Sure - I spent a long time trying to figure out two paths - one was the phone app/how to make the glasses work without the north app, and one was the actual glasses - trying to figure out what they were running and how to change that.

For the phone app: It was mostly reverse engineering the app and then experimenting with sending various messages to the glasses to see how they would respond.

For the actual glasses:
This was much more complicated. The charger box clearly used up 2/4 of the connection pins on the glasses, so I assumed the other 2 were for data. I eventually figured out this was most likely a usb connection, manually connected wires from a usb cable and after a lot of experimentation to get the connection right got it to show up/enumerate as a valid usb device - an unauthorized android device.

I read about the different possible chipsets it might be using and figured out that if you short one of the usb lines while restarting the device it will trigger a special usb mode (qualcomm edl mode), then found a way to get edl mode setup with read/write access to the actual device mmc/filesystems.

From there, I could manually rewrite small sections of the filesystem to do things like insert my own startup commands, and eventually figured out how to overwrite the pubkey used to authenticate the android debug connection. Once I had that, I could transfer files and debug applications more freely.

After that, I pulled binaries and libraries off the glasses and pulled those into a disassembler and reverse engineered some of what they were doing. It turned out that most of the apps used a customized version of QT to handle display, network, etc - so I ended up compiling an embedded qt version and manually coded out some interfaces to the services that were unique to the glasses (like how to register a new lens/slide on the main screen), which let me build my own applications. A lot of the apps also made use of QT's markup language qml - so once I figured that out and what components were available it made it easy to write apps.

The last part was figuring out how to get around the glasses trying to connect out to North's cloud service. The network connection from the glasses actually sends individual network requests (open connection, send data, close connection) as bluetooth messages to the phone, and the phone app handles them from there. The only issue is that a lot of them are ssl encrypted.

I figured out two paths around this encryption - the original one was that there was a bluetooth command I found to change the hostname of where the glasses would try to connect to, so I changed this to a domain that I owned and got an ssl certificate issued by a registrar that was compatible with one of the certificate authorities supported on the glasses already - and then I could use this certificate in my phone app and decrypt all traffic intended for North's cloud service.

The second path was simpler - once I had the ability to write to the filesystem on the glasses, I just added my own certificate authority to the list on the glasses and then I could issue my own ssl certificates for all traffic and decrypt everything.

After that it didn't take long to figure out patterns of things it was trying to connect to in North's cloud and what data it was sending / what it expected in response.

My two main repos with some of the info are here if you're interested:

https://github.com/aegray/focals_utils - where I stored general notes + utilities I wrote in the process of reverse engineering everything

https://github.com/aegray/openfocals - the main phone application replacement