STM32F769NI USB CDC host problem sending simple data to the device - embedded

Question

I am making HID for some data acquisition system. There are a lot of sensors who store test data and when I need I get to them and connect via USB and take it. USB host sent 3 bytes and USB device, if bytes are correct, sends its stored data. Sounds simple.
Previously it was implemented on PC, but now I try to implement it on STM32F769 Discovery and have some serious problems.
I am using ARM Keil 5.27, code generated with STM32CubeMX 5.3.0. I tried just to make a plain simple program, later to integrate with the entire touchscreen interface. I tried to implement this code in main:
if (HAL_GPIO_ReadPin(BUTTON_GPIO_Port, BUTTON_Pin))
while (HAL_GPIO_ReadPin(BUTTON_GPIO_Port, BUTTON_Pin))
{
Transmission_function();
}
And the function itself:
#define DLE 0x10
#define STX 0x2
uint8_t tx_buf[]={DLE, STX, 120}, RX_FLAG;
uint32_t size_tx=sizeof(tx_buf);
void Transmission_function (void)
{
if (Appli_state == APPLICATION_READY)
{
i=0;
USBH_CDC_Transmit(&hUsbHostHS, tx_buf, size_tx);
HAL_Delay(50);
RX_FLAG=0;
}
}
It should send the message after I press the blue button on the Discovery board. All that I get is Hard Fault. While trying to debug, I tried manually to check after which action I get this error and it was functioning in stm32f7xx_ll_usb.c:
HAL_StatusTypeDef USB_WritePacket(USB_OTG_GlobalTypeDef *USBx, uint8_t *src,
uint8_t ch_ep_num, uint16_t len, uint8_t dma)
{
uint32_t USBx_BASE = (uint32_t)USBx;
uint32_t *pSrc = (uint32_t *)src;
uint32_t count32b, i;
if (dma == 0U)
{
count32b = ((uint32_t)len + 3U) / 4U;
for (i = 0U; i < count32b; i++)
{
USBx_DFIFO((uint32_t)ch_ep_num) = *((__packed uint32_t *)pSrc);
pSrc++;
}
}
return HAL_OK;
}
But trying to scroll back in disassembly I notice, that just before Hard Fault program was in this function inside stm32f7xx_hal_hcd.c, in case GRXSTS_PKTSTS_IN:
static void HCD_RXQLVL_IRQHandler(HCD_HandleTypeDef *hhcd)
{
USB_OTG_GlobalTypeDef *USBx = hhcd->Instance;
uint32_t USBx_BASE = (uint32_t)USBx;
uint32_t pktsts;
uint32_t pktcnt;
uint32_t temp;
uint32_t tmpreg;
uint32_t ch_num;
temp = hhcd->Instance->GRXSTSP;
ch_num = temp & USB_OTG_GRXSTSP_EPNUM;
pktsts = (temp & USB_OTG_GRXSTSP_PKTSTS) >> 17;
pktcnt = (temp & USB_OTG_GRXSTSP_BCNT) >> 4;
switch (pktsts)
{
case GRXSTS_PKTSTS_IN:
/* Read the data into the host buffer. */
if ((pktcnt > 0U) && (hhcd->hc[ch_num].xfer_buff != (void *)0))
{
(void)USB_ReadPacket(hhcd->Instance, hhcd->hc[ch_num].xfer_buff, (uint16_t)pktcnt);
/*manage multiple Xfer */
hhcd->hc[ch_num].xfer_buff += pktcnt;
hhcd->hc[ch_num].xfer_count += pktcnt;
if ((USBx_HC(ch_num)->HCTSIZ & USB_OTG_HCTSIZ_PKTCNT) > 0U)
{
/* re-activate the channel when more packets are expected */
tmpreg = USBx_HC(ch_num)->HCCHAR;
tmpreg &= ~USB_OTG_HCCHAR_CHDIS;
tmpreg |= USB_OTG_HCCHAR_CHENA;
USBx_HC(ch_num)->HCCHAR = tmpreg;
hhcd->hc[ch_num].toggle_in ^= 1U;
}
}
break;
case GRXSTS_PKTSTS_DATA_TOGGLE_ERR:
break;
case GRXSTS_PKTSTS_IN_XFER_COMP:
case GRXSTS_PKTSTS_CH_HALTED:
default:
break;
}
}
Last few lines from Dissasembly shows this:
0x080018B4 E8BD81F0 POP {r4-r8,pc}
0x080018B8 0000 DCW 0x0000
0x080018BA 1FF8 DCW 0x1FF8
Why it fails? How could I fix it? I do not have much experience with USB protocol.

Answer 1

I will post my walkaround this, but I am not sure why it worked. Solution was to use EXTI0 interrupt instead of just detection if PA0 is high, as I showed I used here:
if (HAL_GPIO_ReadPin(BUTTON_GPIO_Port, BUTTON_Pin))
while (HAL_GPIO_ReadPin(BUTTON_GPIO_Port, BUTTON_Pin))
Transmission_function();
I changed it to this:
void EXTI0_IRQHandler(void)
{
/* USER CODE BEGIN EXTI0_IRQn 0 */
if(Appli_state == APPLICATION_READY){
USBH_CDC_Transmit(&hUsbHostHS, Buffer, 3);
}
/* USER CODE END EXTI0_IRQn 0 */
HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_0);
/* USER CODE BEGIN EXTI0_IRQn 1 */
/* USER CODE END EXTI0_IRQn 1 */
}