AVRFreaks.net

void device_cdc_task_init(void) {
  sof_cnt   = 0;
  Usb_enable_sof_interrupt();
}

void usb_set_configuration_action(void) {
   Usb_enable_endpoint_bank_autoswitch(TX_EP);
}

void usb_sof_action(void) {
  sof_cnt++;
}

   if (sof_cnt >= NB_MS_BEFORE_FLUSH) { //Flush buffer in Timeout
      sof_cnt = 0;
      if( 0 == Usb_nb_busy_bank(TX_EP) ) {
         Usb_ack_in_ready_send(TX_EP);
      }         
   }

typedef struct {
   unsigned long int nextDescriptorAddress __attribute__ ((aligned (32)));
   unsigned long int HSBAddress __attribute__ ((packed));
   unsigned long int control __attribute__ ((packed));
}TransferDescriptor;

   replyTransferDescriptor.nextDescriptorAddress = (unsigned long int)NULL;
   replyTransferDescriptor.HSBAddress = 0;
   replyTransferDescriptor.control = 0;

void sendMessage(void *txbuf, int messageLenght) {
   replyTransferDescriptor.HSBAddress = (unsigned long int)txbuf;   
   replyTransferDescriptor.control = ((messageLenght) << 16) | AVR32_USBB_UXDMAX_CONTROL_DMAEND_EN_MASK | AVR32_USBB_UXDMAX_CONTROL_BUFF_CLOSE_IN_EN_MASK |  AVR32_USBB_UXDMAX_CONTROL_CH_EN_MASK;   
   AVR32_USBB_UDDMAX_nextdesc(TX_EP) = (unsigned long int)&replyTransferDescriptor.nextDescriptorAddress; // Point at transfer descriptor
   AVR32_USBB_UDDMAX_control(TX_EP) =  AVR32_USBB_UXDMAX_CONTROL_LD_NXT_CH_DESC_EN_MASK; // Load that transfer descriptor

   LED_On(LED0);
   while ( (AVR32_USBB_UDDMAX_status(TX_EP) && AVR32_USBB_UXDMAX_STATUS_CH_EN_MASK) == 1 ) { // AVR32_USBB_UXDMAX_STATUS_CH_EN_MASK
      LED_On(LED0);
   };
   LED_Off(LED0);

   sof_cnt = 0;
   Usb_ack_in_ready_send(TX_EP);
}