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Arduino IDE 1.x
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How does a library module determine the hardware #6087

Closed rrvt closed 7 years ago

rrvt commented 7 years ago

How does a library determine the hardware being used. By this I mean the processor and the Arduino/Other board. If one chooses to develop a library that writes things close to the hardware it is essential that the correspondence between chip registers and the external pins on the board be known at compile time so that different choices may be made at compile time.

An ino file is compiled with one of the following identifiers defined: AVR_ATmega328p AVR_ATmega168 AVR_ATmega1280 AVR_ATmega2560 AVR_ATmega32u4 AVR_ATtiny85

Would it be possible to do the same for the library files?

It probably would be useful to also define an identifier for the specific board also so that mappings between the internal registers and external pins could be defined...

facchinm commented 7 years ago

Sure, you can write processor-specific code by enclosing the relevant bits between ifdefs as described here: http://www.atmel.com/webdoc/avrlibcreferencemanual/using_tools_1using_avr_gcc_mach_opt.html

For example, a piece of code specific for the UNO will look like

#ifdef __AVR_ATmega328P__
...code here
#endif
cmaglie commented 7 years ago

There are also a specific define per-board, for example the Arduino Leonardo has:

ARDUINO_AVR_LEONARDO
ARDUINO_ARCH_AVR

you can quickly find them if you enable "verbose compile" on the preferences:

     [exec] "/home/cmaglie/Code/arduino/build/linux/work/hardware/tools/avr/bin/avr-g++"
-c -g -Os -Wall -Wextra -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections
-fno-threadsafe-statics -MMD -flto -mmcu=atmega32u4 -DF_CPU=16000000L -DARDUINO=10802
-DARDUINO_AVR_LEONARDO -DARDUINO_ARCH_AVR     <-----
-DUSB_VID=0x2341 -DUSB_PID=0x8036 '-DUSB_MANUFACTURER="Unknown"'
'-DUSB_PRODUCT="Arduino Leonardo"'
"-I/home/cmaglie/Code/arduino/build/linux/work/hardware/arduino/avr/cores/arduino"
"-I/home/cmaglie/Code/arduino/build/linux/work/hardware/arduino/avr/variants/leonardo"
"/home/cmaglie/Code/arduino/build/linux/work/hardware/arduino/avr/cores/arduino/main.cpp"
-o "/tmp/arduino_build_72059/core/main.cpp.o"
rrvt commented 7 years ago

Both solutions work, thanks. Bob