S 0 无 无
|
||||
ESP32-P4 I2S 0~2 I2S 0 I2S 0 I2S 0~2 I2S 0~2 无 无
|
||||
ESP32-C5 I2S 0 I2S 0 I2S 0 I2S 0 I2S 0 无 无
|
||||
ESP32-C61 I2S 0 I2S 0 I2S 0 I2S 0 I2S 0 无 无
|
||||
========= ======== ========== ========== =========== ========== ======== ===========
|
||||
|
||||
.. note::
|
||||
|
||||
如需使用 PDM 模式，请注意不是所有 I2S 端口都支持原始 PDM 格式与 PCM 格式之间的转换，因为有些端口在 TX 方向上没有 PCM-to-PDM 数据格式转换器，或在 RX 方向上没有 PDM-to-PCM 数据格式转换器。因此，这些没有硬件格式转换器的端口只能读写原始 PDM 格式的数据。如果需要在这些端口上处理 PCM 格式的数据，则需额外采用一个软件滤波器来实现 PDM 格式和 PCM 格式之间的转换。
|
||||
|
||||
标准模式
|
||||
^^^^^^^^
|
||||
@@ -147,28 +151,76 @@ ESP32-C61 I2S 0 I2S 0 I2S 0 I2S 0 无 无
|
||||
.. wavedrom:: /../_static/diagrams/i2s/std_pcm.json
|
||||
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM_TX
|
||||
|
||||
PDM 模式 (TX)
|
||||
^^^^^^^^^^^^^
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM
|
||||
|
||||
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 :cpp:member:`i2s_pdm_tx_clk_config_t::up_sample_fp` 和 :cpp:member:`i2s_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：
|
||||
PDM 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 = 960``、 ``fs = 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 = 960``、 ``fs = 480``，则 CLK 管脚上的时钟频率 (Fpdm) 将为 ``128 * sample_rate``。
|
||||
PDM（Pulse-density Modulation，脉冲密度调制）通过采样的方式将模拟信号数字化为 1 位精度的数字信号。它以脉冲密度的方式呈现模拟信号的大小，即密度越高，对应的模拟信号值越大。PDM 时序图如下所示：
|
||||
|
||||
.. wavedrom:: /../_static/diagrams/i2s/pdm.json
|
||||
|
||||
PDM 格式的数据通常可以经过以下几个步骤转换为 PCM 格式：
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM_RX
|
||||
1. 低通滤波：用于还原模拟信号波形。一般采用 FIR 滤波器；
|
||||
2. 下采样：用于将 PDM 的过采样率降低到期望的 PCM 采样率。下采样可以用简单的抽值法实现；
|
||||
3. 高通滤波：用于去除信号的直流部分；
|
||||
4. 放大：用于调整转换后的 PCM 数据的増益。一般由转换后的 PCM 信号乘以一个系数得到最终 PCM 信号。
|
||||
|
||||
PDM 模式 (RX)
|
||||
^^^^^^^^^^^^^
|
||||
对于具有 ``PCM-to-PDM`` 格式转换器的 I2S 端口，可以在发送数据的时候，将 PCM 数据转换为 PDM 格式发送。
|
||||
对于具有 ``PDM-to-PCM`` 格式转换器的 I2S 端口，可以再接收数据的时候，将收到的 PDM 格式的数据转换为 PCM 格式。
|
||||
若硬件不具备上述的格式转换器，则 PDM 模式只能收发原始的 PDM 格式数据。需要在软件上实现 PDM-to-PCM 的转换逻辑以此得到常用的 PCM 格式数据。
|
||||
|
||||
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 :cpp:member:`i2s_pdm_rx_clk_config_t::dn_sample_mode`。在 PDM RX 中有以下两种下采样模式：
|
||||
.. note::
|
||||
|
||||
- :cpp:enumerator:`i2s_pdm_dsr_t::I2S_PDM_DSR_8S`：在这种模式下，WS 管脚的时钟频率 (Fpdm) 将为 ``sample_rate (Fpcm) * 64``。
|
||||
- :cpp:enumerator:`i2s_pdm_dsr_t::I2S_PDM_DSR_16S`： 在这种模式下，WS 管脚的时钟频率 (Fpdm) 将为 ``sample_rate (Fpcm) * 128``。
|
||||
无论原始 PDM 格式还是 PCM 格式，PDM 模式下的一个数据单元总是 16 比特的位宽。例如，用原始 PDM 格式发送数据，那么您数组中的数据应该像这样排列：CH0 0x1234，CH1 0x5678，CH0 0x9abc，CH1 0xdef0。RX 方向同理。
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM_TX
|
||||
|
||||
PDM TX 模式原始 PDM 数据格式
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
要发送原始 PDM 格式的数据，您需要将 :cpp:member:`i2s_pdm_tx_slot_config_t::data_fmt` 设为 :cpp:enumerator:`i2s_pdm_data_fmt_t::I2S_PDM_DATA_FMT_RAW`。另外在设置 :cpp:member:`i2s_pdm_tx_clk_config_t::sample_rate_hz` 时请注意，PDM 的采样率通常在若干 MHz，典型值范围一般是 1.024MHz 到 6.144MHz 之间，您可以根据需求来设置。
|
||||
|
||||
而原始 PDM 数据格式下的声道配置，可以通过帮助宏 :c:macro:`I2S_PDM_TX_SLOT_RAW_FMT_DEFAULT_CONFIG` 或 ::c:macro:`I2S_PDM_TX_SLOT_RAW_FMT_DAC_DEFAULT_CONFIG` 来配置。
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PCM2PDM
|
||||
|
||||
PDM TX 模式 PCM 数据格式（采用 PCM-to-PDM 格式转换器）
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
{IDF_TARGET_NAME} 在 ``I2S0`` 上支持 PCM-to-PDM 格式转换器，您可以通过 :cpp:member:`i2s_pdm_tx_slot_config_t::data_fmt` 设为 :cpp:enumerator:`i2s_pdm_data_fmt_t::I2S_PDM_DATA_FMT_PCM` 来启用 PCM-to-PDM 格式转换器。启用后会将发送的 PCM 格式的数据转换为 PDM 格式发送。另外在设置 :cpp:member:`i2s_pdm_tx_clk_config_t::sample_rate_hz` 时请注意，PCM 的采样率通常低于 100 KHz，典型值的范围一般是 16KHz 到 48KHz 之间，您可以根据需求来设置。
|
||||
|
||||
另外 PCM-to-PDM 转换器可配置上采样参数 :cpp:member:`i2s_pdm_tx_clk_config_t::up_sample_fp` 和 :cpp:member:`i2s_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，输出的 PDM 采样频率和配置的 PCM 采样频率关系如下：
|
||||
|
||||
- **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 = 960``、 ``fs = (PCM)sample_rate / 100``，则 CLK 管脚上的输出的 PDM 时钟频率将固定为 ``128 * 48 KHz = 6.144 MHz``。
|
||||
- **固定上采样率模式**：在这种模式下，上采样率固定为 2。即设置 ``fp = 960``、 ``fs = 480``，则 CLK 管脚上的 PDM 的时钟频率将为 ``128 * sample_rate``。
|
||||
|
||||
而 PCM 数据格式下的声道配置，您可以通过帮助宏 :c:macro:`I2S_PDM_TX_SLOT_PCM_FMT_DEFAULT_CONFIG` 和 :c:macro:`I2S_PDM_TX_SLOT_PCM_FMT_DAC_DEFAULT_CONFIG` 来配置。
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM_RX
|
||||
|
||||
PDM RX 模式原始 PDM 数据格式
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
要接收原始 PDM 格式的数据，您需要将 :cpp:member:`i2s_pdm_rx_slot_config_t::data_fmt` 设为 :cpp:enumerator:`i2s_pdm_data_fmt_t::I2S_PDM_DATA_FMT_RAW`。另外在设置 :cpp:member:`i2s_pdm_rx_clk_config_t::sample_rate_hz` 时请注意，PDM 的采样率通常在若干 MHz，典型值范围一般是 1.024MHz 到 6.144MHz 之间，您可以根据需求来设置。
|
||||
|
||||
而原始 PDM 数据格式下的声道配置，可以通过帮助宏 :c:macro:`I2S_PDM_RX_SLOT_RAW_FMT_DEFAULT_CONFIG` 来配置。
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM2PCM
|
||||
|
||||
PDM RX 模式 PCM 数据格式（采用 PDM-to-PCM 格式转换器）
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
{IDF_TARGET_NAME} 在 ``I2S0`` 上支持 PDM-to-PCM 格式转换器，您可以通过 :cpp:member:`i2s_pdm_rx_slot_config_t::data_fmt` 设为 :cpp:enumerator:`i2s_pdm_data_fmt_t::I2S_PDM_DATA_FMT_PCM` 来启用 PDM-to-PCM 格式转换器。启用后会将接收到的 PDM 格式的数据转换为 PCM 格式。另外在设置 :cpp:member:`i2s_pdm_rx_clk_config_t::sample_rate_hz` 时请注意，PCM 的采样率通常低于 100 KHz，典型值的范围一般是 16KHz 到 48KHz 之间，您可以根据需求来设置。
|
||||
|
||||
另外 PDM-to-PCM 转换器可配置下采样参数 :cpp:member:`i2s_pdm_rx_clk_config_t::dn_sample_mode`。在 PDM RX 中有以下两种下采样模式，输出的 PDM 采样频率和配置的 PCM 采样频率关系如下：
|
||||
|
||||
- :cpp:enumerator:`i2s_pdm_dsr_t::I2S_PDM_DSR_8S`：在这种模式下，CLK 管脚的 PDM 时钟频率将为 ``(PCM) sample_rate * 64``。
|
||||
- :cpp:enumerator:`i2s_pdm_dsr_t::I2S_PDM_DSR_16S`： 在这种模式下，CLK 管脚的 PDM 时钟频率将为 ``(PCM) sample_rate * 128``。
|
||||
|
||||
而 PCM 数据格式下的声道配置，可以通过帮助宏 :c:macro:`I2S_PDM_RX_SLOT_PCM_FMT_DEFAULT_CONFIG` 来配置。
|
||||
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_TDM
|
||||
@@ -668,7 +720,11 @@ STD RX 模式
|
||||
|
||||
针对 RX 通道的 PDM 模式，声道配置的辅助宏为：
|
||||
|
||||
- :c:macro:`I2S_PDM_RX_SLOT_DEFAULT_CONFIG`
|
||||
- :c:macro:`I2S_PDM_RX_SLOT_RAW_FMT_DEFAULT_CONFIG` 该辅助宏为接收原始 PDM 数据格式提供了一些默认配置。
|
||||
|
||||
.. only:: SOC_I2S_SUPPORTS_PDM2PCM
|
||||
|
||||
- :c:macro:`I2S_PDM_RX_SLOT_PCM_FMT_DEFAULT_CONFIG` 该辅助宏为接收转换后的 PCM 数据格式提供了一些默认配置。
|
||||
|
||||
时钟配置的辅助宏为：
|
||||
|
||||
@@ -730,7 +786,9 @@ STD RX 模式
|
||||
/* 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),
|
||||
// 若不支持 PDM 转 PCM 格式转换器，请使用原始 PDM 格式
|
||||
// .slot_cfg = I2S_PDM_RX_SLOT_RAW_FMT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO),
|
||||
.slot_cfg = I2S_PDM_RX_SLOT_PCM_FMT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO),
|
||||
.gpio_cfg = {
|
||||
.clk = GPIO_NUM_5,
|
||||
.din = GPIO_NUM_19,
|
||||
|
||||
Reference in New Issue
Block a user