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Previously, the constants to use for the bit positions of the various UARTs were passed to the HardwareSerial constructor. However, this meant that whenever these values were used, the had to be indirectly loaded, resulting in extra code overhead. Additionally, since there is no instruction to shift a value by a variable amount, the 1 << x expressions (inside _BV and sbi() / cbi()) would be compiled as a loop instead of being evaluated at compiletime. Now, the HardwareSerial class always uses the constants for the bit positions of UART 0 (and some code is present to make sure these constants exist, even for targets that only have a single unnumbered UART or start at UART1). This was already done for the TXC0 constant, for some reason. For the actual register addresses, this approach does not work, since these are of course different between the different UARTs on a single chip. Of course, always using the UART 0 constants is only correct when the constants are actually identical for the different UARTs. It has been verified that this is currently the case for all targets supported by avr-gcc 4.7.2, and the code contains compile-time checks to verify this for the current target, in case a new target is added for which this does not hold. This verification was done using: for i in TXC RXEN TXEN RXCIE UDRIE U2X UPE; do echo $i; grep --no-filename -r "#define $i[0-9]\? " /usr/lib/avr/include/avr/io* | sed "s/#define $i[0-9]\?\s*\(\S\)\+\s*\(\/\*.*\*\/\)\?$/\1/" | sort | uniq ; done This command shows that the above constants are identical for all uarts on all platforms, except for TXC, which is sometimes 6 and sometimes 0. Further investigation shows that it is always 6, except in io90scr100.h, but that file defines TXC0 with value 6 for the UART and uses TXC with value 0 for some USB-related register. This commit reduces program size on the uno by around 120 bytes.
Arduino is an open-source physical computing platform based on a simple i/o board and a development environment that implements the Processing/Wiring language. Arduino can be used to develop stand-alone interactive objects or can be connected to software on your computer (e.g. Flash, Processing, MaxMSP). The boards can be assembled by hand or purchased preassembled; the open-source IDE can be downloaded for free. For more information, see the website at: http://www.arduino.cc/ or the forums at: http://arduino.cc/forum/ To report a *bug* in the software or to request *a simple enhancement* go to: http://github.com/arduino/Arduino/issues More complex requests and technical discussion should go on the Arduino Developers mailing list: https://groups.google.com/a/arduino.cc/forum/#!forum/developers If you're interested in modifying or extending the Arduino software, we strongly suggest discussing your ideas on the Developers mailing list *before* starting to work on them. That way you can coordinate with the Arduino Team and others, giving your work a higher chance of being integrated into the official release https://groups.google.com/a/arduino.cc/forum/#!forum/developers INSTALLATION Detailed instructions are in reference/Guide_Windows.html and reference/Guide_MacOSX.html. For Linux, see the Arduino playground: http://www.arduino.cc/playground/Learning/Linux CREDITS Arduino is an open source project, supported by many. The Arduino team is composed of Massimo Banzi, David Cuartielles, Tom Igoe, Gianluca Martino, Daniela Antonietti, and David A. Mellis. Arduino uses the GNU avr-gcc toolchain, avrdude, avr-libc, and code from Processing and Wiring. Icon and about image designed by ToDo: http://www.todo.to.it/