I did some performance testing.

The Pro Micro runs an Atmel 32u4 at 8MHz.
If the code does nothing else,
I was able to poll all pins around 13 times every 1ms,
or 13kHz.


Sample Rate
-----------

The number of samples taken since the last HID report
is sent as the second Y axis.
If you use the 
[included gamepad tester](gamepad.html),
it will show the approximate number of samples as an integer,
for Y axis 2.

This is approximate,
because the browser encodes the value as a real number between -1 and 1.
We convert it back, but may lose a little precision.
It's close enough for me,
hopefully it's close enough for you.


Debouncing
----------

Using `millis()` time to debounce the switch
roughly halved my sample frequency.
So instead, I do some preprocessor arithmetic
to calculate how many samples to take after an edge,
in order to debounce switches.

The drum controller was a partcular pain:
in addition to the switch bouncing,
the stick was bouncing on the rubber pad.
I settled on a 40ms silence window as feeling pretty good.
You can adjust this if you want to.


Gamepad Buttons
---------------

The `buttons` struct member is a bitmap,
each bit mapping to one of the 12 buttons reported through HID.
Here's what each bit means:

*  0: Blue
*  1: Green
*  2: Red
*  3: Yellow
*  4: Orange
*  5: Tilt Switch / 2x kick
*  6: Solo modifier (second row of buttons on guitar)
*  7: ?
*  8: Minus
*  9: Plus
* 10: Drum pad modifier?
* 11: Cymbal modifier?
* 12: ?


hatAndConstant
--------------

I don't get this, but here's what the values mean:

* 2: right
* 6: left
* 0: up
* 4: down
* 8: nothing