Fig. 3.

a Schematic of the synchronized neuromuscular electrical stimulation (NMES) and exoskeleton communication. The NMES device is calibrated under complete digital control from a Teensy 3.2 microcontroller and system of electromechanical relays housed on a printed circuit board (PCB). Front-end calibration occurs on a Python desktop graphical user interface. The NMES synchronizes with the exoskeleton motor control via digital input from the exoskeleton’s finite state machine. b Schematic of the gait cycle, showing how the timing of stimulation delivery during stance phase as determined by the Finite State Machine (FSM) deviates slightly from the traditional biomechanical definition