Will Whang's New Raspberry Pi 5 Add-On Brings Support for High-Speed microSD Card Express Storage
"I don't really see a point of using microSD Express card," the maker warns — but has designed a HAT add-on for the cards anyway.
Maker Will Whang, best known for his FourThirdEye and other custom camera modules, has designed an add-on board that gives the Raspberry Pi 5 single-board computer high-speed removable storage: the RPI5-SDexpress-Hat.
"[It's] basically a clone from my CFE Hat project," Whang explains of the add-on storage gadget, "[I] just changed the CF Express socket to SD Express. microSD Express reading speed is indeed faster then microSD card, however its writing speed is more about the same as high-end microSD [...] card[s] (160~200MB/s). Now, you might see some microSD Express advertise for >200MB/s writing speed, but that is not sustained performance; similar to how NVMe [Non-Volatile Memory Express] SSD works, some microSD Express have pSLC [pseudo-Single Level Cell] cache for higher burst write speed. So it make sense as a gaming storage, but I don't see the point for camera recording or any type of high speed recording device given the pricing comparing to standard high-end microSD card/USB flash or M.2 SSDs."
As Whang says, the new storage board is effectively a respin of an earlier project that put a CompactFlash Express slot on top of the Raspberry Pi 5, providing high-speed removable storage which leaves the on-board microSD card slot in the dust. The new variant, brought to our attention by CNX Software, moves away from CompactFlash to microSD Express, now in the mainstream thanks to its support in the Nintendo Switch 2. "In general," Whang warns, "I don't really see a point of using microSD Express card: if you need external storage, M.2 SSD is cheaper; if you need removable storage, M.2 SSD in CF Express Type B is cheaper."
For those hoping to see the microSD Express ecosystem — which effectively ports PCI Express-based high-speed Non-Volatile Memory Express (NVMe) technology to the microSD card form factor — grow and a corresponding price drop in the storage cards, Whang's design provides a way to upgrade any Raspberry Pi 5 to support the new storage devices — though at the cost of tying up its PCI Express lane. In addition to the microSD card Express slot, it also provides a pair of Qwiic-compatible connectors for external hardware — down from the four of the earlier CompactFlash Express version.
Whang has released design files and firmware for the board on GitHub under the permissive MIT license; "I won't do PCBA [Printed Circuit Board Assembly manufacturing] for this board," the maker notes, "because microSD Express card is not there (cost/performance/prevalent) yet."