[chbot] 4G Modem / Phone Info

[Michael, eDIY Software]

Hi all,

This is the video that recently got me thinking more about mobile phone privacy issues. Rob Braxman keeps surprising me with big picture arguments regarding data collection. If this is a topic that interests you, check out some of his other videos.

Client Side Scanning - See What You See

https://www.youtube.com/watch?v=6bPJzLXdEcA

I was amazed Google had actually installed this software on my phone without saying anything, and not getting a choice if I wanted them to machine-learn my local data.  I would be interested to know if you find this software on your phone (if using Android, check your installed applications) and if you knew anything about it or what you think about it?

Likewise with MS Windows 11 turning on the (newly installed via an update) Recall feature without saying anything and/or giving an opt-out notice.  I had to be told it existed, and then had to manually turn it off in the settings.  

DIY Mobile Phone

The modem model is UZ801 v3.2 using a Broadcomm MSM8916 SoC - currently only NZD$10.66: https://www.aliexpress.com/item/1005008609322445.html

The screen and ESP32 combo (known as a CYD) is what I brought in a while back (price rise from the NZ$11.98 I paid back then):  https://www.aliexpress.com/item/1005006160645147.html

A MicroPython (https://micropython.org/) + LVGL (https://docs.lvgl.io/master/details/integration/bindings/micropython.html) binary is running on the CYD ESP32 board for the user interface, which connects to the 4G stick via WiFi and uses MQTT for signalling.

The OS on the 4G Modem is Debian Linux (https://github.com/msm8916-mainline/linux) and the Qualcomm modem drivers (these drivers are binaries copied from the stock Android system that runs on the 4G modem by default.  You can actually take a screenshot of the Android login screen and press buttons on it using adb, even though there's no physical screen.),

BareSIP (https://github.com/baresip/baresip - an amazingly well put together SIP client) for voice calls over the data connection. I couldn't get SIP text messages to work, I think it's might be 2talk not passing them on but apparently they support them, so not sure what's going on there.  

Mosquitto (https://mosquitto.org/) as the MQTT broker to act as a central control signal router. BareSIP allows any of its commands to be run from MQTT and there's a way to run shell commands for mmcli from MQTT as well)

The ModemManager command line to send and receive SMS messages. Here, I couldn't get 4G voice calls to work, it all seems fine from the logging of the LTE call initiation data, but the target phone never rings and the call doesn't get registered in the Skinny account call history.  

In Summary

This will work well enough to get the job done, the voice calls would come from one phone number (SIP), and the SMS messages from another one (SIM), but that's no big deal.   

A benefit of running the 4G Modem as a Wifi access point (mainly for the ESP32 display data connection) is that it can be used by other devices as well, eg a laptop. It can also act as bluetooth media source, so I can run mplayer and listen to music from the local storage.  

I reckon I can get it to be a reasonably good dumb phone that I can use for normal phone requirements. Because it's so modular it could be split into pieces. The display could be on a wrist strap holder, the 4G modem and the hub and bits could be on a belt clip, and the headset is a bluetooth headband that I can wear in my helmet.  

For anything else I can use a PC, Laptop or tablet that can share the 4G internet connection or use local WiFi.

Privacy wise, the modem drivers are closed source, but the application side is open source enough to know what data "should" be being transmitted, and there's complete control over the installed applications.  

 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ourshack.com/pipermail/chchrobotics/attachments/20250317/1ce28a80/attachment-0001.html>