When the Raspberry Pi Compute Module 4 was released in late 2020, we knew it was destined for embedded server projects. The official Compute Module IO board has all the connectors, but its clunky form factor shows it was never intended to be used in a project. For project use, we need custom carrying boards that break the required connections.
Seeed’s Dual Gigabit Ethernet Carrier Board is compatible with all Raspberry Pi Compute Module 4 boards and is designed to create network devices, file servers and software routers. The inclusion of USB 3.0 is a sweetener for those of us who like to create large, energy-efficient storage devices based on the Raspberry Pi.
Specifications Seeed Dual Gigabit Ethernet Carrier Board
|Networking||Dual Gigabit Ethernet Connectors|
|USB 3.0 to GbE (Gigabit Ethernet Bridge)||Microchip’s LAN7800|
|USB||2 x USB 3.0 ports|
|1 x USB 3.0 9 Pin Header|
|Storage||Micro SD card slot (loading system image for non-eMMC CM4 version)|
|Camera||1 x MIPI CSI Connector|
|Display||1 x MIPI DSI Connector|
|1 x Micro HDMI Connector|
|FPC||Interface for I2C and SPI|
|Flow||5V/3A via USB Type-C port|
|Dimensions||2.95 x 2.5 x 0.8 in (75 x 64 x 21mm)|
Using the Seeed Dual Gigabit Ethernet Carrier Board
Designed for all versions of the Compute Module 4, Seeed’s Dual Gigabit Ethernet Carrier Board is a compact and versatile piece of kit. It has connectors for the Raspberry Pi Compute Module 4, which holds the CM4 in place. Make sure to connect the CM4 properly so that it lays flat on the board and doesn’t hang over one side slightly. The most obvious feature of the board is the dual Gigabit Ethernet ports, LAN0 is connected to the Gigabit Ethernet PHY on the CM4 (a Broadcom BCM54210PE) and LAN1 is connected to a Microchip LAN7800.
The Broadcom Ethernet port is enabled and ready to go, while the other requires a small amount of terminal installation. Next to the Ethernet ports are two USB 3.0 ports, yes we have USB 3.0 ports on the CM4. The official Compute Module IO Board only comes with USB 2.0. Seeed’s board has two USB 3.0 ports broken out of the CM4’s PCIe interface.
Additional USB 3.0 ports can be added via a header, but you must specify your own header breakout. We tested the USB 3.0 speed with an external USB 3 to NVMe drive. Copying a 2.9 GB Raspberry Pi OS image from the NVMe to the CM4’s eMMC took 1 minute 39 seconds. Copying the file to the NVMe drive only took 35 seconds, so we’re confident that the USB 3.0 interface is fast enough to build your own NAS.
Just next to the USB 3.0 header are three pins. PWR, GND and BOOT. Using a jumper wire, we can connect GND and BOOT to force the CM4 into a USB boot mode, which is necessary to flash the OS to the eMMC flash found on some CM4 SKUs. If you have a Compute Module 4 Lite (no eMMC) or prefer to boot from micro SD, there is a microSD card slot on the bottom of the board (see best microSD cards for Raspberry Pi). The interesting thing about this slot is that we have to put the microSD card upside down, something that caught us by surprise.
There are two flat flex connectors on the board. One is for the official Raspberry Pi camera (CSI) and the other for the official display (DSI). We tested both v1.3 and v2.0 of the official cameras with the board and the first problem we encountered was the installation instructions with an incorrect URL. We pulled an alternative from the Raspberry Pi Github repository and tried again. The alternate installation worked in that it downloaded the file to our CM4, but even after enabling and restarting the camera interface via raspi-config, we were unable to take a picture with the camera. We only saw error messages indicating that no camera was present.
After talking to Seeed and flashing a new OS to the eMMC, the error persisted. It turns out that our review unit is an older technical copy with a hardware error. A replacement will be sent to us and we will update the review as soon as we receive it. We couldn’t test the DSI connector for the official display, but we were able to test the micro HDMI output and saw the familiar Raspberry Pi OS desktop. We were also unable to test the I/O FPC, which breaks six GPIO pins, 3v3 and GND via a flat flex connector. The pins broken out include I2C and SPI.
We connected the Seeed Dual Gigabit Ethernet Carrier Board to our bench power supply and saw that on power up, the power draw went to 5.1V at 2.1A and then stabilized to an idle power draw of 800mA at 5.1V. During our stressberry tests we saw the current draw rise to 1.1A and the temperature easily passed the 80 degree Celsius hard thermal gas point, causing the CPU to drop to 1GHz. To cool the CM4 we have a four-pin JST fan connector, compatible with four-pin fans, but keep in mind that this is a 1.25mm pitch four-pin header and not a typical fan connector.
Use Cases for Seeed’s Dual Gigabit Ethernet Carrier Board
The dual Gigabit Ethernet connectors immediately suggest a soft router project and if you have the know-how it can be done relatively easily with Raspberry Pi OS as it is essentially Debian Linux. We can also use the board like a typical Raspberry Pi, just without GPIO.
If we want to create a Pi-Hole DNS box, NAS or media server, the process would be greatly simplified by using Diet-Pi. Diet-Pi is a lightweight, Debian-based distribution with a set of easy-to-use menus that simplify building DNS, file, web, and media servers. We tested Diet-Pi with Seeed’s Dual Gigabit Ethernet Carrier Board and it worked remarkably well.
At $45 plus the cost of your Raspberry Pi Compute Module 4, Seeed’s Dual Gigabit Ethernet Carrier Board is a specialist purchase for those who want or need the dual Gigabit connectors along with USB 3.0.
The whole setup is about the same size as a Raspberry Pi 4, but with Seeed’s Dual Gigabit Ethernet Carrier Board we lose the GPIO. If you’re looking to build CM4-powered servers, this is the current best candidate. If you want a typical Raspberry Pi experience, stick with the Raspberry Pi 4.