I just finished writing and testing my first extension to the Klipper firmware base that allows me to use a spare thermistor and a logic-level MOSFET plus 2 resistors to thermostatically control the BigBox output fan. Why was this worth doing? The back side of the printer faces me when I sit at my desk (power cord issue). The exhaust fan is the loudest mechanical device on my BogBox now, thanks to TMC stepper drivers. Turning on the exhaust fan only when it is needed is a nice difference to always hearing the fan running! What made this functional extension possible for me is Klipper firmware. Klipper firmware (written by Kevin O'Connor with contributions by others) is composed of two parts: The computational portion of the printer firmware which runs on a Linux machine (the Raspberry Pi 3 works very well but I debugged some code running this portion of the firmware on an old laptop running Linux). This code also integrates nicely with OctoPrint running on the same Linux host and work is underway to make it work with Repetier. The I/O portion of the firmware runs on MCUs like the ATmega2560 on the Rumba card. Work is underway to port it to the Arduino Due, Beagleboard and Smoothieboard The computational portion of the firmware is written in python and designed with a modular approach that allows the developers and users to create event driven functional extensions (like my thermostatically controlled exhaust fan). It is also written to work with multiple MCUs simultaneously if desired. The communication link between the Linux host processor and the MCU(s) is over USB. The I/O portion is written in C and compiled for the target MCU(s). It is a work in progress and will be for quite a while, however, I have been using it exclusively lately and have not turned back to Marlin. Some highlights: The price point is excellent (add the cost of a RPi3 plus power supply and USB cable). You don't rewire the I/O devices. The Raspberry Pi 3 and up include wifi. A nice video camera can be added for about $45 so you can watch your printer at work (or not working as it should). The stepping rates go from about 10k steps/second with the Marlin base on an 8 bit ATmega platform like Rumba (which is doing all of the work) to somewhere around 175k steps/second with 25 usec resolution! Using the Zesty Nimble extruder with a 30:1 gear reduction means 10x the number of steps are needed compared with Titan to move filament the same distance. This is not a problem with a six stepper platform running on an 8 bit mcu plus Raspberry Pi 3 and Klipper firmware. New features are being added by the user community regularly You can create your own new features - you have an event driven, written in python code base. (An example: the simple thermostatically controlled fan code was extended by another user to do full pid feedback) If you are still reading this, my hope is to let the BigBox community know of another way to add new life to our printer!