blinking the raspi’s built-in LED

I’ve just added a repository of some JavaScript code to take over and exercise the built-in activity LED on a Raspberry Pi Zero W (and presumably other models). It’s called gpiozero-toggle-led and it’s a pretty simple interface with installation instructions and some sample code. It works with the underlying js-gpiozero JavaScript port of the popular original Python code. This would be an excellent way of simply demonstrating GPIO without any additional wiring, components, breadboards, extra power supplies or electrical knowledge (like finding a 330-ohm resistor using its color bands).

zero-wireless

Note that the “zero” in the title of the repository and in js-gpiozero does not refer to the Raspberry Pi Zero but to the original gpiozero Python library.

This should remove some of the guess work when attempting to use the relatively-new library since their documentation examples at the moment are taking a back seat to their code port from the more-extensive Python offering.

This approach can easily be modified to instead exercise external LEDs (as soldered or otherwise attached to the header pin locations seen below).  Note that you’ll use “BCM numbering” for APIs such as this one. For external LEDs, you would need to connect it inline with a resistor from a selected pin to one of the grounds for this to work with correct orientation of the LED’s anode/cathode, of course.

raspberry-pi-pinout

If you’re trying to use this with a Raspberry Pi of a different model, you’ll likely want to adjust the JavaScript slightly as seen below.

/routes/index.js:

// Existing code, for a Raspberry Pi Zero
var ledActivity = new LED(47, false);
// For Raspberry Pi 3, for example
var ledActivity = new LED(47);

And that’s it. Since the Raspberry Pi Zero assumes an opposite value for true/false than the bigger models, it’s necessary to configure this in the device constructor to make things work as expected. Since BCM pin 47 is the activity light on the board itself, this will allow you to control it.

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