Google AIY Vision Bonnet & Accessories

The key component of a Google AIY Vision kit is the “Vision Bonnet”, a small circuit board to sit atop the Raspberry Pi Zero WH bundled in the kit. In addition to all the data interface available via the standard Raspberry Pi GPIO pins, this peripheral also gets “first dibs” on raw camera data. The camera itself is a standard Raspberry Pi Camera V2.1 but instead of connecting directly to the Raspbery Pi Zero, the camera cable connects directly to the vision bonnet. There is then a second cable connecting from vision bonnet to the Raspberry Pi camera connector, for the bonnet to forward camera data to the Pi after Vision Bonnet is done processing it. This architecture ensures the Vision Bonnet will never be constrained by data interface limitations onboard the Pi. It can get raw camera feed and do its magic before camera data even gets into a Pi.

The vision coprocessor on this Vision Bonnet circuit board is a Movidius Myriad MA2450, launched in 2016 and discontinued in 2020. Based on its application here, I infer the chip can accelerate inference operations for vision-based convolutional neural networks that fit within constraints outlined in the AIY Vision documentation. I don’t know enough about the field of machine vision to judge whether these constraints are typical or if they pose an unreasonable burden. What I do know is that, now that everything has been discontinued, I probably shouldn’t spend much more time studying this hardware.

My interest in commercially available vision coprocessors has since shifted to Luxonis OAK-D and related products. In addition to a camera array (two monochrome cameras for stereoscopic vision and one color camera for object detailed) it is built around Luxonis OAK SoM (System on Module) built around the newer Movidius Myriad MA2485 chip. Luxonis has also provided far more software support and product documentation on their OAK modules than Google ever did for their AIY Vision Bonnet.

I didn’t notice much of interest on the back side of AIY Vision Bonnet. The most prominent chip is marked U2, an Atmel (now Microchip) SAM-D.

The remainder of hardware consists of a large clear button with three LEDs embedded within. (Red, green, and blue.) That button hosts a small circuit board that connects to the vision bonnet via a small ribbon cable. It also hosts connectors for the piezo buzzer and the camera activity (“privacy”) LED. The button module appears identical to the counterpart in AIY Voice kit (right side of picture for comparison) but since voice kit lacked piezo buzzer or LED, it lacked the additional circuit board.

Google AIY Vision Kit

A few years ago, I tried out the Google AIY “Voice” and “Vision” kits. They featured very novel hardware but that alone was not enough. Speaking as someone not already well-versed in AI software of the time, there was not enough documentation support to get people like me onboard to do interesting things with that novel hardware. People like me could load the default demo programs, we could make minor modifications to it, but using that hardware for something new required climbing a steep learning curve.

At one point I mounted the box to my Sawppy rover’s instrument mast, indicating my aspirations to use it for rover vision, but I never got much of anywhere.

The software stack also left something to be desired, as it built on top of Raspberry Pi OS but was fragile and easily broken by Raspberry Pi updates. Reviewing my notes, I realized I published my notes on AIY Voice but the information on AIY Vision was still sitting in my “Drafts” section. Oops! Here it is for posterity before I move on.

Google AIY Vision Kit

The product packaging is wonderful. This was from the era of Google building retail products from easily recycled cardboard. All parts were laid out and neatly labeled in a cardboard box.

Google AIY online instructions.jpg

There was no instruction booklet in the box, just a pointer to assembly instructions online. While fairly easy to follow, note that instructions were written for people who already know how to handle bare electronic circuit boards. Handle the circuit boards by the edges and avoid touching components (especially electrical contacts) and such. Complete beginners unaware of basics might ruin their AIY kit.

Google AIY Vision Kit major components

From a hardware architecture perspective, the key is the AIY Vision bonnet that sat on top of a Raspberry Pi Zero WH. (W = WiFi, H = with presoldered header pins.) In addition to connection with all Pi Zero GPIO pins, it also connects to the Pi camera connector for direct access to camera feed. (Normal data path: Camera –> Pi Zero. AIY Vision data path: Camera –> Vision Bonnet –> Pi.) In addition to the camera, there is a piezo buzzer for auditory feedback, a standalone green LED to indicate camera is live (“Privacy LED”), and a big arcade-style button with embedded LEDs.

Once assembled, we could install and run several visual processing models posted online. If we want to go beyond that, there are instructions on how to compile trained TensorFlow models for hardware accelerated inference by the AIY Vision Bonnet. And if those words don’t mean anything (it didn’t to me when I played with the AIY Vision) then we’re up a creek. That was bad back then, and now that a few years have gone by, things have gotten worse.

  1. The official Google AIY system images for Raspberry Pi hasn’t been updated since April 2021. And we can’t just take it and pick up more recent updates, because that breaks bonnet functionality.
  2. The vision bonnet model compiler is only tested to work on Ubuntu 14.04, whose maintenance updates ended in 2019.
  3. Example Python code is in Python 2, whose support ended January 1st, 2020.
  4. Example TensorFlow information are for the now-obsolete TensorFlow 1. TensorFlow 2 was a huge breaking change, and it takes a lot of work — not to mention expertise — to migrate from TF1.x to TF2.

All of these factors together tell me the Google AIY Vision bonnet has been left to the dusty paths of history. My unit has only ever ran the default “Joy Detection” demo, and I expect this AIY Vision Bonnet will never run anything else. Thankfully, the rest of the hardware (Raspberry Pi Zero WH, camera, etc.) should have better prospects of finding another use in the future.

Google AIY System Image Still Fragile

After exploring a Google AIY Voice kit’s capabilities and found it promising for future projects, I thought it was a pretty good deal at the clearance price of $15. Sadly for Google and Target, I still think its original price of $50 is high for what we get in the box. And that’s before I ran into what appears to be a recurring problem with the Google AIY kits: their customized build of Raspbian is very fragile and has a history of failing after system updates.

Google AIY Voice Bonnet

Of course, I didn’t realize the root cause immediately. When I initially booted up my box, with USB keyboard+mouse and HDMI cable attached, I ran through its initial setup procedure which helped me log on to my local network, change the default password to something other than ‘raspberry’, tasks of those nature. One of these steps was whether I wanted to download and install updates. Even though I followed instructions to download the latest system image, as of right now the “latest” is still from this past November and missing quite a few security patches since. I had continued playing with the hardware while updates installed, fiddling with things as I went. Eventually I had to reboot the box and when it came back up, everything has fallen apart.

I was in the middle of playing with aplay and arecord so my first symptom was a complaint of missing sound hardware. Since by then I had already established that they are standard Linux sound devices under ALSA (Advanced Linux Sound Architecture) I started looking up resources online to debug ALSA sound hardware running on a Raspberry Pi. This, I have since found out, is a huge bag of hurt best summarized by the following passage from this StackExchange thread:

However, at no time in history has mankind produced such an amount of useless and dysfunctional diagrams, as for trying to explain ALSA.

That’s just one man’s opinion, of course, but after several hours of banging my head against ALSA brick walls I saw nothing to contradict that opinion. Even Adafruit, typically the benchmark of clear concise tutorials, could only offer this mess which falls far short of their typical standards.

I was almost ready to give up on the whole works when I remembered to run a LED test and found that also failed with an error message Leds are not available on this board. That’s when I finally realized it’s not just the sound hardware, everything on board Voice Bonnet has gone offline. I’m not enough of a Linux expert to understand the details of what went wrong, but apparently certain types of system upgrades would wipe out all the customization required to support Voice Bonnet hardware.

This comment on a Github issues discussion thread suggested running a whole bunch of sudo dpkg-reconfigure commands to bring them all back. This might be worth trying some point later. But for today’s experimentation I re-imaged my microSD card and set up the box again – this time declining to download and install all updates. It’s a very insecure workaround, but today I only need to continue experimenting with the hardware. I’ll have to see if this problem is updated when I want to use this hardware for an actual project.

Bottom line: it’s very disappointing to have Google’s custom AIY version of Raspbian stop working on Google AIY hardware after certain system updates. I’m sure some number of these incidents resulted in the product getting returned to Target under their generous refund policy, which wouldn’t be very helpful to retail success at all.

Examining Google AIY Voice Bonnet LED and Pins

The default demo for a Google AIY Voice kit turns a Raspberry Pi Zero in a cardboard box into a Google Voice Assistant. I wasn’t terribly interested in that at full price, but at clearance discount they were interesting enough to purchase. I had fun looking over its “Voice Bonnet” audio accessory board to verify it is easy to re-purpose to sound-based projects of my own choosing. Once that primary goal was complete, I looked at some of the auxiliary features on that accessory board to see what’s going on.

Google AIY Voice Bonnet

First up is aiy.board which interfaces with the big plastic button. It looks like the kind of button found on an arcade console and I would expect it to be durable for many cycles. The source file has all the code dealing with the messy realities of dealing with a physical button, including logic to handle debouncing.

Next is aiy.leds. When assembling that button, I noticed it had more pins than strictly necessary for a button and it turns out the button also incorporates a RGB LED array. While aiy.board has code to deal with that LED array, comments indicate there’s a better API available elsewhere for the RGB LED in the aiy.leds source file. Indeed there appears to be better support for lighting effects like blinking, pulsing, and color blending.

Finally aiy.pins allows access to the GPIO pins exposed by Voice Bonnet. I had originally thought these were passed through from the Raspberry Pi GPIO bins, but further reading indicates I was wrong. These pins are controlled by the SAM D microcontroller on board the bonnet, and aiy.pins expose them for use in a way compatible with Raspberry Pi’s gpiozero library.

This looks like a pretty decent set of auxiliary functionality available on the Voice Bonnet, certainly enough to handle some simple projects without pulling in additional hardware. Also, the RGB button and auxiliary pins are apparently shared between the Voice and Vision bonnets so common code can drive both. This may prove useful somewhere down the line.

Google AIY Voice Bonnet Will Be Easy To Repurpose

Google’s AIY products were an experiment to bring a hands-on building experience to retail storefronts. It’s the kind of thing one would expect to find at Radio Shack, if Radio Shack were still alive. Sadly, with the AIY Voice kit marked down for clearance at my local Target, the experiment did not appear to be a resounding success. Still it means I now have a Google AIY voice kit to play with.

Just for the sake of seeing how it was supposed to come together, I followed assembly instructions even though I had no interest in building my own Google voice assistant for my home. Or at least, I got it set up far enough to have the mechanical box on my home network. I stopped before completing the steps to sign up for Google Assistant API access and enrolling this piece of hardware.

What it means is that I now have a Raspberry Pi Zero on my home network, coupled with “Voice Bonnet” audio hardware that I can now learn more about.

Google AIY Voice Bonnet

It appears all the code to interface with this Voice Bonnet is documented and available online. I went straight to the APIs to see how one interacts with the audio capabilities. I had expected to find code interfacing with device drivers and hardware registers, I didn’t expect that the source file mostly consists of code that calls out to standard command-line audio utilities arecord and aplay.

I then looked into the default text-to-speech capabilities inside aiy.voice.tts and found much of the same: text is sent out to a command-line utility pico2wave which does all the hard work. It generates a sound file, which is then sent to aplay for playback.

This is great news: this meant it will be trivial to use the audio recording and playback capabilities of this Voice Bonnet for purposes other than interacting with Google voice assistant platform.

Hello Google AIY Voice Kit

As someone who have played with electronics modules purchased online for a wide variety of projects, I was fascinated by Google’s AIY projects a.k.a do it yourself artificial intelligence line of products. Here in the United States, Google is not doing it alone. The products themselves are not enough if it isn’t in front of people’s faces, so there was also a partnership with the retail giant Target to have these kits on the shelves of Target stores. I didn’t think there is large enough of a market for these products willing to pay the prices it would take to justify a retail presence, but I admire the willingness to put up the money for an experiment to find out.

There were two kits: the AIY Voice kit and the AIY Vision kit. The vision kit costs roughly double that of the voice kit ($90 vs. $50) but it was far more interesting with an onboard Pi camera and a TensorFlow processor designed to accelerate machine vision tasks. When the vision kit became available at my local Target, I immediately purchased one so I could play around with its default demo software. Sadly my TensorFlow knowledge is still too weak for me to make the vision kit do my own bidding.

As for the voice kit, I knew it was also built around a Raspberry Pi Zero with a hardware accessory board, but that board was focused on audio capture and playback not significantly different from a sound card. I was not aware of any audio processing capability on board, so I expected the audio to be recorded and uploaded to Google for processing. This capability was not interesting enough for me to buy one at $50.

It’s been over a year since the retail experiment began, and my local Target has marked the AIY Voice kit for clearance sale at $15 each. (I later found out Micro Center was even more aggressively clearing them out at $5 each.) I guess this means we have an answer to that experiment. I’m a little sad to learn of this, because I would have loved to be proven wrong. If there was indeed a market for a successful product in this area that would have meant more interesting products for me to purchase locally. Alas, it looks like I’ll continue to buy esoteric little electronics gadgets online.

Still, right now I could pick up an AIY Voice kit for $15. The Raspberry Pi Zero at the heart of the device has a retail value of roughly $10 all by itself. Add in the microSD card and we’re pretty close to $15 before considering the rest of the kit. I passed on the AIY Voice kit at $50, but I’m willing to buy them at $15. Worst case scenario, I will have a Raspberry Pi Zero W and matching microSD card.

Here’s what I saw when I opened the box:

Google AIY Voice Kit

There were no surprises. Aside from the expected Raspberry Pi Zero W and microSD card, we have the hardware accessory called a “Voice Bonnet”.

Google AIY Voice Bonnet

The remaining hardware components are a single speaker and a big button (that turned out to have LEDs in it) and they plug into this bonnet.

Let’s see what this kit has to offer.