Posted on January 23, 2016 at 19:05
* @file stm32f3xx_hal_pcd_ex.c
* @author MCD Application Team
* @version V1.2.0
* @date 13-November-2015
/**
* @brief Copy a buffer from user memory area to packet memory area (PMA)
* @param USBx: USB peripheral instance register address.
* @param pbUsrBuf: pointer to user memory area.
* @param wPMABufAddr: address into PMA.
* @param wNBytes: no. of bytes to be copied.
* @retval None
*/
void
PCD_WritePMA(USB_TypeDef *USBx, uint8_t *pbUsrBuf, uint16_t wPMABufAddr, uint16_t wNBytes)
{
uint32_t n = (wNBytes + 1) >> 1;
/* n = (wNBytes + 1) / 2 */
uint32_t i, temp1, temp2;
uint16_t *pdwVal;
pdwVal = (uint16_t *)(wPMABufAddr * 2 + (uint32_t)USBx + 0x400);
for
(i = n; i != 0; i--)
{
temp1 = (uint16_t) * pbUsrBuf;
pbUsrBuf++;
temp2 = temp1 | (uint16_t) * pbUsrBuf << 8;
*pdwVal++ = temp2;
pdwVal++;
pbUsrBuf++;
}
}
Probably this is most critical part for USB performance - data is moved from memory to PMA. Why bit arithmetic is here? What for so many useless variables are here?
my version(works fine)
void
PCD_WritePMA(USB_TypeDef *USBx, uint8_t *pbUsrBuf, uint16_t wPMABufAddr, uint16_t wNBytes)
{
int
n = (wNBytes + 1) >> 1;
// n = (wNBytes + 1) / 2
__IO uint32_t *pdwVal = (uint32_t *)(wPMABufAddr * 2 + (uint32_t)USBx + 0x400);
uint16_t * pwUsrBuf = (uint16_t *) pbUsrBuf;
for
(; n != 0; n--)
{
*pdwVal = *pwUsrBuf;
pwUsrBuf++;
pdwVal++;
}
}
