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https://github.com/thansen0/wiringbeaglelite

A self-contained interface for interacting with beaglebone GPIO pins
https://github.com/thansen0/wiringbeaglelite

Last synced: 30 days ago
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A self-contained interface for interacting with beaglebone GPIO pins

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README 

        
# WiringBeagle Lite



Despite its popularity and age, I wasn't able to find an easy to use GPIO or PWM library for the beaglebone that was updated for kernel 4.14, so wrote my own. This project is intended to be a stand-alone file and require no additional package installations other than default C.



## What this is



This library is meant to be reminiscent of Arduino GPIO and PWM interaction, meaning it has a pinMode(), digitalWrite(), and digitalRead() function. It's meant to be self-contained in a single .c and .h file, and it's meant to be easily modified if the user wants to add functionality or modify functionality in some way.



My goal with this code is just to save people the few hours it takes to learn what GPIO pins are and get them running, as well as make this familiar to people who have used Arduino in the past.



## What's coming/not implemented



PWM pin 42 uses some different hardward overlay than the rest of the pins, and it's not immediately apparent how that overlay works. The rest of the pins should work with any beaglebone using a kernel version after 4.14. I may add this pin at a later date however currently it's not implemented like the rest of the pins are.



## How to install it



There are no libraries to install, since this is just two files. Just add the files to your working directory and include the header `#include "wiringbeagle.h"` or `#include "src/wiringbeagle.h"` if you leave it in the /src folder. That should be it.



## How to use the GPIO pins



The libraries are set up the same as with Arduio. You need to initialize the pin with `pinMode(int pin, int mode)`, where `mode` is either `OUTPUT`, `INPUT`, or `UNEXPORT`. Each of these nodes initialize the GPIO pin and set the direction to their respective terms with the exception of `UNEXPORT`. This isn't available in arduino and it essentially turns off the pin and deletes the file structure. You don't have to do this after closing the program, since the OS will unexport them all when it reboots and there's nothing wrong with just leaving the pin unexported in the first place. If you don't know what it means to unexport it you probably don't have to worry about it.



After initializing the pin you can use `digitalWrite(int pin, short type)` to write either `HIGH` (1) or `LOW` (0) (for an OUTPUT pin) or use `digitalRead(int pin)` to read what the pin is reading, it returns the value in the value register for the pin.



There's an example in the example.c file and here's one in code:



```

#include  // for sleep function

#include "src/wiringbeagle.h" // if the .h and .c files are in the same folder no need for src/



int main() {



	int LED_pin = 67;



	pinMode(LED_pin, OUTPUT);



	while (true) {

		digitalWrite(LED_pin, HIGH);



		sleep(1);



		digitalWrite(LED_pin, LOW);



		sleep(1);

	}



}



```



## How to use the PWM pins (unfinished but may work for you)



The PWM pins also work in a similar manner to arduino boards. The user must export the pin first using `pinMode(pin, PWMOUTPUT)`, and then they may using `analogWrite(pin, duty_cycle)`, which has a period of 255.



There is a second function added, `analogWrite2(pin, period, duty\_cycle)` (named as such since basic C without C++ doesn't allow overloading) which allows you to set the period as well as duty\_cycle. Both return -1 if the function has an error.



```



int main() {



	int pwm_pin = 14;



	pinMode(pwm_pin, PWMOUTPUT);



	int er = analogWrite(pwm_pin, 127);



	if (er < 0) {

		printf("Unable to enable pwm pin %i\n", pwm_pin);

	}



}



```



## Troubleshooting the PWM pins



Most of the issues that come with the PWM pins is that depending on the version you get a different file path, and so far I'm not sure how to tell which is which. If you're having problems with the PWM functionality not working, you can check out [this guide](https://github.com/beagleboard/bb.org-overlays/blob/master/examples/cape-unversal-pwm.txt) and [this one](https://stackoverflow.com/questions/50203064/pwm-on-beaglebone-black-v4-14) which are effectively how I'm doing it in the code. You can simply check where your files are and changed the hardcoded file-urls.