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extmod/machine_i2s: Factor comments, some enums and macros.

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Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George
2023-10-10 16:44:02 +11:00
parent 46ae3b5a34
commit 91a3f18391
5 changed files with 52 additions and 188 deletions
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49
ports/stm32/machine_i2s.c
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@@ -33,39 +33,8 @@
#include "pin.h"
#include "dma.h"
#if MICROPY_PY_MACHINE_I2S
// The I2S module has 3 modes of operation:
//
// Mode1: Blocking
// - readinto() and write() methods block until the supplied buffer is filled (read) or emptied (write)
// - this is the default mode of operation
//
// Mode2: Non-Blocking
// - readinto() and write() methods return immediately
// - buffer filling and emptying happens asynchronously to the main MicroPython task
// - a callback function is called when the supplied buffer has been filled (read) or emptied (write)
// - non-blocking mode is enabled when a callback is set with the irq() method
// Notes on this port's specific implementation of I2S:
// - the DMA callbacks (1/2 complete and complete) are used to implement the asynchronous background operations
//
// Mode3: Asyncio
// - implements the stream protocol
// - asyncio mode is enabled when the ioctl() function is called
// - the state of the internal ring buffer is used to detect that I2S samples can be read or written
//
// The samples contained in the app buffer supplied for the readinto() and write() methods have the following convention:
// Mono: little endian format
// Stereo: little endian format, left channel first
//
// I2S terms:
// "frame": consists of two audio samples (Left audio sample + Right audio sample)
//
// Misc:
// - for Mono configuration:
// - readinto method: samples are gathered from the L channel only
// - write method: every sample is output to both the L and R channels
// - for readinto method the I2S hardware is read using 8-byte frames
// (this is standard for almost all I2S hardware, such as MEMS microphones)
// - all 3 Modes of operation are implemented using the HAL I2S Generic Driver
// - all sample data transfers use DMA
// - the DMA controller is configured in Circular mode to fulfil continuous and gapless sample flows
@@ -86,20 +55,6 @@
#define NON_BLOCKING_RATE_MULTIPLIER (4)
#define SIZEOF_NON_BLOCKING_COPY_IN_BYTES (SIZEOF_HALF_DMA_BUFFER_IN_BYTES * NON_BLOCKING_RATE_MULTIPLIER)
#define NUM_I2S_USER_FORMATS (4)
#define I2S_RX_FRAME_SIZE_IN_BYTES (8)
typedef enum {
MONO,
STEREO
} format_t;
typedef enum {
BLOCKING,
NON_BLOCKING,
ASYNCIO
} io_mode_t;
typedef enum {
TOP_HALF,
BOTTOM_HALF
@@ -618,5 +573,3 @@ STATIC void mp_machine_i2s_irq_update(machine_i2s_obj_t *self) {
}
MP_REGISTER_ROOT_POINTER(struct _machine_i2s_obj_t *machine_i2s_obj[MICROPY_HW_MAX_I2S]);
#endif // MICROPY_PY_MACHINE_I2S