[sdiy] Rotary encoders: is there a clever way to handle many?

[Rick Jansen]

> On 11 Aug 2015, at 03:18, john slee <indigoid at oldcorollas.org> wrote:
> 
>> On 10 August 2015 at 21:45, Rick Jansen <rick.jansen at xs4all.nl> wrote:
>> It works quite well, but at the same time I wonder how other machines work, that track 8 or 16 rotary encoders.. An Arduino Mega has many more interrupt pins than the measly Arduino Uno, but still. Is there a clever trick to track many rotary encoders that I am missing?
> 
> Note that while the ATmega328 has two interrupt pins, it ALSO has a pin-change interrupt (PCINT) mechanism wherein you set a mask for the pins you want to monitor, and then it generates a PCINT interrupt when any of those pins change.
> 
> So you could add all your encoder GPIO pins to the mask and then whenever it fires, read all of them.
> 
> If you assign their GPIO pins sensibly you can then read 8 pins (one byte/four encoders) in one instruction.
> 
> John

Great idea! I had forgotten this is possible! It makes it easier to read at least a few encoders. Thanks!

rick
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