STM32F USB Firmware (cdc class driver) bug (64 byte transfers from device to host)

[mikael239955_stm1]

Posted on March 21, 2013 at 10:46

Hi,

64 byte transfers from my STM32F4 cdc driver to the host side fails. 63 bytes work, as well as 65 bytes. A quick forum search indicates that this is a bug in the cdc class driver firmware. A 64 byte transfer should be followed by a 0-byte transfer so that the host side (windows) can detect end of transfer. So, this bug is known but I have so far failed to find a fix for it. Does anyone know how to fix it - or is there a firmware library out there somewhere where this is fixed already? Currently I'm using ''STM32_USB-Host-Device_Lib_V2.1.0'', V1.1.0 / 19-March-2012 Best regards, Mikael

[tyronexj]

Posted on March 22, 2013 at 10:04

Hi Mikael,

I am working with USB VCP example recently. I am not sure whether following modification could fix the bug. /**   * @brief  Handle_USBAsynchXfer   *         Send data to USB   * @param  pdev: instance   * @retval None   */ static void Handle_USBAsynchXfer (void *pdev) {   uint16_t USB_Tx_ptr;   static uint16_t USB_Tx_length = 0;     if(USB_Tx_State != 1)   {     if (APP_Rx_ptr_out == APP_RX_DATA_SIZE)     {       APP_Rx_ptr_out = 0;     }          if(APP_Rx_ptr_out == APP_Rx_ptr_in)     {       if(USB_Tx_length == CDC_DATA_MAX_PACKET_SIZE)       {         USB_Tx_length = 0;       }       else       {         USB_Tx_length = 0;         USB_Tx_State = 0;         return;       }     }     else if(APP_Rx_ptr_out > APP_Rx_ptr_in) /* rollback */     {       APP_Rx_length = APP_RX_DATA_SIZE - APP_Rx_ptr_out;          }     else     {       APP_Rx_length = APP_Rx_ptr_in - APP_Rx_ptr_out;           } #ifdef USB_OTG_HS_INTERNAL_DMA_ENABLED      APP_Rx_length &= ~0x03; #endif /* USB_OTG_HS_INTERNAL_DMA_ENABLED */     if (APP_Rx_length > CDC_DATA_IN_PACKET_SIZE)     {       USB_Tx_ptr = APP_Rx_ptr_out;       USB_Tx_length = CDC_DATA_IN_PACKET_SIZE;              APP_Rx_ptr_out += CDC_DATA_IN_PACKET_SIZE;       APP_Rx_length -= CDC_DATA_IN_PACKET_SIZE;     }     else     {       USB_Tx_ptr = APP_Rx_ptr_out;       USB_Tx_length = APP_Rx_length;              APP_Rx_ptr_out += APP_Rx_length;       APP_Rx_length = 0;     }     USB_Tx_State = 1;     DCD_EP_Tx (pdev,                CDC_IN_EP,                (uint8_t*)&APP_Rx_Buffer[USB_Tx_ptr],                USB_Tx_length);   } } Best regards, Tyrone

[tyronexj]

Posted on March 22, 2013 at 10:58

Sorry,

usbd_cdc_DataIn() also calls DCD_EP_Tx(CDC_IN_EP), then static uint16_t USB_Tx_length = 0 should be seen in the whole file. Best regards, Tyrone