According to #3786 removed the reference to Leonardo only in while(!Serial) of the examples.
Changed in in "wait for serial port to connect. Needed for native USB port only"
Print::write(const uint8_t *buffer, size_t size) and Print::print(const
__FlashStringHelper *ifsh) would continue calling write(char) after a
failed write(char) this behavior would render returned count unuseable
see arduino/Arduino issue #3614
This makes the CDC "Serial" object on the Leonardo and similar boards
support this recently introduced method as well. The CDC code in the sam
core is not changed.
end() already waited for the buffer to be empty, but then there could
still be two bytes in the hardware registers that still need to be
transmitted (which were dropped or kept in the buffer, depending on the
exact timing).
This changes the wait loop to a call to the flush() function, which
already takes care of really waiting for all bytes to be transmitted,
meaning it is safe to turn off the transmitter.
This allows detecting when the USB host sends a break request and what
the value of the request was. See the comments in USBAPI.h for details.
This just modifies the avr core, not the sam core.
This allows a sketch to find out the settings chosen by the USB host
(computer) and act accordingly.
Other than reading the DTR flag and checking if the baudrate is 1200,
the regular CDC code doesn't actually use any of these settings.
By exposing these settings to the sketch, it can for example copy them
to the hardware UART, turning the Leonardo into a proper USB-to-serial
device. This can be useful to let the computer directly talk to whatever
device is connected to the hardware serial port (like an XBee module).
The Teensy core already supported these methods. This code was
independently developed, but the method names were chosen to match the
Teensy code, for compatibility (except that `dtr()` and `rtr()` return
`bool`, while the Teensy version return a `uint8_t`).
This change is applied to both the avr and sam cores, which have a very
similar CDC implementation.
