Open-spec Raspberry Pi CM4 carrier has M.2 and GbE with PoE
Feb 25, 2021 — by Eric Brown 11,625 viewsOratek’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.
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Tofu with CM4 (left) and rear view showing M.2 slot with a Huawei LTE/GPS module
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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.
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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.)
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Tofu detail views
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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.
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