If the watchdog is enabled and bootscreen + SD card checks take too long, Marlin may hang at boot time because of the reset loop. We have this happen all the time with the Anet board if no SD card is inserted.
Replace all fastDigitalRead/Write() with READ/WRITE()
Define SCK_PIN, MISO_PIN, MOSI_PIN in pins.h if not already defined in the pins_*.h files.
Remove these conditional pin definitions from the pin-files. They are now always defined.
Define separate sets of SPI-pins for AT90USB with and without Teensy support in fastio.h.
Likely this was the main reason for all that confusion about the AT90USB-SPI pins.
- Add BIT and TEST macros
- Add _APPLY_ macros to stepper.cpp to help with consolidation
- Consolidate code in stepper.cpp using macros
- Apply standards in stepper.cpp
- Use >= 0 instead of > -1 as a better semantic
- Replace DUAL_Y_CARRIAGE with Y_DUAL_STEPPER_DRIVERS
