Raspberry Pi 3 Model A+ - Review

Table of contents

RoadTest: Raspberry Pi 3 Model A+

Author: rancell

Creation date: 29 Jun 2019

Evaluation Type: Development Boards & Tools

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: Raspberry Pi 3 Model B+, Raspberry Pi Zero

What were the biggest problems encountered?: The hardest part was probably connecting and disconnecting cables to the Pi, as it's so small!

Detailed Review:

For this road test I received a Raspberry Pi 3 Model A+. I'm going to use it to replace an garage door opener I made using a Raspberry Pi Zero. The garage door opener runs a web server that allows you to open and close the garage door when on the local WiFi network - the sort of project that first nicely into the Raspberry Pi platform. While I'm pretty happy with the Raspbian OS used in the existing server, it does have the downside of having a being yet another device to manage. I want to try using Ubuntu Core on the replacement to make this easier.

In the picture below my helpful assistants show you what comes in the small cardboard box.

There are three models in the modern Raspberry Pi family (ignoring the Pi 4 which came out as I wrote this):

• Model B+ is the main board and the benchmark I'll compare the other two against.
• The A+ is effectively the same as the B+, but with the USB and Ethernet ports removed (one USB left behind) and half the RAM (512Mb).
• The Zero is a super cheap cut down version of Raspberry Pi. The performance is nearer that of the Raspberry Pi 2 and it has very limited connectivity.

There are two things you need you need to buy to make use of a Raspberry Pi:

1. A micro SD card.
2. A micro USB power supply.

In addition, I highly recommend you get a USB hub / Ethernet adapter. When plugged into the A+ or Zero this makes the connectivity essentially the same as the B+. So you can easily connect a keyboard and mouse during development, then remove these later when your project is ready. If you permanently need such connectivity I'd just consider getting a B+ in the first place.

Finally you probably want to get a case to protect the Pi when you're finished. There are many suppliers that make these so you should be able to find something suitable.

The Existing Project

The requirements for the existing project were quite simple:

• It had to be simple and easy to maintain, ideally not depending on some web service to work.
• It had to to pulse a relay to control the garage door motor.
• It had to be cheap.

A Pi Zero running Raspbian and a Python web server solved this nicely. The Pi connects to the local WiFi network and serves a page that contains a button to open or close the door. This works the same as pressing the button on the wall in the garage.

The relay connects to the garage door motor but I wont show how I have it connected. If you are interested in building a similar system then you need to check how your particular garage door works and ensure you have it wired up safely.

The New Project

I had originally wanted to run Ubuntu Core on the Raspberry Pi for the following reasons:

• I just want the minimal amount of software running. Less things to go wrong and less security risks.
• I'd like my application to be in a sandbox - that way any mistakes I have made in it are limited in what damage they do. Apps on Ubuntu Core are packaged using the Snap format which supports sandboxing.
• I want to be able to update my application remotely and have the box pick this up automatically. I can do this by putting my app in the Snap Store.

However Ubuntu doesn't support the Zero as the CPU is too old, so I either had to use a full Model B+ which was more expensive or stick with Raspbian on the Zero. Just after I completed the project the A+ was released, and I now can have both a cheap device and Ubuntu Core. Yay!

Installing Ubuntu Core

First step is the downloads page at raspberrypi.org, which lists Ubuntu Core as one of the suggested third party operating systems. The instructions are fairly easy, and involve downloading an image (238Mb), writing it to a SD card and then booting the Pi.

After boot I entered the following when prompted:

• WiFi details.
• My email address (connected to my Ubuntu account).

And that's it. The final screen shows the exact command I need to run to log into this box, and no password needs to be entered as it's already used the SSH key attached to my account. I can now unplug the mouse, keyboard and monitor and develop everything from my laptop.

Creating a Snap

To make this project into a snap I did the following:

1. Uploaded the project to GitHub.
2. Created some Snap metadata to describe this snap. This is made up of:
   • Text descriptions.
   • Build instructions.
   • The permissions this snap needs to run in the sandbox (access to the gpio pins and the ability to bind to port 80 for the web server).
   • How to run the server.
3. Connected up the build servers to automatically build the snap on suitable ARM hardware.

After some iterations to get things right, the snaps are automatically built and appear in the snap store page.

Setting up the Device

I connected up a relay to the 3V, GND and GPIO4 pins on the Raspberry Pi and installed the app with the following commands from my laptop:

ssh robert-ancell@192.168.1.192

snap install garage-door

snap connect garage-door:gpio pi:bcm-gpio-4

snap start garage-door

Here is the finished product. When I browse to 192.168.1.192 I can control the relay and open/close the garage door. Ready to replace the existing Pi Zero!

The great thing about using Ubuntu Core is this device will automatically update both the OS software and my app every time I upload a new version. And if I want another device I can just buy another Raspberry Pi, install Ubuntu Core and run the same commands.

Conclusions

The A+ is a welcome addition to the Raspberry Pi family. It fits the case where you want to make an affordable embedded device that doesn't need all the connectivity of the standard B+ Raspberry Pi model but you want to be able to use Ubuntu (which the Zero can't). Ubuntu Core was easy to install and ran fast on this device.

While not as tiny as the Zero the A+ is a very compact size and easy to hide away. There's plenty of good case options available to protect it.

The only negative on this board is the lack of connectivity, but a simple USB hub / Ethernet adapter resolves this for development purposes. For this project I was happy to use WiFi for network access but if I needed Ethernet then additional hardware would have been required. Though this is not particularly expensive it would eat away some of the savings over the Model B+.

I'd use the Raspberry Pi + Ubuntu Core combination again and I hope this review has been helpful for anyone else interested in trying that!