A library for simple Omega 2 GPIO management.
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A library for simple Omega 2 GPIO management.

What is this?

You can switch Omega 2 registers with the fast-gpio or gpiomux tool - but what if you wanted to do this not inside some bash script, but inside your own application?

Normally you would be condemned to use horrible things like system("fast-gpio blah blah"); - but it would be slow as duck (if we talk about something more than just switching led on and off).

It bothered me too - and so I've created my own small GPIO management library, basing on the official fast-gpio project from the Omega team (https://github.com/OnionIoT/fast-gpio).

How do I use this?

It's quite simple - just download the gpio.cpp and gpio.h, and include them in your code.

They export the Gpio class with following methods:

static void Gpio::initialize();

static void Gpio::pinMode(uint8_t pin, uint8_t direction);

static void Gpio::digitalWrite(uint8_t pin, uint8_t value);

static uint8_t Gpio::digitalRead(uint8_t pin);

static void Gpio::shiftOut(uint8_t dataPin, uint8_t clockPin, GpioBitOrder bitOrder, uint8_t value);

(you can find their descriptions inside the gpio.h: https://github.com/Patryk27/Omega2-GPIO/blob/master/gpio.h)

Can you show me any example, please?

Here ya go, pal: https://github.com/Patryk27/Omega2-GPIO/tree/master/examples

Why such a weird nomenclature?

I've based it on the Arduino standard library because most people familiar with electronics programming (including me) probably know that platform and there are many, many source codes on the web which use functions named like these - so it, theoretically, should be easier for us (the Omega programmers) to translate them from eg. Arduino/Raspberry to Omega, not having to think about "what and why the how is this command called here".

Although I have slightly modified it:

1.GPD_INPUT/GPD_OUTPUT instead of pure Arudino's INPUT/OUTPUT.

2.GPV_LOW/GPV_HIGH instead of just LOW/HIGH.

3.I've wrapped the functions in a class.

I did this because I don't feel like polluting the namespace is a convention worth following - and it does not hurt that much. You can always do #define INPUT GPD_INPUT or #define digitalWrite Gpio::digitalWrite if you feel like it.

Why your library lacks analogRead/analogWrite?

Omega 2 does not have any ADC (analog/digital converter) on the chip and so it is not possible to create any generic analogRead/analogWrite function.

If you want to use this, you'd have to buy some ADC and have fun on your own.

How do I compile this?

I am lazy and thus I didn't want to mess with any virtual machines just to compile a few small files - so I use my own Omega 2 to do the compiling.

And if you want too, you just have to:

1.Uncomment the LEDE repositories in /etc/opkg/distfeeds.conf (that is: reboot_core, reboot_base, reboot_luci and reboot_packages).

2.Do the opkg update && opkg install gcc (it will take a few minutes).

3.If everything went correctly, you should now be able to run gcc/g++ from the console (you can check it right now).

4.Assuming your gcc works - you can now without any problems compile applications on your Omega 2. Example command line can be:

g++ -std=c++11 gpio.cpp led-blink.cpp

It should take about 20 seconds and result in an a.out file (in the directory where you ran the command), which can be executed.

Disclaimer: I have tested it on my pivot-rooted Omega 2+ - I do not know if gcc works on the standard version (with the 64 MB of RAM) nor do I know if your Omega 2(+) without pivot-* will have sufficient storage space to install gcc.

Is your code tested?

I have succesfully written and operated a PCD8544 and PS2 mouse drivers (so far) using my methods so they should be pretty good. Although everything is eventually up to you - if you set two GPIOs to output and connect them, don't blame me if your Omega never wakes up.