Tunable EMG Analog Frontend

EMG signals vary widely across muscle groups, electrode contact quality, and individual physiology. A fixed-gain analog frontend either clips on strong contractions or loses resolution on weak ones. Most off-the-shelf systems handle this by targeting a single application. FlexEMG makes the analog chain itself reconfigurable instead. The 8-channel frontend uses digital potentiometers and rheostats to retune amplifier gain and filter cutoffs in real time through a closed-loop. We multiplex eight low-noise instrumentation amplifiers into a single 16-bit SAR ADC to keep current draw low. A PID-based automatic gain control loop tracks the signal envelope and adjusts the pots to hold EMG bursts within the ADC’s full-scale range. Strong contractions do not clip, and weak ones still use most of the ADC’s resolution. Our first deployment used FlexEMG to drive a 4-DOF robotic arm, and that prototype won 1st place at the 2025 California Neurotech BCI Competition. FlexEMG is the analog foundation of the Doctor Octopus Initiative, our long-term effort to build working versions of the neurally controlled limbs from Spider-Man. In parallel, we have shrunk the system into a wearable: a compact board built around a nRF52840 Bluetooth module with USB-C charging, sealed in a coin-sized enclosure that snaps directly onto standard gel electrodes. We are actively working with sports scientists and physiologists to turn this into a product designed for athletes. Our first demo is linked below. Much more to come...! Partners: Sean I., Reuben T., Joseph M., Krishna M.

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