オーディオ¶

オーディオ ADC（PDM マイクとアナログマイク）と I2S。説明はヘッダーファイルのコメント（英語）から取っています。

hal_auadc.h¶

#include "hal_auadc.h"（ソースコード）

Audio ADC (AUADC) driver: analog or PDM microphone capture into a DMA ping-pong buffer, high-pass filter and gain control.

Capture is 16-bit mono PCM. Typical sequence: hal_auadc_amic_init() or hal_auadc_pdm_init(), optional gain and filter settings, hal_auadc_start(); the frame callback then runs every time one half of the ping-pong buffer is full. Stop with hal_auadc_stop() and release the DMA channel with hal_auadc_deinit().

The DMA writes one contiguous region of 2 x pcm_frame_size bytes that starts at pcm_frame_buf[0]: allocate it as one block and set pcm_frame_buf[1] to pcm_frame_buf[0] + pcm_frame_size bytes. On a cached system, invalidate the half named by the callback before reading it.

hal_auadc_real_rate¶

uint32_t hal_auadc_real_rate(uint32_t nominal_rate);

Get the actual capture rate for a nominal rate setting.

The figures are suitable for buffer sizing. An application that needs an exact time base should calibrate against a known reference signal.

戻り値：Actual rate in Hz: 7937 for 8000; 47625 for 32000 (this setting runs at three times the 16 kHz rate); 48000 for 48000 (not characterized); 15875 for 16000 and for any other value.

hal_auadc_amic_init¶

int hal_auadc_amic_init(hal_auadc_amic_cfg_t *cfg);

Initialize analog microphone capture.

Validates cfg, obtains a DMA channel, sets the input pins to analog mode, configures the audio ADC (nominal 16 kHz, analog gain 42 dB) and the DMA ping-pong transfer. Capture does not start until hal_auadc_start().

hal_auadc_pdm_init¶

int hal_auadc_pdm_init(hal_auadc_pdm_cfg_t *cfg);

Initialize PDM microphone capture.

Validates cfg, obtains a DMA channel, muxes the clock and data pins to the PDM function, configures the audio ADC at the requested rate and the DMA ping-pong transfer. Capture does not start until hal_auadc_start().

hal_auadc_start¶

int hal_auadc_start(void);

Start capture.

Arms the DMA ping-pong transfer from the start of pcm_frame_buf[0] and starts the audio ADC.

hal_auadc_stop¶

int hal_auadc_stop(void);

Stop capture.

Stops the DMA channel and the audio ADC and clears the ADC FIFO. The configuration is kept; hal_auadc_start() resumes capture from the first half.

hal_auadc_deinit¶

void hal_auadc_deinit(void);

Release the DMA channel obtained by hal_auadc_amic_init() or hal_auadc_pdm_init().

Call it after hal_auadc_stop() once capture is no longer needed; otherwise the DMA channel stays allocated. Also clears the frame callback. Does nothing if no init has been done.

hal_auadc_set_high_pass_filter¶

void hal_auadc_set_high_pass_filter(int k1, int k2);

Configure the first-order high-pass filter of the capture path.

Transfer function: H(z) = (1 - z^-1) / (1 - (1 - 2^-k1 - 2^-k2) z^-1). Larger coefficients give a lower corner frequency. The reset default is k1 = 8 with the k2 term disabled.

hal_auadc_set_analog_gain¶

void hal_auadc_set_analog_gain(int gain_db);

Set the analog (PGA) gain of the analog microphone input.

hal_auadc_amic_init() programs 42 dB; call this function after init to change it.

hal_auadc_set_digital_gain¶

void hal_auadc_set_digital_gain(float gain_db);

Set the digital gain of the capture path.

hal_auadc_get_analog_gain¶

int hal_auadc_get_analog_gain(void);

Get the current analog (PGA) gain.

戻り値：Gain in dB, 6 to 42.

hal_auadc_get_digital_gain¶

float hal_auadc_get_digital_gain(void);

Get the current digital gain.

戻り値：Gain in dB, in 0.5 dB steps.

無名列挙型¶

PDM channel selection for hal_auadc_pdm_cfg_t::pdm_ch.

hal_auadc_amic_cfg_t¶

Analog microphone configuration for hal_auadc_amic_init().

The analog input channels 0 to 7 are GPIO 4, 5, 6, 7, 10, 11, 12 and 13. Capture runs at the nominal 16 kHz setting (15875 Hz actual).

hal_auadc_pdm_cfg_t¶

PDM (digital) microphone configuration for hal_auadc_pdm_init().

The HAL does not validate the pin numbers. When GPIO 18 or 19 is used, the HAL first releases those pads from the 32 kHz crystal oscillator and selects the internal RC 32 kHz clock if the crystal was in use.

型定義¶

hal_i2s.h¶

#include "hal_i2s.h"（ソースコード）

I2S driver: master or slave operation, I2S, justified and DSP/PCM formats, DMA transfers.

Typical sequence: fill an i2s_device_t, hal_i2s_setConfig(), hal_i2s_init() with the DMA capability flags, attach DMA channels with I2S_CTRL_ATTACH_TX_DMA and I2S_CTRL_ATTACH_RX_DMA, then queue transfers with hal_i2s_write() and hal_i2s_read(). Pin multiplexing is not done by this driver. Fixed options (endianness, mono channel, clock inversion) come from i2s_config.h.

hal_i2s_setConfig¶

void hal_i2s_setConfig(i2s_device_t *dev);

Store an I2S configuration for the next hal_i2s_init().

Copies dev into the driver slot selected by i2s_device_t::id.

hal_i2s_write¶

int hal_i2s_write(int i2s_id, const void *buffer, uint32_t size);

Queue a DMA transmit transfer.

Reloads the attached TX DMA channel with size bytes from buffer and starts it; returns without waiting for completion.

hal_i2s_read¶

int hal_i2s_read(int i2s_id, void *buffer, uint32_t size);

Queue a DMA receive transfer.

Reloads the attached RX DMA channel to receive size bytes into buffer and starts it; returns without waiting for completion.

hal_i2s_control¶

int hal_i2s_control(int i2s_id, int cmd, void *args);

Control the I2S interface.

戻り値：The FIFO count for I2S_CTRL_GET_TX_FIFO and I2S_CTRL_GET_RX_FIFO; otherwise 0 on success, or -1 for an unknown command or (for I2S_CTRL_SET_SAMPL_FREQ) an invalid configured frame size.

hal_i2s_init¶

int hal_i2s_init(int i2s_id, uint16_t caps);

Initialize and enable an I2S interface with the configuration stored by hal_i2s_setConfig().

Programs the format, frame and sample sizes, channel count, bit clock (derived from the I2S peripheral clock and i2s_device_t::sampl_freq_hz) and FIFO, then enables the interface as master or slave. Resets the TX and RX DMA channels to -1.

i2s_index_type¶

I2S instance index.

無名列挙型¶

Command codes for hal_i2s_control().

interface_mode_t¶

I2S interface (frame) format.

i2s_frame_size_t¶

Frame (slot) size per channel.

i2s_data_size_t¶

Sample (data) size.

i2s_channel_num_t¶

Number of channels per frame.

i2s_mode_t¶

Clock role.

i2s_device_t¶

I2S configuration and run-time state.

Pass a filled copy to hal_i2s_setConfig() before hal_i2s_init().

マクロ¶

i2s_config.h¶

#include "i2s_config.h"（ソースコード）

Fixed I2S options applied by hal_i2s_init().

マクロ¶