A short introductory Raspberry Pi Presentation for Santa Cruz PyLadies

I had mentioned a Raspberry Pi project at a Santa Cruz PyLadies meetup, and some people who weren't familiar with the Raspberry Pi asked me about it. I volunteered to demonstrate some Raspberry Pi stuff at the June 4, 2018 Speaker Night, and the following is the script I wrote for my presentation, with links and code.

Introduction to the Raspberry Pi

(I hand someone my Raspberry Pi, so they can examine it and pass it around the room.)

The Raspberry Pi is a single-board Linux computer which was first released in 2012, and over 19 million of them have been sold. The most common models are the size of a credit card, and cost around $35, but there are also smaller Raspberry Pi Zero models that only cost $5 and $10. You can use them as general purpose computers -- Idea Fab Labs has some as dedicated print servers for 3D printers -- but at those prices, as you can imagine they're pretty low-end and slow compared to mass-market laptop and desktop computers. What makes them particularly special and popular (in addition to the price) is that they have a lot of input/output pins that your programs can use to talk to and control hardware, making them well-suited for use in robotics, home automation, art installations, etc.

Being Linux computers, you can write and run programs on them using any language you like, but the Raspberry Pi community mostly revolves around Python. Raspberry Pis come with Python 2 and 3 installed, including the Python Rpi.GPIO library that makes it easy for your programs to control the Raspberry Pi's GPIO (General Purpose Input/Output) pins. They also come with the IDLE Python IDE, but you can use other IDEs (or text editors) too, such as PyCharm free Community Edition, which I use.

Hello World, plus HATs

Remember the last meetup, where we were doing "Hello World!" with different languages and web frameworks? Well, when you're getting started with a Raspberry Pi (or Arduino, or Android Things), the "Hello World" equivalent is to connect and blink an LED. A breadboard is a tool that lets you easily make circuits and connections by poking wires and components into it -- everything is reusable, and you don't need to do any soldering. Adafruit has a product called the Cobbler which I have here, and which connects to the Raspberry Pi with a cable, and then plugs into a breadboard, to make all Raspberry Pi pins labeled and easily accessible from the breadboard, but you can also just use jumper wires to connect individual Raspberry Pi pins one at a time to a breadboard.

(I retrieve my Raspberry Pi from the audience, plug the Cobbler into it, plug in a keyboard, mouse, and cable to a giant display on the wall, and power it up.)

For the hardware part of this example we're going to use a jumper wire to connect one of the Raspberry Pi's Ground pins to one end of this 330-ohm resistor, then we're connecting the other end of the 330-ohm resistor to the negative pin of this LED, and then using another jumper wire to connect the Raspberry Pi's GPIO20 pin to the positive pin of the LED. (I didn't choose GPIO pin 20 for any particular reason - you can use whichever GPIO pin or pins you like so long as you use the same pins in your software.)

For the software part of this example we have hello_world_blink.py.

(I do a walk-through of the code and run it.)

In addition to building your own circuits or prototypes, you can also buy pre-built add-on boards called "HAT"s ("Hardware Attached on Top") that plug onto the Raspberry Pi's pins and extend your Raspberry Pi's functionality with components like sensors, buttons, displays, etc., and may come with their own Python libraries to make them really easy to use in your programs.

Raspberry Pi Instagram Slide and Video Show

I'm a volunteer at the Idea Fab Labs maker/hacker/artspace here in Santa Cruz, and I was asked to set up a Raspberry Pi for our weekly open house and for IFL booths at events, so that all you had to do was plug it into a large monitor and it would start running a slideshow of Idea Fab Labs' Instagram feed of photos of projects, facilities, and events.

I had written my original Raspberry Pi Instagram Slideshow version in Python using the Tkinter GUI, but when I was asked to update it to include Instagram videos as well as photos, I rewrote it (still in Python) using the cross-platform (you can run your same Python application on Windows, OS X, Android, and iOS, in addition to Raspberry Pi/Linux) Kivy Framework.

(I demonstrate my Raspberry Pi Instagram Slide and Video Show application.)

Free Giant Amazing Raspberry Pi Project Books!

There are three official Raspberry Pi project books that are free online, each one 200 lavishly-illustrated pages of projects and articles (including beginner's guides). You'll see projects for gaming, music, robotics, Lego, telescope control, high-altitude photography, terrarium lighting control, etc. etc. etc.

(I load The Official Raspberry Pi Projects Book into a browser window on the Raspberry Pi.)

Have fun!

So get a Raspberry Pi, and have fun! A lot of people are hesitant to try hardware projects with their computers because they have no idea where to start, and are afraid they might fry their computers. But the Raspberry Pi is not only built for hardware projects and very beginner-friendly and Python-friendly, but also very cheap, in case of those rare occasions where worst really does come to worst.

A Cautionary Tale

"Have fun!" would normally be the end of the story, but in this case I also have a postscript:

If you remember the "HAT"s, well, when I was writing my script for this presentation, and concluded it with the part about not worrying about frying your computer, I thought, oh, I have an "Android Things" "Rainbow HAT" board which is supposedly also compatible with the Raspberry Pi, I should demo that in my presentation as well. And I plugged it into my Raspberry Pi, and powered up, and it didn't boot. And I powered down, unplugged the Rainbow HAT, powered up again, and still nothing.

A Raspberry Pi stores the OS and all your files on a micro SD card, which helps keep it very cheap, but in my experience they can be kind of sensitive, and in this case it had gotten fried not just to the point where I would need to use my laptop to reformat it and recopy a system image to it, but to the point where it would just not even format. And because I didn't have a spare one (which is like a $5 part) and hadn't backed up my existing one before this happened, it was a mad dash to get a new one and download/install/compile lots of packages that I use in time to be able to do this presentation this evening.

So yes, have fun! But it's also good to play it safe by having one or more spare SD cards, and backing up a system image of your SD card to your laptop or desktop after you've installed everything in sight on it.

tachyonlabs/raspberry_pi_pyladies_presentation