Open-spec Raspberry Pi CM4 carrier has M.2 and GbE with PoE

Open-spec Raspberry Pi CM4 carrier has M.2 and GbE with PoE

Feb 25, 2021 — by Eric Brown

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Oratek’s $110 “Tofu” carrier for the RPi CM4 is equipped with GbE with PoE, HDMI, 3x USB, Type-C, MIPI DSI- and CSI, 7.5-28VDC input, and M.2 with micro-SIM and NVMe support.

The Oct. 2020 launch of the Raspberry Pi Compute Module 4, which lacks pin compatibility with the RPi CM3, has attracted a new wave of companies selling carrier board alternatives to the official $35 carrier. The latest is Switzerland based Oratek, which has opened pre-orders for a Tofu board for 99 Swiss Francs (about $110), with shipments due in mid-March. The board ships with schematics, mechanical drawings, a STEP file, and other open hardware resources.

Tofu with CM4 (left) and rear view showing M.2 slot with a Huawei LTE/GPS module
(click images to enlarge)

Whereas some CM4 carriers focus on specific features such as cameras, storage, or robotics, the Tofu is a more general-purpose, high-end carrier for industrial applications. Like the $130 Gumstix Raspberry Pi CM4 Development Board, the Tofu provides an M.2 slot, and unlike that board it adds a micro-SIM slot. The crowd-sourced, $134 Over:Board Mini-ITX carrier instead opts for a full-size PCIe card.

Other, more affordable, CM4 carriers lack PCIe expansion of any kind. These include Sourcekit’s $14.50 PiTray mini, as well as other Gumstix carriers, including a Gumstix Raspberry Pi CM4 PoE Smart Camera board that like the Tofu provides GbE with PoE. There is also an upcoming Wiretrustee SATA Board for Raspberry Pi CM4 and a Piunora carrier, which will offer an M.2 slot. Meanwhile, Seeed is working on a CM4 carrier and can help you design and manufacture your own design with its Seeed Fusion PCB Assembly Service.

The Raspberry Pi Compute Module 4 switched to dual (low speed and high speed) 100-pin connectors, enabling a smaller 55 x 40mm footprint than the CM3. The $25 to $90 module has the same Broadcom BCM2711 SoC with 4x 1.5GHz Cortex-A72 cores used by the Raspberry Pi 4.

The CM4 module ships with 2GB to 8GB LPDDR4-3200 RAM and 0GB to 32GB eMMC. There is a GbE controller with PoE support, optional 802.11ac with BT 5.0, and new support for dual 4K HDMI ports and PCIe 2.0. Other features include 2x and 4x MIPI-DSI and -CSI interfaces.

The 90 x 90mm Tofu, which we saw on Tom’s Hardware, is equipped with a microSD slot and 3x USB 2.0 host ports. (The CM4 sacrifices the RPi 4’s USB 3.0 support to enable PCIe.)

Tofu detail views
(click images to enlarge)

The carrier board features ESD protection on its PoE-enabled GbE port, full-sized HDMI port, and USB Type-C port. There are also 22-pin MIPI-DSI and MIPI-CSI connectors, with optional ribbon cables, as well as a 40-pin GPIO connector.

The M.2 B-key 2242 slot supports SSDs including NVMe modules (128GB KingSpec and Western Digital NVMe SSDs have been tested), and the micro-SIM slot enables wireless connections. Several Huawei and Sierra Wireless 4G LTE/GPS modules have been tested.

The carrier board features dual 7.5 to 28VDC inputs via a jack and a terminal block. There is also an input voltage breakout, which despite the name, is intended primarily as an output for powering HATs loaded via the board’s 40-pin connector. The breakout can be used for input, but it lacks the reverse polarity protections of the standard power inputs. The Type-C port can also handle power input but cannot power M.2 modules.

Other features include LEDs, mounting holes, and an eMMC boot jumper. Reduced feature customizations are available on 200+ orders.

Further information

The Tofu is available for 99 CHF ($110), and 11 CHF for a MIPI cable, with shipments due in mid-March. More information may be found product/shopping page and the wiki.