rpi-gpio module works in Node shell but not through code

Question

I've setup my Raspberry Pi 2 Model B v1.1 with Node.js v8.7 and installed the rpi-gpio module.

I used Node shell (REPL) to test the module, and it worked like a charm. But when I put the same 3 lines of code in app.js and try a node app.js I get the following error. Code added below for reference.

Error:

/home/pi/PiClient/node_modules/rpi-gpio/rpi-gpio.js:358
        return currentPins[channel] + '';
                          ^

TypeError: Cannot read property '7' of undefined
    at getPinRpi (/home/pi/PiClient/node_modules/rpi-gpio/rpi-gpio.js:358:27)
    at Gpio.read.input (/home/pi/PiClient/node_modules/rpi-gpio/rpi-gpio.js:266:19)
    at Object.<anonymous> (/home/pi/PiClient/test.js:5:6)
    at Module._compile (module.js:624:30)
    at Object.Module._extensions..js (module.js:635:10)
    at Module.load (module.js:545:32)
    at tryModuleLoad (module.js:508:12)
    at Function.Module._load (module.js:500:3)
    at Function.Module.runMain (module.js:665:10)
    at startup (bootstrap_node.js:187:16)

Code:

var gpio = require('rpi-gpio');
gpio.(7, gpio.DIR_IN);
gpio.read(7, function (err, val) {
   console.log(err, val);
});

Quintin B · Accepted Answer · 2017-10-19 07:14:31Z

1

Looking at the documentation and your code it looks like you may not have called the SETUP method correctly:

var gpio = require('rpi-gpio');

gpio.setup(7, gpio.DIR_IN, readInput);

function readInput() {
    gpio.read(7, function(err, value) {
        console.log('The value is ' + value);
    });
}

Looking at your code the second line is:

gpio.(7, gpio.DIR_IN);

which looks to me like you are missing the method name after the first '.'

answered Oct 19, 2017 at 7:14

Quintin B

6891 gold badge5 silver badges20 bronze badges

Damn. I thought the callback was optional. I'm still looking into why it worked in REPL.

Omkar Khair
– Omkar Khair

2017-10-19 07:41:49 +00:00
Commented Oct 19, 2017 at 7:41
1

This explains. github.com/JamesBarwell/rpi-gpio.js/issues/72#event-1300520932

Omkar Khair
– Omkar Khair

2017-10-19 07:43:26 +00:00
Commented Oct 19, 2017 at 7:43
1

Great! Glad we are learning!

Quintin B
– Quintin B

2017-10-19 07:44:07 +00:00
Commented Oct 19, 2017 at 7:44

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