Tag Archives: GPIO expander

Zero WH: pre-soldered headers and what to do with them

Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/zero-wh/

If you head over to the website of your favourite Raspberry Pi Approved Reseller today, you may find the new Zero WH available to purchase. But what it is? Why is it different, and what can you do with it?

Raspberry Pi Zero WH

“If you like pre-soldered headers, and getting caught in the rain…”

Raspberry Pi Zero WH

Imagine a Raspberry Pi Zero W. Now add a professionally soldered header. Boom, that’s the Raspberry Pi Zero WH! It’s your same great-tasting Pi, with a brand-new…crust? It’s perfect for everyone who doesn’t own a soldering iron or who wants the soldering legwork done for them.

What you can do with the Zero WH

What can’t you do? Am I right?! The small size of the Zero W makes it perfect for projects with minimal wiggle-room. In such projects, some people have no need for GPIO pins — they simply solder directly to the board. However, there are many instances where you do want a header on your Zero W, for example in order to easily take advantage of the GPIO expander tool for Debian Stretch on a PC or Mac.

GPIO expander in clubs and classrooms

As Ben Nuttall explains in his blog post on the topic:

[The GPIO expander tool] is a real game-changer for Raspberry Jams, Code Clubs, CoderDojos, and schools. You can live boot the Raspberry Pi Desktop OS from a USB stick, use Linux PCs, or even install [the Pi OS] on old computers. Then you have really simple access to physical computing without full Raspberry Pi setups, and with no SD cards to configure.

Using the GPIO expander with the Raspberry Pi Zero WH decreases the setup cost for anyone interested in trying out physical computing in the classroom or at home. (And once you’ve stuck your toes in, you’ll obviously fall in love and will soon find yourself with multiple Raspberry Pi models, HATs aplenty, and an area in your home dedicated to your new adventure in Raspberry Pi. Don’t say I didn’t warn you.)

Other uses for a Zero W with a header

The GPIO expander setup is just one of a multitude of uses for a Raspberry Pi Zero W with a header. You may want the header for prototyping before you commit to soldering wires directly to a board. Or you may have a temporary build in mind for your Zero W, in which case you won’t want to commit to soldering wires to the board at all.

Raspberry Pi Zero WH

Your use case may be something else entirely — tell us in the comments below how you’d utilise a pre-soldered Raspberry Pi Zero WH in your project. The best project idea will receive ten imaginary house points of absolutely no practical use, but immense emotional value. Decide amongst yourselves who you believe should win them — I’m going to go waste a few more hours playing SLUG!

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GPIO expander: access a Pi’s GPIO pins on your PC/Mac

Post Syndicated from Gordon Hollingworth original https://www.raspberrypi.org/blog/gpio-expander/

Use the GPIO pins of a Raspberry Pi Zero while running Debian Stretch on a PC or Mac with our new GPIO expander software! With this tool, you can easily access a Pi Zero’s GPIO pins from your x86 laptop without using SSH, and you can also take advantage of your x86 computer’s processing power in your physical computing projects.

A Raspberry Pi zero connected to a laptop - GPIO expander

What is this magic?

Running our x86 Stretch distribution on a PC or Mac, whether installed on the hard drive or as a live image, is a great way of taking advantage of a well controlled and simple Linux distribution without the need for a Raspberry Pi.

The downside of not using a Pi, however, is that there aren’t any GPIO pins with which your Scratch or Python programs could communicate. This is a shame, because it means you are limited in your physical computing projects.

I was thinking about this while playing around with the Pi Zero’s USB booting capabilities, having seen people employ the Linux gadget USB mode to use the Pi Zero as an Ethernet device. It struck me that, using the udev subsystem, we could create a simple GUI application that automatically pops up when you plug a Pi Zero into your computer’s USB port. Then the Pi Zero could be programmed to turn into an Ethernet-connected computer running pigpio to provide you with remote GPIO pins.

So we went ahead and built this GPIO expander application, and your PC or Mac can now have GPIO pins which are accessible through Scratch or the GPIO Zero Python library. Note that you can only use this tool to access the Pi Zero.

You can also install the application on the Raspberry Pi. Theoretically, you could connect a number of Pi Zeros to a single Pi and (without a USB hub) use a maximum of 140 pins! But I’ve not tested this — one for you, I think…

Making the GPIO expander work

If you’re using a PC or Mac and you haven’t set up x86 Debian Stretch yet, you’ll need to do that first. An easy way to do it is to download a copy of the Stretch release from this page and image it onto a USB stick. Boot from the USB stick (on most computers, you just need to press F10 during booting and select the stick when asked), and then run Stretch directly from the USB key. You can also install it to the hard drive, but be aware that installing it will overwrite anything that was on your hard drive before.

Whether on a Mac, PC, or Pi, boot through to the Stretch desktop, open a terminal window, and install the GPIO expander application:

sudo apt install usbbootgui

Next, plug in your Raspberry Pi Zero (don’t insert an SD card), and after a few seconds the GUI will appear.

A screenshot of the GPIO expander GUI

The Raspberry Pi USB programming GUI

Select GPIO expansion board and click OK. The Pi Zero will now be programmed as a locally connected Ethernet port (if you run ifconfig, you’ll see the new interface usb0 coming up).

What’s really cool about this is that your plugged-in Pi Zero is now running pigpio, which allows you to control its GPIOs through the network interface.

With Scratch 2

To utilise the pins with Scratch 2, just click on the start bar and select Programming > Scratch 2.

In Scratch, click on More Blocks, select Add an Extension, and then click Pi GPIO.

Two new blocks will be added: the first is used to set the output pin, the second is used to get the pin value (it is true if the pin is read high).

This a simple application using a Pibrella I had hanging around:

A screenshot of a Scratch 2 program - GPIO expander

With Python

This is a Python example using the GPIO Zero library to flash an LED:

[email protected]:~ $ export GPIOZERO_PIN_FACTORY=pigpio
[email protected]:~ $ export PIGPIO_ADDR=fe80::1%usb0
[email protected]:~ $ python3
>>> from gpiozero import LED
>>> led = LED(17)
>>> led.blink()
A Raspberry Pi zero connected to a laptop - GPIO expander

The pinout command line tool is your friend

Note that in the code above the IP address of the Pi Zero is an IPv6 address and is shortened to fe80::1%usb0, where usb0 is the network interface created by the first Pi Zero.

With pigs directly

Another option you have is to use the pigpio library and the pigs application and redirect the output to the Pi Zero network port running IPv6. To do this, you’ll first need to set some environment variable for the redirection:

[email protected]:~ $ export PIGPIO_ADDR=fe80::1%usb0
[email protected]:~ $ pigs bc2 0x8000
[email protected]:~ $ pigs bs2 0x8000

With the commands above, you should be able to flash the LED on the Pi Zero.

The secret sauce

I know there’ll be some people out there who would be interested in how we put this together. And I’m sure many people are interested in the ‘buildroot’ we created to run on the Pi Zero — after all, there are lots of things you can create if you’ve got a Pi Zero on the end of a piece of IPv6 string! For a closer look, find the build scripts for the GPIO expander here and the source code for the USB boot GUI here.

And be sure to share your projects built with the GPIO expander by tagging us on social media or posting links in the comments!

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