Serial_::operator bool()
{
bool result = false;
if(USBDevice.configured()
&& (_cdcLineState & CONTROL_LINE_STATE_DTR)
&& !USB_IsSendQFull(CDC_TX)
// && !USB_IsStalled(CDC_TX)
)
{
result = true;
}
// We add a short delay before returning to fix a bug observed by Federico
// where the port is configured (_cdcLineState != 0) but not quite opened.
// delay(10);
if(!result)
{
if(!USBDevice.configured())
{
#ifdef DEBUG_CODE
error_printP(F("USB device not configured"));
#endif // DEBUG_CODE
}
else if(!(_cdcLineState & CONTROL_LINE_STATE_DTR))
{
#ifdef DEBUG_CODE
error_printP(F("DTR is off"));
#endif // DEBUG_CODE
}
else if(USB_IsSendQFull(CDC_TX))
{
#ifdef DEBUG_CODE
error_printP(F("Send Queue FULL"));
#endif // DEBUG_CODE
}
// else if(USB_IsStalled(CDC_TX))
// {
//#ifdef DEBUG_CODE
// error_printP(F("USB is stalled"));
//#endif // DEBUG_CODE
// }
}
return result;
}
size_t Serial_::write(const uint8_t *buffer, size_t size)
{
/* only try to send bytes if the high-level CDC connection itself
is open (not just the pipe) - the OS should set _cdcLineState when the port
is opened and clear _cdcLineState when the port is closed.
bytes sent before the user opens the connection or after
the connection is closed are lost - just like with a UART. */
// NOTE: if my outgoing buffer is too full, stop sending
// TODO - ZE - check behavior on different OSes and test what happens if an
// open connection isn't broken cleanly (cable is yanked out, host dies
// or locks up, or host virtual serial port hangs)
if(USBDevice.configured() && // make sure I'm running
// !USB_IsStalled(CDC_TX) && // make sure I'm not stalled
!USB_IsSendQFull(CDC_TX)) // make sure I'm not flooding the queue
{
if(_cdcLineState & CONTROL_LINE_STATE_DTR) // make sure DTR is set
{
if(size > 128)
{
size = 128; // adjust size DOWN to limit output buffer size
}
int r = USB_Send(CDC_TX, buffer, size, 1);
// TODO: check for partial sends and retry??
if(r > 0)
{
CDC_FrameReceived(); // inform the host of my data send/receive state
return r;
}
}
}
// TODO: block?
setWriteError();
return 0;
}
