ozra / duino--holydio

PoC fast digital writes through compile time automatic coalescing of multiple pin writes when same port

HolyDio

Fastest and cleanest possible digital IO manipulation functions for *duino SBCs.

The libray is implemented header-only. I find that desirable!

There are several benefits of HolyDio compared to "fastDigitalWrite" and other similar libraries:

• HolyDio does not use polluting and dangerous macros. Instead it uses lex- and type-safe constexpr functions and templating (C++11/14).
• HolyDio composes multiple writes into one single register write automatically where possible! If you connect, say a stepper motor, on pins that reside on the same hardware port.
  • This gives us one, timing synced, operation totalling about 200 ns — in contrast to doing four individual writes totalling around 24,000 ns (!) with the standard arduino slowmo-lib.
  • Yes! It would take a hundred arduinos' combined processing power to get the same performance using stdlib functions! Suck on that.

Name

• Digital Input Output, and the rest obviously is a word play on the awesome 80's hit song / album.

Usage

• Add the lib to you project with: glue add HolyDio - or some other way (see "Installation")
• Include the library in you source: #include <HolyDio.h>

Performance

TODO profile for composite-set etc..

Stdlib digitalWrite on Arduino Uno 16MHz => 6280 ns HolyDio dioWrite => 125 ns.

Why make things fast fast?

• Your application might require it to meet a sufficient update rate
• Less wasted cycles is less wasted watts.
  • For a battery appliance, for instance, putting the SBC into low power sleep mode as soon, long and often as possible is desirable.
• The less energy we waste on earth, the more sustainable our future is.
• Making something absolutely fastest while being absolutely super simple to use is awesome coolest in my book (Yes, I do suffer iheavily from optimization syndrome — growing up with q <= 1MHz 8-bit machines).

Supported Hardware

• Arduino Due
• Arduino Zero
• Arduino Mega
• Arduino with ATmega644 or Atmega644P chip
• Arduino Leonardo
• Arduino Uno

If your SBC is not in the list, it will fail with a compile time error. Extending the library is very simple, so please take a stab at it and PR - I've littered the source code with comments, so it's a good exercise for the keen coder.

Installation

• Use glue package manager in your proj dir: glue add HolyDio
• Or simply git clone the repo in to your projects deps dir (if using build scripts - you should ;-) )
• Or git clone into arduino central libraries dir, if you use that hideous coding environment!

Reference

I've used arduino-stdlib/hardware/*/pins.h and Watterott's monolith bundle https://github.com/watterott/Arduino-Libs/tree/master/digitalWriteFast as references for pin-numbering and address-mapping.