Compact electrotactile stimulation and EMG acquisition system with embedded blanking of stimulation artifacts

We present a miniaturized closed-loop system for myoelectric control and electrotactile feedback in upper limb prostheses. The system integrates an electrotactile stimulator, which allows synchronous and asynchronous distribution of stimulation pulses, and an acquisition system for the simultaneous recording of multichannel EMG. The stimulator generates biphasic, current controlled pulses (amplitude: 0-5 mA; duration: 50-500 us; frequency: 1-100 Hz), which are routed by a demultiplexing circuitry to any of the 16 output channels. The acquisition system can be configured to record 8 bipolar or 16 monopolar EMG channels with a sampling frequency in the range from 500 Hz to 2 kHz. Embedded firmware incorporates direct calculation of ARV or RMS in the defined time window, as well as direct blanking of recording channels for the duration of the stimulation pulse artifact. Based on initial tests in a simple experimental setup we can determine that the developed system and proposed blanking algorithm can be used to record EMG signals during simultaneous delivery of electrical stimulation in challenging conditions (e.g., close electrode placement, high stimulation intensity).