nRF5 audio

Audio devices of the nRF52: the PDM and I2S interfaces. More...

Data Structures
struct	pbl_audio_nrf5_pdm
	PDM interface. More...
struct	pbl_audio_nrf5_i2s
	I2S interface. More...

Macros
#define	PBL_AUDIO_NRF5_PDM_DEFINE(sym, _name, _clk, _din, _default_gain_mdb)
	Define the PDM interface, a capture device.
#define	PBL_AUDIO_NRF5_I2S_BOUNCE_FRAMES   512U
	Stereo frames of an I2S bounce buffer.
#define	PBL_AUDIO_NRF5_I2S_DEFINE(sym, _name, _link, ...)
	Define the I2S interface, a playback device.

Functions
void	pbl_audio_nrf5_pdm_irq_handler (const struct pbl_audio_nrf5_pdm *pdm)
	PDM interrupt handler, to connect with PBL_IRQ_CONNECT().
void	pbl_audio_nrf5_i2s_irq_handler (const struct pbl_audio_nrf5_i2s *i2s)
	I2S interrupt handler, to connect with PBL_IRQ_CONNECT().

Detailed Description

Audio devices of the nRF52: the PDM and I2S interfaces.

The PDM interface records one or two digital microphones at 16 kHz from a 1.28 MHz clock; its gain runs from -20 to +20 dB. The I2S interface plays mono at 16 kHz, sent as stereo with both channels equal, and runs as a slave when the link has PBL_AUDIO_FMT_CODEC_MASTER, still providing a 4 MHz master clock. Both keep the high-frequency crystal on while streaming.

PBL_IRQ_CONNECT(PDM, 7, pbl_audio_nrf5_pdm_irq_handler, &s_mic, 0);
PBL_IRQ_CONNECT(I2S, 5, pbl_audio_nrf5_i2s_irq_handler, &s_speaker, 0);

---

Data Structure Documentation

pbl_audio_nrf5_pdm

struct pbl_audio_nrf5_pdm

PDM interface.

Data Fields
struct pbl_audio	audio	Audio device.
struct pbl_gpio	clk	Clock pin.
int32_t	default_gain_mdb	Gain after initialization, in mdB.
struct pbl_gpio	din	Data pin.
struct pbl_audio_nrf5_pdm_state *	state	Driver runtime state.

pbl_audio_nrf5_i2s

struct pbl_audio_nrf5_i2s

I2S interface.

Data Fields
struct pbl_audio	audio	Audio device.
struct pbl_gpio	lrck	Frame clock pin.
struct pbl_gpio	mck	Master clock pin.
struct pbl_gpio	sck	Bit clock pin.
struct pbl_gpio	sdout	Data out pin.
struct pbl_audio_nrf5_i2s_state *	state	Driver runtime state.

Macro Definition Documentation

PBL_AUDIO_NRF5_I2S_BOUNCE_FRAMES

#define PBL_AUDIO_NRF5_I2S_BOUNCE_FRAMES   512U

Stereo frames of an I2S bounce buffer.

PBL_AUDIO_NRF5_I2S_DEFINE

#define PBL_AUDIO_NRF5_I2S_DEFINE	(		sym,
			_name,
			_link,
			...
	)

Value:

  PBL_AUDIO_STATE_DEFINE(sym);                                                                   \
  static struct pbl_audio_nrf5_i2s_state sym##_i2s_state;                                        \
  static const struct pbl_audio_nrf5_i2s sym = {                                                 \
    .audio =                                                                                     \
        PBL_AUDIO_INIT(sym, _name, PBL_AUDIO_PLAYBACK, &pbl_audio_nrf5_i2s_ops, _link, nullptr), \
    .state = &sym##_i2s_state,                                                                   \
    __VA_ARGS__                                                                                  \
  };                                                                                             \
  PBL_DEVICE_REGISTER(sym, &sym.audio.dev)

Define the I2S interface, a playback device.

Periods are copied into stereo bounce buffers, so a period must fit one.

Parameters

sym	Symbol of the device.
_name	Device name.
_link	What the interface is wired to.
...	Pins: sck, lrck, mck and sdout, from PBL_GPIO().

PBL_AUDIO_NRF5_PDM_DEFINE

#define PBL_AUDIO_NRF5_PDM_DEFINE	(		sym,
			_name,
			_clk,
			_din,
			_default_gain_mdb
	)

Value:

  PBL_AUDIO_STATE_DEFINE(sym);                                                                    \
  static struct pbl_audio_nrf5_pdm_state sym##_pdm_state;                                         \
  static const struct pbl_audio_nrf5_pdm sym = {                                                  \
    .audio =                                                                                      \
        PBL_AUDIO_INIT(sym, _name, PBL_AUDIO_CAPTURE, &pbl_audio_nrf5_pdm_ops, nullptr, nullptr), \
    .clk = _clk,                                                                                  \
    .din = _din,                                                                                  \
    .default_gain_mdb = (_default_gain_mdb),                                                      \
    .state = &sym##_pdm_state,                                                                    \
  };                                                                                              \
  PBL_DEVICE_REGISTER(sym, &sym.audio.dev)

Define the PDM interface, a capture device.

Parameters

sym	Symbol of the device.
_name	Device name.
_clk	Clock pin, from PBL_GPIO().
_din	Data pin, from PBL_GPIO().
_default_gain_mdb	Gain after initialization, in mdB.

Function Documentation

pbl_audio_nrf5_i2s_irq_handler()

void pbl_audio_nrf5_i2s_irq_handler

(

const struct pbl_audio_nrf5_i2s *

i2s

)

I2S interrupt handler, to connect with PBL_IRQ_CONNECT().

Parameters

i2s	I2S interface.

pbl_audio_nrf5_pdm_irq_handler()

void pbl_audio_nrf5_pdm_irq_handler

(

const struct pbl_audio_nrf5_pdm *

pdm

)

PDM interrupt handler, to connect with PBL_IRQ_CONNECT().

Parameters

pdm	PDM interface.