Updated (10/10/20 v6.3.9)
Updated T4 SPI driver.
Changed Button Hold example pin to 6.
Updated start early hook in T4.

><b>Updated (4/20/20 v6.3.8)</b><br>
* Maintenance release.<br>
* Added new examples.<br>
* Fixed all sketchs to work now, hopefully:).<br>
* Teensy 4.0 should work now, many fixes.<br>
* More code clean ups.<br>

><b>Updated (4/15/20 v6.3.7)</b><br>
* Maintenance release.<br>
* Added v1 Teensy 4.0 support.<br>
* Updated and fixed examples.<br>
* Updated docs.<br>

><b>Updated (2/9/20 v6.3.6)</b><br>
* Maintenance release.<br>
* Fixed Digital driver pin type to HAL.<br>
* Snooze "sleep" now works for most drivers.<br>
* Added Touch support for T-LC/36 Snooze "sleep" now!<br>
* New function to change between LLS and VLLS modes in "deepSleep and hibernate".<br>
* Wakeup ISR now run fastrun section for T3.x.<br>
* Removed dummy Drivers, now will give an error if tried to use.<br>
* Got rid of Drivers "isr" function, not needed since all "sleep" interrupt's run through the hal now.<br>
* Changed "type" param to "mode" to not confict with pin type, i.e. "RISING,FALLING,etc...".<br>


><b>Updated (2/5/20 v6.3.5)</b><br>
* Maintenance release.<br>
* Uncoupled Snooze Class from drivers.<br>
* Only deepSleep and hibernate work so far.<br>
* Only LLS sleep mode for now.<br>
* Checked all wakeups for TLC and 3.x.<br>
* Hopefully improved wakeup sequence.<br>

><b>Updated (12/9/18 v6.3.4)</b><br>
* Fixed sleep wake souce reporting.<br>
* sleep compare now works.<br>
* add more comments.<br>

><b>Updated (11/20/18 v6.3.3)</b><br>
* Added F_CPU 256MHz.<br>

><b>Updated (11/4/17 v6.3.2)</b><br>
* TeensyLC SnoozeSleepPWM example now works.<br>
* Warning: now TeensyLC Internal Ref Clock is enabled, might lead to higher sleep currents.<br>

><b>Updated (9/5/17 v6.3.1)</b><br>
* Fixed compare for TeensyLC<br>
* Removed Wire library include from SnoozeAudio<br>

><b>Updated (8/30/17 v6.3.0)</b><br>
* Fixed examples "compare driver", thanks Erik-k -> https://github.com/Erik-k.<br>
* Audio Driver for ADC, DAC, STGL5000.<br>
* add SPI Driver.<br>
* added clock transistion -> pee_bple and blpe_pee.<br>
* fixed VLLS3-1, was only using VLLS3.<br>
* alarm driver function name change.<br>
* fixed actual Compare Driver, added pins 9 and 4, pin 12 is not a valid pin.<br>

><b>Updated (3/27/17 v6.2.9)</b><br>
* Fixed USB Serial driver for none USB_SERIAL type.<br>
* Fixed return clock from sleep mode at 24MHz.<br>
* Fixed typo in sleep_usb_serial.ino example.<br>

><b>Updated (2/20/17 v6.2.8)</b><br>
* Re-added support for Teensy 3.0.<br>

><b>Updated (2/16/17 v6.2.7)</b><br>
* Fixed sleep functions not returning right wakeup values.<br>
* Updated examples.<br>
* Added Teensy LC LED buffer driver.<br>
* Usb works better now not perfect though.<br>

><b>Updated (1/31/17 v6.2.6)</b><br>
* Fixed T3.6 High Speed Run deepSleep and hibernate.<br>
* Timer driver only uses the LPO clock.<br>

><b>Updated (1/4/17 v6.2.5)</b><br>
* Added Serial USB Driver.<br>
* Added PWM Sleep Driver example.<br>

><b>Updated (10/18/16 v6.2.4)</b><br>
* Fix bug with Teensy LC digital driver.<br>
* Update README.md links.<br>

><b>Updated (10/18/16 v6.2.3)</b><br>
* Temp fix for Teensy LC Timer driver below 50ms.<br>

><b>Updated (10/18/16 v6.2.2)</b><br>
* Temp fix for Teensy error when not using RTC Library.<br>
* Now hibernate and deepsleep work from a isr.<br>
* Fix warnings from SnoozeCompare driver.<br>

><b>Updated (9/19/16 v6.2.1)</b><br>
* Merge fix for core Digital wakeup from Github user jymoulin.<br>

><b>Updated (9/6/16 v6.2.0)</b><br>
* Teensy35/36 now complies, need more testing for actual usage.<br>

><b>Updated (8/31/16 v6.1.1)</b><br>
* Fixed skelton class example.<br>

><b>Updated (8/30/16 v6.1.0)</b><br>
* Add INPUT_PULLDOWN code.<br>

><b>Updated (7/12/16 v6.0.3)</b><br>
* Update License.<br>
* Fix core millis count for low power timer wakeup.<br>
* Add driver for Audio Library.<br>

><b>Updated (7/11/16 v6.0.2)</b><br>
* Teensy LC now compiles.<br>

><b>Updated (6/29/16 v6.0.1)</b><br>
* Initial Teensy 3.5 support.<br>
* Fixed Touch and Compare modules for Teensy LC.<br>

><b>Updated (4/20/16 v6.0.0)</b><br>
* New API.<br>

><b>Updated (1/12/16 v5.0.1)</b><br>
* Fix for new Teensy Reg Defs.<br>

><b>Updated (10/27/15 v5.0.0)</b><br>
* Now CPU Scaling is supported by the REDUCED_CPU_BLOCK macro.<br>
* Reset systick when cpu goes to 2 MHz.<br>

><b>Updated (9/30/15 v5.4.2)</b><br>
* Fixed Compiling TeensyLC PDB register in peripheral.h.<br>
* Fixed TeensyLC warnings.<br>

><b>Updated (9/7/15 v5.4.1)</b><br>
* Removed debug stuff.<br>
* Fixed Properites Catagory warning.<br>

><b>Updated (6/4/15 v5.4)</b><br>
* Made setTimer "time" param uint16_t.<br>
* Fixed sleep function tsi wakeup for Teensy LC, Teensy 3.x not working yet maybe never.<br>
* Removed unused code.<br>

><b>Updated (5/31/15 v5.3)</b><br>
* Fixed sleep function low power timer.<br>
* Fixed digital pin wake on LOW or HIGH interrupt type, now if pin interrupt type is configured LOW and the pin is LOW when going into sleep it will wake immediately, the same goes for if it is HIGH interrupt type.<br>

><b>Updated (5/28/15 v5.2.1)</b><br>
* Remove debug stuff.<br>

><b>Updated (5/19/15 v5.2)</b><br>
* Better documentation now but still needs work.<br>
* Fixed TSI wakeup number for sleep interrupts.<br>
* Digital Pins configurations only now change interrupt vector for the selected pin for the sleep function. This was do to Adafruit_nRF8001 library needing to keep its interrupt config intact. Possible problems still exists if a SnoozeBlock pin shares the same vector as the library or user code, not really sure how to handle that.
* Fixed LPTMR not resseting its compare time if other wakeup interrupt came before it. This would make the LPTMR not wait the full param time to fire its interrupt in next sleep mode.
* All library interrupts priorities raised to (current - 16) and LLWU priority raised to 32 because calling a function from an isr will block a lower priority interrupt.

><b>Updated (4/24/15 v5.1)</b><br>
* Fixed bug in Hibernate not giving the right wake up source and stopped setting unused registers in LLWU irq, Thanks to https://forum.pjrc.com/members/39437-rhubley.
* Functions sleep, deepSleep and hibernate now return wake source.
* Code cleanup and various code refactoring.
* Added library properties.
* Now compatible with Teensyduino 1.22.

><b>Updated (3/12/15)</b><br>
* Fixed again setting digital pin for Teensy-3.x/LC.
* Teensy LC pin 17 is set automatically to OUTPUT->LOW to reduce power.
* Now TSI work with Teensy-LC for deepSleep and hibernate.
* Compare some what works for Teensy-LC but will further modified in next release.
* Examples now are now Teensy-LC compatible.

><b>Updated (3/9/15)</b><br>
* Fixed setting digital pin for Teensy LC.
* Also need to set Teensy LC pin 17 to OUTPUT->HIGH.

><b>Updated</b><br>
* Initial TeensyLC support, not all wakeup sources are available, RTC, TSI, CMP and some digital pins are not waking the LC up either.

<h3>Initial Release:</h3>
1.  Trimmed down and simplified, tried to mimic standard Arduino conventions for setting wakeup pins etc..<br>
2.  Since Teensyduino now can be programed at many different CPU speeds, dynamically changing cpu speeds is no longer supported, maybe in future I can bring it back if wanted.<br>
3.  Now the teensy can sleep at ~10uA with hibernate function. Special care is need when using this function. Must uncomment the define statement to use.<br>
4.  All sleep mode work the same with regards to setting up wakeup events. A separate class (SnoozeBlock) holds all configurations similar to LowPower_Teensy3's sleepBlock but I hope better and easier to implement.<br>
