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Timebeat's TimeCard Mini Turns a Raspberry Pi Compute Module 4 Into a Nanosecond-Capable Clock

Designed to sit between a CM4 module and the IO Board, the Timecard mini keeps the full 40-pin GPIO header free for more hardware.

(Original article written by Gareth Halfacree for and can be found here)

British high-precision timing specialist Timebeat has launched an interposer board for the Raspberry Pi Compute Module 4 (CM4) dubbed the TimeCard mini — providing a compact footprint for temperature-corrected global navigation satellite system (GNSS) time server projects.

"With this module," the company claims of its creation, "you can turn your Raspberry Pi into a nanosecond-capable grandmaster clock without any prior knowledge. These units have even been deployed in submarines and rockets that go into space!"

The board's design came out of work carried out by the Open Compute Project's Time Appliances Project (TAP), which sought to promote industry collaboration on high-accuracy timing devices for use in the data center and further afield. While Timebeat's previous hardware devices have focused on server use, the TimeCard mini is its first compact design for the Raspberry Pi Compute Module 4 (CM4) system-on-module.

The Timebeat TimeCard mini is a smart interposer design, which adds nanosecond-capable timing to the Raspberry Pi CM4 (📷: Timebeat) The TimeCard mini board features high-density connectors to mate with the CM4 module and connect it to an on-board u-blox MAX M10s GNSS receiver module with temperature-controlled oscillator. It's not designed for stand-alone use, however: rather than being a carrier board, it's an interposer design that sits between the CM4 module and the official Raspberry Pi Compute Module 4 IO Board carrier — leaving, the company points out, the 40-pin general-purpose input/output (GPIO) header free for other hardware. Connectors are provided for an external antenna, pulse-per-second (PPS) input and output signals, and a 10MHz oscillator signal — while two module slots provide room for future expansion.

Timebeat is selling the TimeCard mini on its Tindie store at $65 including u-blox MAX M10s but excluding Raspberry Pi CM4 module and IO Board; variants with u-blox LEA M8S and M8F receivers are available at a $150 and $250 premium respectively.

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