Taken from the sha204_library folder in
https://github.com/jimblom/sha204-Breakout
Commit 8e1ac05ef987b1869605ad067db2bdbaec1c109f
ATSHA204 is a crypto cirquit from Atmel that enables
SHA256-based MAC and HMAC calculations as well as
secure key storage and random number generation.
This can be used to sign messages passed between
sensor nodes and prevent both man-in-the-middle and
replay attacking.
This is a preparation for handling multiple interrupts in delay().
It also reduces the size of the interrupt-related variables and
arguments to int8_t as that should be ample enough for any Arduino
implementation.
The difference between the interrupt driven binary switch example and
the normal binary switch example is the following:
* Interrupt example does not use debouncer because it rely on loop()
iterating over time (but it sleeps between iterations)
* Interrupt example is more power conservative because it sleeps as soon
as it has sent updated data and no activity happens on the pin
* Interrupt example is limited to only two IO pins for the sensor, due
to limitations in the Arduino HW. The example uses the preprocessor to
ensure that this is not misconfigured or sleep function can not be
expected to behave as intended.
Patrick Fallberg