An old iPod, a new motherboard and two very different computing jobs
Image: Certain Things / Sprout
The click wheel survives. So does the small monochrome screen. In Sprout, the substantial change is the board hidden behind them: the iPod’s original computing hardware is lifted out and replaced with a design built around Raspberry Pi silicon.
London-based Certain Things is preparing the replacement motherboards for third- and fourth-generation monochrome iPods and the iPod mini. Its campaign is listed as launching soon on Crowd Supply, so this is a project in development rather than a shipping upgrade kit.
The appeal goes beyond adding wireless headphones to an old music player. Retaining the original controls, display and enclosure gives the electronics a set of fixed interfaces to work with. A replacement board has to fit the physical space and drive the parts already there, rather than choose a new screen and controls to suit its own design.
Sprout’s two versions divide that job in different ways. Both use Raspberry Pi’s RP2350 microcontroller. Sprout Pico is intended for local music playback and podcasts; Sprout Pi adds a Compute Module Zero and Linux to support applications and streaming functions. The Pi version is planned for third- and fourth-generation iPods; the mini uses Sprout Pico.
The distinction is substantial. An RP2350 provides microcontroller resources, including programmable I/O for implementing interfaces. Compute Module Zero adds a quad-core Arm Cortex-A53 processor and 512MB of memory. One is a microcontroller; the other supplies the resources of a small Linux computer. They are not interchangeable labels for the same kind of Raspberry Pi board.
Keeping the audio path separate
Certain Things specifies a Cirrus Logic CS43131 audio DAC, although its own comparison page allows for a similar component in the eventual design. The converter feeds the existing 3.5mm headphone connection. Cirrus’s device combines digital-to-analogue conversion with a headphone amplifier, so it addresses the analogue output stage as well as converting the samples.
That matters because playing a music file is not one indivisible task. File access, decoding, user controls and the electrical signal delivered to headphones are different parts of the chain. A processor specification cannot describe the output stage’s performance on its own.
The planned boards also provide Bluetooth audio, Wi-Fi, USB-C charging and data transfer, and microSD storage up to 2TB. Sprout reuses the original screen, click wheel and ribbon cables; the project describes installation without soldering.
Its software is being written to reproduce the familiar wheel-driven interface. For the Pi version, Spotify, Apple Music and AirPlay functions are described as working proofs of concept as of September 2026. Their availability at launch remains dependent on development and the services’ interfaces, rather than being a confirmed capability of a delivered product.
The battery figures are targets too. Certain Things quotes up to 40 hours of continuous Bluetooth playback for the larger iPods with a 2,500mAh cell, based on prototype testing, and 20 hours for the mini with a 1,200mAh cell. These are not claims for every original battery or installation.
The project plans to publish schematics, board layouts and its bill of materials under CERN-OHL-S v2, with firmware and software under MPL-2.0. Its documentation includes reverse-engineering notes for the iPod’s display, click wheel and headphone connectors, with publication promised before the campaign ends.
Sources: Sprout campaign: specifications, prototype status and planned licences; Certain Things: architecture and development qualifications; Raspberry Pi: RP2350 specifications; Raspberry Pi: Compute Module Zero specifications; Cirrus Logic: CS43131 converter and headphone amplifier.
