HAL_PCDEx_SetRxFiFo 和 HAL_PCDEx_SetTxFiFo
這兩個函數的作用是：該EndPoint數據傳輸最大數量的限定
除前面貼子裏廛的影響數據傳輸量的函數外，這兩個HAL_PCDEx_SetRxFiFo / HAL_PCDEx_SetTxFiFo函數也值得注意。
其一，這兩個函數是有使用順序的（參考USBD_LL_Init函數）：HAL_PCDEx_SetRxFiFo先設置GRXFSIZ，然後HAL_PCDEx_SetTxFiFo中會用到這個GRXFSIZ。
另外，所有EP共享的Rx FIFO + 所有的Tx FIFO，最大允許在RAM中開闢的空間爲1.25kB（i.e. max. 0x140 words）
下面的代碼中，Tx_Offset是指bit0~15，存放的是地址偏移量。"<<16"是指bit16~31，存放是當前EndPoint的FIFO的大小。
/**
* @brief Set Tx FIFO
* @param hpcd PCD handle
* @param fifo The number of Tx fifo
* @param size Fifo size
* @retval HAL status
*/
HAL_StatusTypeDef HAL_PCDEx_SetTxFiFo(PCD_HandleTypeDef *hpcd, uint8_t fifo, uint16_t size)
{
uint8_t i = 0;
uint32_t Tx_Offset = 0U;
/* TXn min size = 16 words. (n : Transmit FIFO index)
When a TxFIFO is not used, the Configuration should be as follows:
case 1 : n > m and Txn is not used (n,m : Transmit FIFO indexes)
--> Txm can use the space allocated for Txn.
case2 : n < m and Txn is not used (n,m : Transmit FIFO indexes)
--> Txn should be configured with the minimum space of 16 words
The FIFO is used optimally when used TxFIFOs are allocated in the top
of the FIFO.Ex: use EP1 and EP2 as IN instead of EP1 and EP3 as IN ones.
When DMA is used 3n * FIFO locations should be reserved for internal DMA registers */
//the RAM size that must be allocated to the RxFIFO.
Tx_Offset = hpcd->Instance->GRXFSIZ;
/*
DIEPTXF0_HNPTXFSIZ <=equivalent to DIEPTXF0=>
DEVICE MODE:
Bits 31:16 TX0FD: Endpoint 0 TxFIFO depth
This value is in terms of 32-bit words.
Minimum value is 16 Maximum value is 256
Bits 15:0 TX0FSA: Endpoint 0 transmit RAM start address
This field contains the memory start address for the endpoint 0 transmit FIFO RAM
DIEPTXFx
Bits 31:16 INEPTXFD: IN endpoint TxFIFO depth
This value is in terms of 32-bit words.
Minimum value is 16
The power-on reset value of this register is specified as the largest IN endpoint FIFO number depth.
Bits 15:0 INEPTXSA: IN endpoint FIFOx transmit RAM start address
This field contains the memory start address for IN endpoint transmit FIFOx. The address must be aligned with a 32-bit memory location.
*/
if(fifo == 0){
hpcd->Instance->DIEPTXF0_HNPTXFSIZ = (uint32_t)(((uint32_t)size << 16U) | Tx_Offset);
}
else
{
Tx_Offset += (hpcd->Instance->DIEPTXF0_HNPTXFSIZ) >> 16U;
for (i = 0; i < (fifo - 1); i++)
{
Tx_Offset += (hpcd->Instance->DIEPTXF[i] >> 16U);
}
/* Multiply Tx_Size by 2 to get higher performance */
hpcd->Instance->DIEPTXF[fifo - 1] = (uint32_t)(((uint32_t)size << 16U) | Tx_Offset);
}
return HAL_OK;
}