A Microcontroller based Charge Balanced Trapezoidal Stimulus Generator for FES System

Foot drop (FD) is the inability to lift the front part of the foot from the ground. It causes the toes to drag along the ground while walking and can cause fall and injuries. A patient may have FD when there is a loss of communication between the central nervous system and the peroneal nerve. It can be corrected by functional electrical stimulation (FES) of the peroneal nerve by applying pulses of a given duration, amplitude, and frequency. In this paper, we are proposing a microcontroller based FES system that produces trapezoidal, charge-balanced, biphasic stimulus output with near-zero DC level. In this design, we use a programmable ESP32 microcontroller with a built-in DAC, uniphasic to biphasic converter circuit, current amplifier and step-up transformer. Stimulation amplitude, pulse width and frequency of the stimulation pulse can easily be adjusted by using an adjustable knob. The cost of the overall system is very low and can be built using standard electronic components.