Why does USB OTG cause X-CUBE AI (5.2.0) to hard fault on inference?
I'm trying to deploy an object detection system on the STM32H743ZI2 board using CubeIDE and X-CUBE AI. For my evaluation process, I want to load images (stored as flattened text file arrays) from a USB flash drive.
To be clear, the USB appears to be set up properly as I can read/write and mount/unmount the USB flash drive without any issues. However, if I mount the USB, it causes the following line of code to hard fault:
nbatch = ai_sine_model_run(sine_model, &ai_input[0], &ai_output[0]);
I've reproduced the rest of the main() code below:
int main(void)
{
/* USER CODE BEGIN 1 */
char buf[50];
int buf_len = 0;
ai_error ai_err;
ai_i32 nbatch;
uint32_t timestamp;
float y_val;
// Chunk of memory used to hold intermediate values for neural network
AI_ALIGNED(4) ai_u8 activations[AI_SINE_MODEL_DATA_ACTIVATIONS_SIZE];
// Buffers used to store input and output tensors
AI_ALIGNED(4) ai_i8 in_data[AI_SINE_MODEL_IN_1_SIZE_BYTES];
AI_ALIGNED(4) ai_i8 out_data[AI_SINE_MODEL_OUT_1_SIZE_BYTES];
// Pointer to our model
ai_handle sine_model = AI_HANDLE_NULL;
// Initialize wrapper structs that hold pointers to data and info about the
// data (tensor height, width, channels)
ai_buffer ai_input[AI_SINE_MODEL_IN_NUM] = AI_SINE_MODEL_IN;
ai_buffer ai_output[AI_SINE_MODEL_OUT_NUM] = AI_SINE_MODEL_OUT;
// Set working memory and get weights/biases from model
ai_network_params ai_params = {
AI_SINE_MODEL_DATA_WEIGHTS(ai_sine_model_data_weights_get()),
AI_SINE_MODEL_DATA_ACTIVATIONS(activations)
};
// Set pointers wrapper structs to our data buffers
ai_input[0].n_batches = 1;
ai_input[0].data = AI_HANDLE_PTR(in_data);
ai_output[0].n_batches = 1;
ai_output[0].data = AI_HANDLE_PTR(out_data);
/* USER CODE END 1 */
/* Enable I-Cache---------------------------------------------------------*/
SCB_EnableICache();
/* Enable D-Cache---------------------------------------------------------*/
SCB_EnableDCache();
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_ETH_Init();
MX_USART3_UART_Init();
MX_FATFS_Init();
MX_USB_HOST_Init();
MX_CRC_Init();
MX_TIM16_Init();
/* USER CODE BEGIN 2 */
// Start timer/counter
HAL_TIM_Base_Start(&htim16);
// Greetings!
buf_len = sprintf(buf, "\r\n\r\nSTM32 X-Cube-AI test\r\n");
printf(buf);
// Create instance of neural network
ai_err = ai_sine_model_create(&sine_model, AI_SINE_MODEL_DATA_CONFIG);
if (ai_err.type != AI_ERROR_NONE)
{
buf_len = sprintf(buf, "Error: could not create NN instance\r\n");
printf(buf);
while(1);
}
// Initialize neural network
if (!ai_sine_model_init(sine_model, &ai_params))
{
buf_len = sprintf(buf, "Error: could not initialize NN\r\n");
printf(buf);
while(1);
}
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
int first_while_iter = 1;
while (1)
{
if (first_while_iter)
{
sprintf(buf, "Mounting USB...\r\n");
printf(buf);
while(1)
{
MX_USB_HOST_Process();
sprintf(name,"num5.bmp");
file_ready = 0;
read_bmp(name);
if(file_ready == 1){
// out_img = ProcessBmp(rtext);
break;
}
}
sprintf(buf, "USB Mounted Successfully\r\n");
printf(buf);
first_while_iter = 0;
}
sprintf(name,"b1.txt");
float * b1 = read_txt(name, 2);
printf("%.2f ", b1[0]);
printf("%.2f\n", b1[1]);
free(b1);
if (f_mount(NULL,USBHPath,0) != FR_OK)
{
Error_Handler();
}
// Fill input buffer (use test value)
for (uint32_t i = 0; i < AI_SINE_MODEL_IN_1_SIZE; i++)
{
((ai_float *)in_data)[i] = (ai_float)2.0f;
}
// Get current timestamp
timestamp = htim16.Instance->CNT;
// Perform inference
nbatch = ai_sine_model_run(sine_model, &ai_input[0], &ai_output[0]);
if (nbatch != 1) {
buf_len = sprintf(buf, "Error: could not run inference\r\n");
printf(buf);
}
// Read output (predicted y) of neural network
y_val = ((float *)out_data)[0];
// Print output of neural network along with inference time (microseconds)
buf_len = sprintf(buf,
"Output: %f | Duration: %lu\r\n",
y_val,
htim16.Instance->CNT - timestamp);
printf(buf);
// Wait before doing it again
HAL_Delay(1000);
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}Because I'm new to X-Cube AI, I consulted this tutorial in addition to consulting the documentation.
The above script is just mounting the USB and loading a dummy text file before performing inference with a very basic model. The model is supposed to approximate sin(x), and the input is hard-coded to 2.0. (The data loaded from the USB is just for testing purposes, it is not used during inference).
The purpose of the test is to make sure that I didn't mess up the hardware configuration ('.ioc') file, and to spot problematic interactions like this.
The USB code works perfectly with and without the X-CUBE AI inference code.
If I comment out the USB code, X-Cube AI works perfectly. However this is not a solution as I need a way to load images onto the board.
Any help/experience with USB OTG and X-Cube AI conflicts would be greatly appreciated.