https://forum.pjrc.com/threads/41282-Strange-looking-limit-checks-in-Teensy3-Version-of-Stream-cpp

https://forum.pjrc.com/threads/40893-Incorrect-return-for-Serial-write()-on-Teensy-3-6?p=127732#post127732

I'm not sure if this fix has some side-effects - how will other functions react when it does not return zero anymore ?

https://forum.pjrc.com/threads/40893-Incorrect-return-for-Serial-write()-on-Teensy-3-6?p=127764&viewfull=1#post127764

AudioStream.h: Allow inclusion from assembler .S files

Additional PR for SERIALX_DISABLE follows

The spaces after TOOLSPATH will append to the variable value. Merged the on Linux comment with previous comment to fix.

Earlier I had pin 20 as the default SCK1, but card shows that pin 32 is
the default pin

close hole for race condition

Has to add core_pins.h to get delayMicroseconds()
made empty while()'s on HSRUN state change have a measurable 2us wait
each iteration
added explicit 100us delay leaving HSRUN to allow internal V to
satbilize, seems CPU does this already as 10-50 us made no change, and
100 is not measurable on larger writes.
since eeprom_initialize() blindly restores interrupts amd can run under
HSRUN, moved hsrun_off()

EEPROM write on T_3.6 under HSRUN - Drop and Raise

https://forum.pjrc.com/threads/34808-K66-Beta-Test?p=116690&viewfull=1#post116690

Results in valid serial # presented to USB host when T_3.6 is in HSRUN mode.

Added in the additional SPI pins
MISO 39
MOSI 28
SCK 27

Tested with my ILI9341_t3n (SPIN) version.  Will also
Add to ILI9341_t3.