The Tethered Haptics Using Morse Pulses (THUMP) subsystem is now working on the TRILLSAT-1 prototype which allows two-way haptic communication using the A-Z subset of International Morse Code.  It operates in parallel on both ATtiny CPUs, and creates its own serial bus protocol for daisy-chained, asynchronous operation.  I've published a separate project page for it called #Tethered Haptics Using Morse Pulses and entered that project into the 2018 Human Computer Interface Challenge.  I also released my SIMTHEO Decoder module source code under LGPL 3.0.  It can be useful for a variety of different types of tethered robots, such as hoistbots and winchbots (and oblique, capstan cablebots, like TrillSat).  I will release the updates to the TrillSat source code when I get a chance, which will show exactly how the THUMP subsystem is applied to the TRILLSAT-1 prototype.