Figure 1: ONIX, a unified open-source platform for unencumbered freely moving recordings.

a, Simplified block diagram of the ONI (open neuro interface), illustrated via the tetrode headstage: multiple devices all communicate with the host PC over a single micro-coax cable via a serialization protocol, making it possible to design small multi-function headstages. b, The integrated inertial measurement unit and 3D-tracking redundantly measure animal rotation, which drives the motorized commutator without the need to measure tether torque. Small drive implants⁴⁴ enable low-profile implants (~20 mm total height). c, The ONIX micro-coax, a 0.31 mm thin tether of up to 12 m length, compared to standard 12-wire digital tethers. d, Torque exerted on an animal’s head by tethers. Current tethers allow full mobility only in small arenas and in situations when the tether does not pull on the implant, while the ONIX micro-coax applies negligible torque. e, Performance of ONIX: With the 64 channel headstage, a 99.9% worst case closed-loop latency, from neural voltage reading, to host PC, and back to the headstage (e.g. to trigger an LED) of <1 ms can be achieved on Windows 10 (see also Suppl. Figs 6 & 7).