Exploring the TOFU Raspberry Pi CM4 Development Board

In the latest issue of Custom PC magazine, Gareth Halfacree reviews Oratek’s TOFU, a dedicated development board for the Raspberry Pi CM4.

Launched last year, the Raspberry Pi CM4 series has sparked a design boom in development boards, largely due to the Raspberry Pi Foundation’s decision to release its own circuit designs, allowing others to break free from limitations and create their own.

The Tofu is cleverly designed and powerful, making it an excellent development board for the Raspberry Pi CM4.

Oratek does not hide its inspiration; it aims for industrial applications, but with friendly additional features, it can also be used by enthusiasts seeking compact, complete solutions to connect many I/Os of microcontrollers.

In use, the magnets are a bit weak, and besides tightening the screws in the corners, there is no other way. Otherwise, it is a well-designed case with ventilation on the top and bottom. Unfortunately, this is not enough to prevent the Compute Module 4 from reaching its thermal throttling point under sustained heavy loads, so you will need to purchase third-party cooling or fan accessories.

The 90 x 90mm circuit board expands many functions, including a gigabit Ethernet port that supports PoE on the right side, two USB 2 Type-A ports, a barrel jack, and a 3.5mm power port that supports 7.5V~28V. These inputs are routed to internal connectors that require more power than the 40-pin GPIO can provide for attachments. Meanwhile, there is a 22-pin connector on the bottom for CSI and DSI peripherals, a full-size HDMI port, and a USB 2.0 port.

Both the top and bottom can be rotated for easy connections.

The left side includes a micro-SD slot for Compute Module 4 variants without onboard eMMC storage, and a micro-SIM slot—hinting at another feature that becomes visible once the circuit board is flipped. There is also a USB Type-C port for programming or as an On-The-Go (OTG) port.

Flipping the circuit board reveals the purpose of the micro-SIM slot. The CM4’s PCI-E lanes connect to the M.2 B-Key slot, providing connections for other hardware, including 3G/4G modems. For storage, you can use an adapter board to convert it to M-Key for NVMe devices, with spacers for drives in 2230, 2242, 2260, or 2280 form factors.

The Tofu has many ports, but no USB 3.0.

Unfortunately, this is not as flexible as it sounds. The spacers are soldered in place and must be chosen at the time of ordering; if you want to switch to a different size drive, you will need another adapter.

Another standout design point of the Tofu: a replaceable fuse, a Littelfuse Nano 2 3.5A device originally designed for automotive projects, primarily for protection but also allows you to cut off the onboard power when powering the board via PoE. Once the fuse is in place, you can clearly hear the coil humming, which can be eliminated by carefully popping the fuse out of its holder. If you stop using PoE, remember to put it back in place.