When I first wrote about the ATMegaZero, I was still a little confused about this curious hybrid between Arduino and Raspberry Pi Zero; I have more Arduinos, and more Raspberry Pis, than I can easily recall or even locate — and other than perhaps Wyolum's AlaMode, my collections have always remained distinct. In fact, I even keep my Pis and other SBCs in one giant stack of bins, and my Arduinos and other MCUs in another. I'm a huge fan of doing absurd projects just for the fun of it, but this project seemed a bit too serious for the "because I can" column — and when I saw the momentum this curious concept was generating, I had to take another look. And then I got the chance for a very close look, when creator Eddie Espinal was kind enough to send me a prototype board to evaluate!
The first surprise when I received my board — and keep in mind this was just a prototype — was the professional presentation. It arrived in a really attractive paper-clad anti-static bag similar to the BBC micro:bit, with a big ATMegaZero logo on the front — on par with or exceeding the "unboxing" (or in this case "un-not-torn-opening"?!) experience of much larger competitors. The particular kit that I received also included an ESP-01S ESP8266 Wi-Fi Module, blue OLED display, protoboard, LiPo Battery Shield, and super-snazzy colorful GPIO headers for a premium ATMegaZero experience.
The ATMegaZero is available with pre-soldered headers, but mine — as well as the included shields — shipped loose, so that I could decide for myself how to configure them. I opted for the standard male arrangement as found on the Raspberry Pi, in order to allow experimentation with my collection of HATs and pHATs — and 120 solderings later I was ready to get started with the software!
The ATMegaZero is an Arduino at heart, so setup and development is oriented around the Arduino IDE. Familiar to anyone who has ventured beyond Arduino's own first-party boards will be the Boards Manager, whose contents can be augmented by providing a JSON file in the IDE's preferences; adding and installing the ATMegaZero board in this way is all that's required — from there on out, the ATMegaZero development experience is identical to any other Arduino.
The included OLED, ESP-01S, and LiPo shields provided plenty of fodder for exploration of the ATMegaZero ecosystem, and after a quick blinky sketch upload to confirm everything was working, I walked through the OLED how-to. It's worth mentioning at this point that the connector along the right edge of the board, which on a Pi Zero would be a MIPI CSI-2 connector for the Camera Module, is actually an FPC connector for connecting an OLED display!
I happened to already have the
Adafruit_SSD1306 library installed from a recent project, so was up and running with the example very quickly — it was very cool to see the ATMegaZero logo displayed on the tiny screen — and then be able to reuse the example with my own ideas.
The ATMegaZero folks really know how to appeal to my interests, because if there's one thing I love more than adding a little screen to a project, it's slapping a LiPo and charging circuit onto it so that I can make it portable! I grabbed a 2000mAh cell and walked through the LiPo Shield demo, which again leveraged a community-developed library — this time the BQ27441-G1A LiPo Fuel Gauge Arduino Library from SparkFun. I've worked with a number of LiPo charging ICs before, but I found the TI BQ27441-G1A delightful: estimating battery capacity can be extremely difficult, and TI's fuel gauge plus SparkFun's library provide detailed, accurate metrics like charge/discharge rate, capacity, and health. One issue I ran into was somehow initially failing to notice the onboard switch which enables toggling between charging and powering from the LiPo (Espinal has since drawn attention to it in the docs/below), but once I'd located that, it was absolutely brilliant seeing the detailed charging/discharging stats. In fact, I ended up combining this with the OLED to create a self-contained LiPo battery charging and monitoring system!
The ESP8266 demo was not ready in time for my review, but I'm really looking forward to expanding the horizons of my ATMegaZero with this clever Wi-Fi integration!
More than just a round MCU peg in a square SBC hole (?!), the ATMegaZero has already evolved into its own ecosystem, with numerous available accessories and great documentation and examples. Next on my list is experimenting with my collection of HATs and pHATs to see which are 5V-tolerant and can be used to expand the platform even more! The first batch of ATMegaZero boards just arrived, and are available now in the ATMegaZero store, with an exclusive discount for our readers: enter the discount code "HACKSTER" and receive 10% off of your entire order!!