Audio Transfer Callbacks not executing with STM32F469I-Discovery - c

Question

I'm new to embedded programming and I'm currently working on a project with an STM32F469I-discovery board. I'm using eclipse with the ARM tool chain and the supplied drivers. I'm getting stuck on playing a binary audio file flashed into the chip at a specific address. I've very simply based my code on some of the example files, although very much cut down as I'm just trying to get it to work.
At the moment, the code works up to the point where it plays the buffer, but then it appears to get stuck. The buffer is playing in a loop (I've changed the size of the buffer to confirm this) and you can hear it, but that's all that happens. The transfer interrupt callbacks never execute, and hence the buffer does not refil and the full sample is never played.
I've tried using an external interupt to refil the buffer, but when I try this, it gets stuck. I've also tried to debug it by turning on LEDs, but this has confirmed that effectively it gets stuck shortly after playing the sample. The infinite while loop never executes, and the transfer interrupts never execute.
My question is - why is it getting stuck and why are the interrupts not being triggered?
Any help would be greatly appreciated!
#include "main.h"
static void SystemClock_Config(void);
#define AUDIO_FILE_ADDRESS 0x08010000
#define AUDIO_FILE_SIZE (180*1024)
#define PLAY_HEADER 0x2C
#define PBSIZE 4096
uint16_t PlayBuff[PBSIZE];
int OFFSET = 0;
int TransferState = 0;
int CycleCount1 = 1;
int CycleCount2 = 1;
int main(void)
{
uint32_t PlaybackPosition = PBSIZE + PLAY_HEADER;
HAL_Init();
/* Configure the system clock to 180 MHz */
SystemClock_Config();
// Fill the buffer first time round
for(int i=0; i <= PBSIZE; i++)
{
PlayBuff[i]=*((__IO uint16_t *)(AUDIO_FILE_ADDRESS + PLAY_HEADER + i));
}
BSP_AUDIO_OUT_Init(2,50,AUDIO_FREQUENCY_16K );
BSP_AUDIO_OUT_Play(PlayBuff,PBSIZE);
while(1){
if(TransferState==1){
// refill the first part of the buffer
TransferState=0;
OFFSET = CycleCount1*PBSIZE;
for(int i=0; i <= PBSIZE/2; i++){
PlayBuff[i]=*((__IO uint16_t *)(AUDIO_FILE_ADDRESS + PLAY_HEADER + OFFSET));
}
CycleCount1++;
}
if(TransferState==2){
// refill the second part of the buffer
OFFSET = CycleCount2*PBSIZE+PBSIZE;
TransferState=0;
for(int i=PBSIZE/2; i <= PBSIZE; i++){
PlayBuff[i]=*((__IO uint16_t *)(AUDIO_FILE_ADDRESS + PLAY_HEADER + OFFSET));
}
CycleCount2++;
}
}
}
void BSP_AUDIO_OUT_TransferComplete_CallBack(void)
{
TransferState=2;
}
void BSP_AUDIO_OUT_HalfTransfer_CallBack(void){
TransferState=1;
}
In the interests of identifying the cause of the problem, I've further trimmed down the code so that all it does is play the buffer. I've removed the interrupt calls to try and identify what's causing the issue.
What it should do is configure the system clock, fill the buffer, initialise the audio, then turn on the LED. It should then play the audio buffer, wait 1s, then turn off the LED. It plays the buffer in a loop (as it should as it's in circular mode) but then gets stuck and never turns off the LED. I've tried running it in normal mode but it simply plays the buffer once, and then gets stuck.
This leads me to think I've configured/filled the buffer incorrectly.
#include "main.h"
static void SystemClock_Config(void);
#define AUDIO_FILE_ADDRESS 0x08010000
#define PLAY_HEADER 0x17569
#define PBSIZE 4096
uint16_t PlayBuff[PBSIZE];
int main(void)
{
BSP_LED_Init(LED1);
HAL_Init();
/* Configure the system clock to 180 MHz */
SystemClock_Config();
// Fill the buffer first time round
for(int i=0; i <= PBSIZE; i++)
{
PlayBuff[i]=*((__IO uint16_t *)(AUDIO_FILE_ADDRESS + PLAY_HEADER + i));
}
BSP_AUDIO_OUT_Init(OUTPUT_DEVICE_HEADPHONE ,50,AUDIO_FREQUENCY_44K );
BSP_LED_On(LED1);
BSP_AUDIO_OUT_Play(PlayBuff,PBSIZE);
HAL_Delay(1000);
BSP_LED_Off(LED1);
}
Furthermore, I've also found instances of other people online having similar issues although with no solution so far. Any help would be greatly appreciated.

Answer 1

I've found the problem. I hadn't set the DMA interupt in the stm32f4xx_it.c.
void DMA2_Stream3_IRQHandler(void)
{
HAL_DMA_IRQHandler(haudio_out_sai.hdmatx);
}
I've also found that when using BSP_AUDIO_OUT_Play() the sound is wrong with something bassy fluctating underneath it.
Using the following worked correctly.
/* Start the playback */
if(0 != audio_drv->Play(AUDIO_I2C_ADDRESS, NULL, 0))
{
Error_Handler();
}
if(HAL_OK != HAL_SAI_Transmit_DMA(&haudio_out_sai, (uint8_t *) PlayBuff, PLAY_BUFF_SIZE))
{
Error_Handler();
}

Answer 2

I am not familiar with the specific board, from what i see possibly you need to define TransferState as volatile.
volatile int TransferState = 0;
It is quite common issue in embedded and multi-threaded development. The compiler can optimize the variable TransferState in a register so it never actually sees the update from a different context(the callback). Volatile prevents it from doing so