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Add method to obtain precise audio sample rate
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Actual LRClk I2S sample rate is not precisely
equal to the "ideal" sample rate due to
peripheral clock division requirements.

This adds a method to return a float
representing the "actual" hardware
audio sample rate for more precise DSP
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@ndonald2
ndonald2 committed May 16, 2024
1 parent f7727ed commit 11b5b84
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Showing 4 changed files with 84 additions and 42 deletions.
13 changes: 12 additions & 1 deletion src/hid/audio.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@ class AudioHandle::Impl
// Interface
AudioHandle::Result Init(const AudioHandle::Config config, SaiHandle sai);
AudioHandle::Result
Init(const AudioHandle::Config config, SaiHandle sai1, SaiHandle sai2);
Init(const AudioHandle::Config config, SaiHandle sai1, SaiHandle sai2);
AudioHandle::Result DeInit();
AudioHandle::Result Start(AudioHandle::AudioCallback callback);
AudioHandle::Result Start(AudioHandle::InterleavingAudioCallback callback);
Expand Down Expand Up @@ -60,6 +60,12 @@ class AudioHandle::Impl

float GetSampleRate() { return sai1_.GetSampleRate(); }

float GetPreciseSampleRate(uint32_t sai_idx)
{
return sai_idx == 0 ? sai1_.GetPreciseSampleRate()
: sai2_.GetPreciseSampleRate();
}

AudioHandle::Result SetPostGain(float val)
{
if(val <= 0.f)
Expand Down Expand Up @@ -525,6 +531,11 @@ float AudioHandle::GetSampleRate()
return pimpl_->GetSampleRate();
}

float AudioHandle::GetPreciseSampleRate(uint32_t sai_idx)
{
return pimpl_->GetPreciseSampleRate(sai_idx);
}

AudioHandle::Result
AudioHandle::SetSampleRate(SaiHandle::Config::SampleRate samplerate)
{
Expand Down
33 changes: 19 additions & 14 deletions src/hid/audio.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,9 @@
namespace daisy
{
/** @brief Audio Engine Handle
* @ingroup audio
* @ingroup audio
* @details This class allows for higher level access to an audio engine.
* If you're using a SOM like the DaisySeed or DaisyPatchSM (or any
* If you're using a SOM like the DaisySeed or DaisyPatchSM (or any
* board that includes one of those objects) then the intialization
* is already taken care of.
* If you're setting up your own custom hardware, or need to make changes
Expand Down Expand Up @@ -49,17 +49,17 @@ class AudioHandle
};

/** Non-Interleaving input buffer
* Buffer arranged by float[chn][sample]
* Buffer arranged by float[chn][sample]
* const so that the user can't modify the input
*/
typedef const float* const* InputBuffer;

/** Non-Interleaving output buffer
* Arranged by float[chn][sample]
* Arranged by float[chn][sample]
*/
typedef float** OutputBuffer;

/** Type for a Non-Interleaving audio callback
/** Type for a Non-Interleaving audio callback
* Non-Interleaving audio callbacks in daisy will be of this type
*/
typedef void (*AudioCallback)(InputBuffer in,
Expand All @@ -72,12 +72,12 @@ class AudioHandle
*/
typedef const float* InterleavingInputBuffer;

/** Interleaving Output buffer
/** Interleaving Output buffer
** audio is prepared as { L0, R0, L1, R1, . . . LN, RN }
*/
typedef float* InterleavingOutputBuffer;

/** Interleaving Audio Callback
/** Interleaving Audio Callback
* Interleaving audio callbacks in daisy must be of this type
*/
typedef void (*InterleavingAudioCallback)(InterleavingInputBuffer in,
Expand All @@ -102,7 +102,7 @@ class AudioHandle
/** Returns the Global Configuration struct for the Audio */
const Config& GetConfig() const;

/** Returns the number of channels of audio.
/** Returns the number of channels of audio.
**
** When using a single SAI this returns 2, when using two SAI it returns 4
** If no SAI is initialized this returns 0
Expand All @@ -111,20 +111,25 @@ class AudioHandle
*/
size_t GetChannels() const;

/** Returns the Samplerate as a float */
/** Returns the (idealized) Samplerate as a float */
float GetSampleRate();

/** Returns the actual, hardware-precise Samplerate as a float
* @param sai_idx The index (0 or 1) of the SAI to use as the source of the sample rate.
*/
float GetPreciseSampleRate(uint32_t sai_idx = 0);

/** Sets the samplerate, and reinitializes the sai as needed. */
Result SetSampleRate(SaiHandle::Config::SampleRate samplerate);

/** Sets the block size after initialization, and updates the internal configuration struct.
** Get BlockSize and other details via the GetConfig
** Get BlockSize and other details via the GetConfig
*/
Result SetBlockSize(size_t size);

/** Sets the amount of gain adjustment to perform before and after callback.
** useful if the hardware has additional headroom, and the nominal value shouldn't be 1.0
**
** useful if the hardware has additional headroom, and the nominal value shouldn't be 1.0
**
** \param val Gain adjustment amount. The hardware will clip at the reciprical of this value. */
Result SetPostGain(float val);

Expand All @@ -139,8 +144,8 @@ class AudioHandle
/** Starts the Audio using the non-interleaving callback. */
Result Start(AudioCallback callback);

/** Starts the Audio using the interleaving callback.
** For now only two channels are supported via this method.
/** Starts the Audio using the interleaving callback.
** For now only two channels are supported via this method.
*/
Result Start(InterleavingAudioCallback callback);

Expand Down
45 changes: 33 additions & 12 deletions src/per/sai.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@ class SaiHandle::Impl

// Utility functions
float GetSampleRate();
float GetPreciseSampleRate() const;
size_t GetBlockSize();
float GetBlockRate();

Expand All @@ -43,6 +44,9 @@ class SaiHandle::Impl
/** Offset stored for weird inter-SAI stuff.*/
size_t dma_offset;

/** Precise sample rate based on peripheral clock division */
float sr_precise;

/** Callback that dispatches user callback from Cplt and HalfCplt DMA Callbacks */
void InternalCallback(size_t offset);

Expand Down Expand Up @@ -201,6 +205,14 @@ SaiHandle::Result SaiHandle::Impl::Init(const SaiHandle::Config& config)
return Result::ERR;
}

uint32_t per_freq = (sai_idx == 0)
? HAL_RCCEx_GetPeriphCLKFreq(RCC_PERIPHCLK_SAI1)
: HAL_RCCEx_GetPeriphCLKFreq(RCC_PERIPHCLK_SAI2);
uint32_t mck_div = sai_a_handle_.Init.Mckdiv;

// Actual LRClk sample rate is subject to integer peripheral clock division
sr_precise = static_cast<float>(per_freq) / (mck_div * 256.0f);

return Result::OK;
}

Expand Down Expand Up @@ -230,10 +242,10 @@ void SaiHandle::Impl::InitDma(PeripheralBlock block)
hsai = &sai_a_handle_;
hdma = &sai_a_dma_handle_;
dir = config_.a_dir == Config::Direction::RECEIVE
? DMA_PERIPH_TO_MEMORY
: DMA_MEMORY_TO_PERIPH;
req = sai_idx == int(Config::Peripheral::SAI_1) ? DMA_REQUEST_SAI1_A
: DMA_REQUEST_SAI2_A;
? DMA_PERIPH_TO_MEMORY
: DMA_MEMORY_TO_PERIPH;
req = sai_idx == int(Config::Peripheral::SAI_1) ? DMA_REQUEST_SAI1_A
: DMA_REQUEST_SAI2_A;

if(sai_idx == int(Config::Peripheral::SAI_1))
hdma->Instance = DMA1_Stream0;
Expand All @@ -245,10 +257,10 @@ void SaiHandle::Impl::InitDma(PeripheralBlock block)
hsai = &sai_b_handle_;
hdma = &sai_b_dma_handle_;
dir = config_.b_dir == Config::Direction::RECEIVE
? DMA_PERIPH_TO_MEMORY
: DMA_MEMORY_TO_PERIPH;
req = sai_idx == int(Config::Peripheral::SAI_1) ? DMA_REQUEST_SAI1_B
: DMA_REQUEST_SAI2_B;
? DMA_PERIPH_TO_MEMORY
: DMA_MEMORY_TO_PERIPH;
req = sai_idx == int(Config::Peripheral::SAI_1) ? DMA_REQUEST_SAI1_B
: DMA_REQUEST_SAI2_B;

if(sai_idx == int(Config::Peripheral::SAI_1))
hdma->Instance = DMA1_Stream1;
Expand Down Expand Up @@ -349,6 +361,10 @@ float SaiHandle::Impl::GetSampleRate()
default: return 48000.f;
}
}
float SaiHandle::Impl::GetPreciseSampleRate() const
{
return sr_precise;
}
size_t SaiHandle::Impl::GetBlockSize()
{
// Buffer handled in halves, 2 samples per frame (1 per channel)
Expand All @@ -365,10 +381,10 @@ void SaiHandle::Impl::InitPins()
GPIO_InitTypeDef GPIO_InitStruct;
GPIO_TypeDef* port;
dsy_gpio_pin* cfg[] = {&config_.pin_config.fs,
&config_.pin_config.mclk,
&config_.pin_config.sck,
&config_.pin_config.sa,
&config_.pin_config.sb};
&config_.pin_config.mclk,
&config_.pin_config.sck,
&config_.pin_config.sa,
&config_.pin_config.sb};
// Special Case checks
dsy_gpio_pin sck_af_pin = {DSY_GPIOA, 2};
is_master = (config_.a_sync == Config::Sync::MASTER
Expand Down Expand Up @@ -570,6 +586,11 @@ float SaiHandle::GetSampleRate()
return pimpl_->GetSampleRate();
}

float SaiHandle::GetPreciseSampleRate()
{
return pimpl_->GetPreciseSampleRate();
}

size_t SaiHandle::GetBlockSize()
{
return pimpl_->GetBlockSize();
Expand Down
35 changes: 20 additions & 15 deletions src/per/sai.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,20 +6,20 @@

namespace daisy
{
/**
/**
* Support for I2S Audio Protocol with different bit-depth, samplerate options
* Allows for master or slave, as well as freedom of selecting direction,
* Allows for master or slave, as well as freedom of selecting direction,
* and other behavior for each peripheral, and block.
*
*
* DMA Transfer commands must use buffers located within non-cached memory or use cache maintenance
* To declare an unitialized global element in the DMA memory section:
* int32_t DSY_DMA_BUFFER_SECTOR my_buffer[96];
*
* Callback functions will be called once per half of the buffer. In the above example,
* Callback functions will be called once per half of the buffer. In the above example,
* the callback function would be called once for every 48 samples.
*
*
* Use SAI Handle like this:
*
*
* SaiHandle::Config sai_config;
* sai_config.periph = SaiHandle::Config::Peripheral::SAI_1;
* sai_config.sr = SaiHandle::Config::SampleRate::SAI_48KHZ;
Expand Down Expand Up @@ -70,7 +70,7 @@ class SaiHandle
SAI_32BIT,
};

/** Specifies whether a particular block is the master or the slave
/** Specifies whether a particular block is the master or the slave
** If both are set to slave, no MCLK signal will be used, and it is
** expected that the codec will have its own xtal.
*/
Expand Down Expand Up @@ -118,16 +118,16 @@ class SaiHandle
/** Returns the current configuration */
const Config& GetConfig() const;

/** Callback Function to be called when DMA transfer is complete and half complete.
/** Callback Function to be called when DMA transfer is complete and half complete.
** This callback is prepared however the data is transmitted/received from the device.
** For example, using an AK4556 the data will be interleaved 24bit MSB Justified
**
**
** The hid/audio class will be allow for type conversions, de-interleaving, etc.
*/
typedef void (*CallbackFunctionPtr)(int32_t* in, int32_t* out, size_t size);

/** Starts Rx and Tx in Circular Buffer Mode
** The callback will be called when half of the buffer is ready,
/** Starts Rx and Tx in Circular Buffer Mode
** The callback will be called when half of the buffer is ready,
** and will handle size/2 samples per callback.
*/
Result StartDma(int32_t* buffer_rx,
Expand All @@ -138,15 +138,20 @@ class SaiHandle
/** Stops the DMA stream for the SAI blocks in use. */
Result StopDma();

/** Returns the samplerate based on the current configuration */
/** Returns the (idealized) samplerate based on the current configuration */
float GetSampleRate();

/** Returns the number of samples per audio block
/** Returns the exact samplerate based on the current configuration.
* This is only valid after successful initialization.
*/
float GetPreciseSampleRate();

/** Returns the number of samples per audio block
** Calculated as Buffer Size / 2 / number of channels */
size_t GetBlockSize();

/** Returns the Block Rate of the current stream based on the size
** of the buffer passed in, and the current samplerate.
/** Returns the Block Rate of the current stream based on the size
** of the buffer passed in, and the current samplerate.
*/
float GetBlockRate();

Expand Down

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