My take on the Singulation is definitely less conservative space wise, but improves multiple Things such as power consumption (I measured a 7 Hour Battery life with a single 3.7v 1200mah 18650) 

Unlike its predecessor which used a Teensy 3.2, this one uses an ESP32 Allowing it the access of Wifi and Bluetooth, which definitely opens up a lot of possibilities for cartridge configurations

However it takes from its predecessor in some ways too, keeping the same 5 button config as well as a hot swappable 18650 which frees the inside from the need of a charging circuit and if it dies you can just pop a new fresh battery in it, also despite not being a VFD its still a 20x4 Display which also slightly improves battery life and avoids struggling with dangerous high voltage as we don't need to fluoresce the screen

Via the voltage divider, It can sense it own battery's voltage allowing it to show accurate batter readings in 3 stages stage 1: Full and ready to go! Stage 2: about half way still ready to go! Stage 3: Low, display might start flickering, and it will become less responsive But still functional

Each cartridge slot has access to the I2C bus via an I2C Multiplexer and contains one pin that detects when a cartridge is inserted (This is done by checking if the pin is pulled down) And when it is and the cartridge number has been selected, it will run an I2C scan to check the address and match it to the programmed section for that specific cart

Cartridge possibilities are endless, from Bluetooth Speaker cartridges, to Temperature sensors, even as far as heart rate monitors, the possibilities and uses are endless

(Demo Video)

(Note: This Project is still a work in progress software wise once it has been polished and finalized a full tutorial will be made for it but for now the STLs and current code files will be uploaded Use them as you see fit!!)