使用Node.js的Raspberry Pi 3 B型上的GPIO

Question

I am trying to blink the led using raspberry pi 3 model B,

I have all the required modules installed on my machine ie 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 ie 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