-
- /* Read bytes from the USART receive buffer into the USB IN endpoint */
- while (USARTtoUSB_Buffer.Count)
- CDC_Device_SendByte(&VirtualSerial_CDC_Interface, RingBuffer_Remove(&USARTtoUSB_Buffer));
-
- /* Load bytes from the USART transmit buffer into the USART */
- while (USBtoUSART_Buffer.Count)
- Serial_TxByte(RingBuffer_Remove(&USBtoUSART_Buffer));
-
+
+ /* Check if the UART receive buffer flush timer has expired or the buffer is nearly full */
+ uint16_t BufferCount = RingBuffer_GetCount(&USARTtoUSB_Buffer);
+ if (BufferCount)
+ {
+ Endpoint_SelectEndpoint(VirtualSerial_CDC_Interface.Config.DataINEndpoint.Address);
+
+ /* Check if a packet is already enqueued to the host - if so, we shouldn't try to send more data
+ * until it completes as there is a chance nothing is listening and a lengthy timeout could occur */
+ if (Endpoint_IsINReady())
+ {
+ /* Never send more than one bank size less one byte to the host at a time, so that we don't block
+ * while a Zero Length Packet (ZLP) to terminate the transfer is sent if the host isn't listening */
+ uint8_t BytesToSend = MIN(BufferCount, (CDC_TXRX_EPSIZE - 1));
+
+ /* Read bytes from the USART receive buffer into the USB IN endpoint */
+ while (BytesToSend--)
+ {
+ /* Try to send the next byte of data to the host, abort if there is an error without dequeuing */
+ if (CDC_Device_SendByte(&VirtualSerial_CDC_Interface,
+ RingBuffer_Peek(&USARTtoUSB_Buffer)) != ENDPOINT_READYWAIT_NoError)
+ {
+ break;
+ }
+
+ /* Dequeue the already sent byte from the buffer now we have confirmed that no transmission error occurred */
+ RingBuffer_Remove(&USARTtoUSB_Buffer);
+ }
+ }
+ }
+
+ /* Load the next byte from the USART transmit buffer into the USART */
+ if (!(RingBuffer_IsEmpty(&USBtoUSART_Buffer)))
+ Serial_SendByte(RingBuffer_Remove(&USBtoUSART_Buffer));
+
projects / pub / USBasp.git / blobdiff