STM32H747I-DISCO: SAI DMA Returns Transfer Error

[miloa]

Hello,

I am trying to fill a buffer from the on-board MEMS microphone using the BSP_AUDIO_IN_RecordPDM() function. However, execution pauses around HAL_SAI_Receive_DMA() and the BSP_AUDIO_IN_IRQHandler() is called. The stack trace is as follows:

Checking the hdma variable on the debugger, I can see the error code is 1, corresponding (I believe) to a transfer error. I tried looking at the relevant registers with breakpoints, but they were at 0x0 at every point:

I've tried almost everything under the sun. I disabled the D-Cache and allocated all the memory to RAM_D1, I tried allocating my buffer (copied below) to each of RAM_D1, D2, and D3

ALIGN_32BYTES (uint16_t recordPDMBuf[AUDIO_IN_PDM_BUFFER_SIZE]) __attribute__((section(".RAM_D1")));

My linker script looks like this:

/* Highest address of the user mode stack */
_estack = ORIGIN(RAM_D1) + LENGTH(RAM_D1); /* end of "RAM_D1" Ram type memory */

_Min_Heap_Size = 0x800 ; /* required amount of heap */
_Min_Stack_Size = 0x800 ; /* required amount of stack */

/* Memories definition */
MEMORY
{
 RAM_D1 (xrw) : ORIGIN = 0x24000000, LENGTH = 512K
 FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 1024K /* Memory is divided. Actual start is 0x08000000 and actual length is 2048K */
 DTCMRAM (xrw) : ORIGIN = 0x20000000, LENGTH = 128K
 RAM_D2 (xrw) : ORIGIN = 0x30000000, LENGTH = 288K
 RAM_D3 (xrw) : ORIGIN = 0x38000000, LENGTH = 64K
 ITCMRAM (xrw) : ORIGIN = 0x00000000, LENGTH = 64K
}

/* ... */ 

/* Initialized data sections into "RAM" Ram type memory */
 .data :
 {
 . = ALIGN(4);
 _sdata = .; /* create a global symbol at data start */
 *(.data) /* .data sections */
 *(.data*) /* .data* sections */
 *(.RamFunc) /* .RamFunc sections */
 *(.RamFunc*) /* .RamFunc* sections */

 . = ALIGN(4);
 _edata = .; /* define a global symbol at data end */
 } >RAM_D1 AT> FLASH

 /* Uninitialized data section into "RAM" Ram type memory */
 . = ALIGN(4);
 .bss :
 {
 /* This is used by the startup in order to initialize the .bss section */
 _sbss = .; /* define a global symbol at bss start */
 __bss_start__ = _sbss;
 *(.bss)
 *(.bss*)
 *(COMMON)

 . = ALIGN(4);
 _ebss = .; /* define a global symbol at bss end */
 __bss_end__ = _ebss;
 } >RAM_D1

 /* User_heap_stack section, used to check that there is enough "RAM" Ram type memory left */
 ._user_heap_stack :
 {
 . = ALIGN(8);
 PROVIDE ( end = . );
 PROVIDE ( _end = . );
 . = . + _Min_Heap_Size;
 . = . + _Min_Stack_Size;
 . = ALIGN(8);
 } >RAM_D1

 

 At this point, I'm not entirely sure what to do. Any help is greatly appreciated. Lastly, in case it is useful, here are all the configured peripherals in main.c:

MX_GPIO_Init();
MX_SAI1_Init();
MX_DMA2D_Init();
MX_DSIHOST_DSI_Init();
MX_LTDC_Init();
MX_FMC_Init();
MX_USART1_UART_Init();
MX_SPI2_Init();
MX_X_CUBE_AI_Init();

[miloa]

Update: also configured the DMA module in CubeMX so that is included in the initialization as well. Did not really fix anything.

[TDK]

Where exactly is Error_Handler being called and why? Stack trace is there, should be easy to find out.

 

[miloa]

Sorry, I'm not entirely sure I understand. I've only been using the IDE for a few weeks so I may be missing something. Is there something I can print out from inside the Error_Handler to help me debug? The function itself takes in no arguments.

Unless you mean following the stack trace, in which case it looks like the HAL_SAI_Receive_DMA() function is erroring in line 9 in the code below (although it sometimes errors in line 16). After that the stack trace has a "signal handler" at 0xffffffe9 which the IDE is unable to show me, and after that it enters the cascade of interrupt handlers.

...
 /* Enable the interrupts for error handling */
 __HAL_SAI_ENABLE_IT(hsai, SAI_InterruptFlag(hsai, SAI_MODE_DMA));

 /* Enable SAI Rx DMA Request */
 hsai->Instance->CR1 |= SAI_xCR1_DMAEN;

 /* Check if the SAI is already enabled */
 if ((hsai->Instance->CR1 & SAI_xCR1_SAIEN) == 0U)
 {
 /* Enable SAI peripheral */
 __HAL_SAI_ENABLE(hsai);
 }

 /* Process Unlocked */
 __HAL_UNLOCK(hsai);

 return HAL_OK;
...

 

[TDK]

So keep going down the chain until you see why it was called.

HAL_SAI_Receive_DMA is in the main thread, before the interrupt happened. Error handler was called within the interrupt.

[TDK]

It could be that your buffer is located in a place that DMA cannot access.

[miloa]

That's what I've been thinking, but I don't know what I might be doing wrong in that regard. That's why I posted my linker script and buffer location.

[miloa]

Okay! So the issue in this case was that DMA uses SAI4 and not SAI1. After fixing the issue with CubeMX I'm still reaching the error handler but at least it's a different error now: an SAI ErrorCode 2 (underrun)

[miloa]

I've been running in circles for a few days now... I tried loading in the BSP SAI audio playback example and the buffer was still just getting filled with zeroes. I'm convinced my microphones are somehow broken.