Valve has published a hardware reference repository for the Steam Frame, and it contains considerably more than a dimensions drawing.
What is in it
STEP format models of the VR core module, the head strap and the controllers. STEP is the interchange format every CAD package reads, which means designing something that fits is now a matter of importing a file rather than, as Hackaday puts it, breaking out the calipers or 3D scanning the hardware.
The locations of the IR tracking LEDs embedded in the controllers are documented. This is the detail that separates a useful release from a courteous one. Optical tracking depends on the headset seeing those LEDs; a 3D-printed grip or protective shell that covers one will degrade tracking in ways that are maddening to diagnose and easy to blame on software. Publishing the positions means a designer can check for occlusion before printing instead of after.
The front expansion port is specified. The Frame has a user-accessible hardware expansion port exposing two interfaces: high-speed MIPI camera and PCI Express — and the repository documents it with a reference design in both KiCad and Altium.
The expansion port is the significant part
MIPI CSI and PCIe are not accessory-bracket interfaces. They are the buses you attach sensors and compute with.
MIPI CSI is how camera modules talk to application processors. An exposed MIPI camera lane on a headset means a third party can add an imaging sensor that the system can actually read at full rate — a thermal camera, a high-frame-rate mono sensor, a depth module, a different field of view, a scientific sensor. Not a webcam bolted on over USB, with the latency and bandwidth ceiling that implies, but a camera in the same position in the pipeline as the ones Valve shipped.
PCI Express is wider still. PCIe on an expansion port is an invitation to attach an FPGA, an accelerator, a capture card, or custom silicon, at bandwidths and latencies that no external interface approaches.
Shipping a reference design in two EDA tools is the part that tells you this is meant to be used. A documented connector pinout is a specification; a working reference schematic in KiCad is a starting point you can fork. Including Altium alongside it covers both the hobbyist and the professional end of the tool spectrum, which is an unusual amount of consideration.
Why this matters beyond modding
For anyone building installations or research apparatus, a headset with a documented high-bandwidth expansion port is a different class of object from a sealed consumer device.
The standard problem with using a commercial headset as a platform is that you cannot add a sensor. Eye tracking, biosignals, thermal imaging, an external camera aligned to the display — all of these have to be strapped on, synchronised by hand, and routed over whatever interface is left exposed, usually USB. The result is a pile of latency and a clock-sync problem that eats the project.
A MIPI lane and a PCIe lane, with CAD for the mounting, removes most of that. It is also precisely the kind of affordance that produces work nobody at Valve planned for, which is the stated reason the company has designed this way for years — Hackaday has been pointing at Valve’s hacker-friendly hardware documentation since at least 2020.
Timing
Demand for the Frame currently outstrips supply. If you are on the waitlist, the repository is available now and the design work does not require the hardware in hand — which, given that the STEP models mean you can fit-check in CAD, is most of the work.
The Steam Frame launched on 14 September at $1,059, and the reviews were consistent about comfort and eye-tracked foveated streaming, and equally consistent about the price and the battery.