Introducing NEMO for the M5Stick C Plus

I've been working on this project for a couple of weeks, and it's pretty close to finished. I've been trying to build some more skills in the embedded systems, microcontroller and Internet of Things realm, and when I decided it was time to expand my experience to ESP32, I wanted a dev kit with a little bit of everything built in. I already have breadboards, displays, servos, sensors, LEDs and accessories galore. I just wanted something cute that'd keep my interest for a while. Enter the M5Stack M5Stick C Plus. Powered by an ESP32, featuring an AXP192 power management unit, accelerometer, IR and red LEDs, a 100mAh battery, microphone, speaker, display, a few buttons and plenty of exposed GPIO pins, it seemed like a good place to start.

My usual method of learning involves sketching out a rough plan for demonstrating mastery of core concepts, so my first few projects were about getting the ESP-IDF and arduino environments working with simple programs. I also ported CircuitPython to it for some of my early projects. I focused on the WiFi stack and designing user interfaces at first, then using UART, SPI and I2C via the GPIO pins.

With most of the tech community excited about the Flipper Zero, I started thinking about what sorts of high-tech pranks one could get away with on a platform like this. The end result is NEMO, named after the titular character in Finding Nemo, in contrast to some other high-tech toy named after a fictional dolphin.

The Stick C Plus has no IR sensor, but it does have a transmitter. Infrared replay attacks might work if you plugged an IR receiver into the GPIO, but I'm not worried about that. I settled for an implementation of TV-B-Gone, relying on previous work by Ken Shirriff and a local hacker, MrARM. I had previously messed with similar projects in both CircuitPython, and at the source-code level, way back in 2008 with the DefCon 16 badge, which also featured an infrared TV killer mode.

Right about the time I was starting to work on this, DefCon 31 was wrapping up, and a ton of folks were commenting on the bizarre behavior of their iOS devices at the conference, seemingly always displaying pop-ups trying to connect AirPods or other accessories. This became known as the "AppleJuice" attack, and relies on bluetooth low energy beacon advertisements, and iOS's user experience that tries to make device pairing easier. I found a very bare-bones implementation for ESP32, that was somewhat broken.  I fixed it and gave it a decent two-button user interface as well.

I rounded out the pranks with WiFi Spamming, using a list of funny WiFi SSIDs, the now-popular "RickRoll" SSIDs and a mode that spams hundreds of randomly-named SSIDs per minute.

It defaults to a "watch" mode with a 24-hour clock backed by the on-board real-time-clock. There's a few kilobytes of non-volatile EEPROM storage on board, of which I'm using a few bytes to keep settings like left/right hand rotation, brightness, auto-dimming timer and TV-B-Gone region settings persistent through deep sleep or power off mode. All in all, it's a few existing projects just kind of glued together in a novel way that's easy to use. Those who've known me for a while would say that's on-brand. 

A few people have asked me if it's for sale. I have no plans to sell anything, such as M5Stick units pre-flashed with NEMO. This is open-source software I put together for fun, and anyone can use it and extend it. You can buy the device and learn how to load my code on it, but I'd be more excites to hear about people being inspired to build their own cool projects on it. 

At $20-$30 depending on the site and accessories you get with the M5Stick C Plus, it has a lot of capabilities. Here's an Amazon Affiliate Link to buy a version with a watch strap, lego mounting and wall-mounting options. The project source code and pre-compiled binaries are up on the m5stick-NEMO GitHub repository, and I am keeping the project up to date in the M5Burner app. You can see a quick walk-through reel on my Instagram as well.


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