The Switchberry Turns a Raspberry Pi Compute Module 4 Into a Time-Focused Ethernet Switch

San Jose-based TimeAppliances has designed a Raspberry Pi Compute Module 4 carrier with a difference: it turns the popular computer-on-module into a five-port gigabit layer-two switch, with support for synchronous Ethernet and the Precision Time Protocol (PTP).

"Switchberry is a Raspberry Pi [Compute Module] 4–controlled Ethernet switching + timing platform built around a Microchip KSZ9567 and a Renesas 8A34004 clock-matrix DPLL [Digital Phase-Locked Loop]," TimeAppliances says of its creation. "It's designed for PTP [Precision Time Protocol]/SyncE [Synchronous Ethernet]/timing lab workflows while staying flexible enough to run as a compact managed switch/router with precise timing I/O [Input/Output]."

A look at the front of the Switchberry would have you think it's just a straightforward gigabit Ethernet switch, were it not for the ventilation cut-outs resembling a speeding clock at the top: there are five RJ45 ports, ready for cabling. Turn it around, though, and you've got ports you wouldn't normally expect: a microSD Card slot for the operating system, a microHDMI port for video and audio, and five SMA connectors — four for connection to external devices with built-in multiplexing for configurable input/output options, and the fifth for an optional GPS receiver for precision timing when used with an OCP M.2 slot, with a second M.2 slot supporting optional Wi-Fi radio modules.

Timing, in fact, is the Switchberry's raison d'être: by default, the device acts as a plug-and-play Layer 2 unmanaged gigabit switch, but with Precision Time Protocol (PTP) enabled — forwarding PTP packets with hardware residence-time correction. Synchronous Ethernet can also be enabled, acting as either an end-point or boundary clock — while PTP operation can be configured for grandmaster or client modes, with the transparent forwarding behavior overridden for DSA kernel architecture mode.

If that all sounds like gibberish, you're probably not in the device's target market: TimeAppliances designed the Switchberry for use in timing-sensitive network operations, for transparent clock provision and experimentation, satellite-time referencing, clocking experiments, and the like.

The Switchberry is listed on Tindie at $999, though at the time of writing was showing as out-of-stock; design files and software sources are available on GitHub under the Creative Commons Attribution-NonCommercial 4.0 International license.