GPIO over Raspberry Pi 3 model B using Node.js - node.js

Question

I am trying to blink the led using raspberry pi 3 model B,
I have all the required modules installed on my machine i.e. npm , nodejs , pi-gpio (fixed the minor changes to detect the gpio )
Code is :
var gpio = require("pi-gpio");
gpio.open(16, "output", function(err) {
gpio.write(16, 1, function() {
gpio.close(16);
});
});
//reading the data on the pin i.e pin : 16
gpio.open(16, "output", function (err) {
gpio.read(16, function (err, value) {
console.log("Data is "+ value);
gpio.close(16);
});
});
But above code throws error while running it,
node app.js
error :
Error when trying to open pin 16
gpio-admin : could not flush data to /sys/class/gpio/export : Device or resource busy
Thanks in advance
Any links where I can see the circuit diagram and code.
Concern : I dont want to change the platform i.e. node.js
pi-gpio which i am using is : https://github.com/rakeshpai/pi-gpio

Answer 1

pi-gpio is just writing to the GPIO device in the background so you can skip node.js and pi-gpio and do the same manually for testing purposes.
Example:
gpio.open(16, ...
# is the same as writing in terminal:
echo 16 > /sys/class/gpio/export
and
... "output" ...
# is the same as writing in terminal:
echo "out" > /sys/class/gpio/gpio16/direction
etc.
First of all, try rebooting the Pi and see if that takes care of the issue.
If that didn't help, try manually closing/unexporting the pin as root and then re-run the script.
# unexport the pin as root in case something's holding on to it
sudo echo 16 > /sys/class/gpio/unexport
The commands below basically constitute the pi-gpio API. These lines are what you would put in a shell script to control your GPIOs. Test them without sudo first in the order I've written them and if they don't work, try with sudo. If they still don't work, I think you have a wiring/hardware problem or need to change some system settings elsewhere.
# unexport the pin
sudo echo 16 > /sys/class/gpio/unexport
# export it again
sudo echo 16 > /sys/class/gpio/export
# make it an output
sudo echo "out" > /sys/class/gpio/gpio16/direction
# write a HIGH - is the LED on now?
sudo echo 1 > /sys/class/gpio/gpio16/value
# read the value of the pin - is it 1 after writing a 1 to the pin?
cat /sys/class/gpio/gpio16/value
# write a LOW - did it turn off?
sudo echo 0 > /sys/class/gpio/gpio16/value

Answer 2

Let's use 'rpio' module instead of 'pi-gpio'.
https://github.com/jperkin/node-rpio
It works fine on Pi3, zero etc.

Answer 3

As pi-gpio has already fixed the old and new sysPath (issue# https://github.com/rakeshpai/pi-gpio )
But it is dependent on quick2wire-gpio-admin lib.
So small fix required in quick2wire-gpio-admin
git clone https://github.com/quick2wire/quick2wire-gpio-admin.git
cd quick2wire-gpio-admin
The src/gpio-admin.c has
int size = snprintf(path, PATH_MAX, "/sys/devices/virtual/gpio/gpio%u/%s", pin, filename);
replace with :
int size = snprintf(path, PATH_MAX, GPIO_CLASS_PATH "gpio%u/%s", pin, filename);
Then go to cd quick2wire-gpio-admin directory
Then sudo make uninstall and
sudo make install
Then it is running fine.
The Code for is as follows : (filename : blinking12.js)
var gpio = require("pi-gpio");
var intervalId;
var durationId;
var gpioPin = 12;
gpio.open(gpioPin, "output", function (err) {
var on =1 ;
console.log("GPIO pin "+gpioPin+" is open toggling LED every 100mS for 10s");
intervalId = setInterval( function () {
gpio.write(gpioPin, on, function () {
on = (on + 1)% 2;
});
}, 100);
});
durationId = setTimeout (function () {
clearInterval(intervalId);
clearTimeout(durationId);
console.log('10 seconds blinking completed');
gpio.write(gpioPin, 0, function () {
gpio.close(gpioPin);
//process.exit(0);
});
}, 10000);
To run the code :
node blinking12.js
Output on my machine :
GPIO pin 12 is open toggling LED every 100mS for 10s
10 seconds blinking completed