HAL_PCDEx_SetRxFiFo 和 HAL_PCDEx_SetTxFiFo
这两个函数的作用是：该EndPoint数据传输最大数量的限定
除前面贴子里廛的影响数据传输量的函数外，这两个HAL_PCDEx_SetRxFiFo / HAL_PCDEx_SetTxFiFo函数也值得注意。
其一，这两个函数是有使用顺序的（参考USBD_LL_Init函数）：HAL_PCDEx_SetRxFiFo先设置GRXFSIZ，然后HAL_PCDEx_SetTxFiFo中会用到这个GRXFSIZ。
另外，所有EP共享的Rx FIFO + 所有的Tx FIFO，最大允许在RAM中开辟的空间为1.25kB（i.e. max. 0x140 words）
下面的代码中，Tx_Offset是指bit0~15，存放的是地址偏移量。"<<16"是指bit16~31，存放是当前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 wordsThe 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 depthThis value is in terms of 32-bit words.Minimum value is 16 Maximum value is 256Bits 15:0 TX0FSA: Endpoint 0 transmit RAM start addressThis field contains the memory start address for the endpoint 0 transmit FIFO RAMDIEPTXFxBits 31:16 INEPTXFD: IN endpoint TxFIFO depthThis 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 addressThis 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;
}