when. . .when Raspberry Pi Computing Module 4 Released at the end of 2020, we know it is for embedded server projects. The official computing module IO board has all the connections, but the clumsy shape shows that it was never intended to be used in the project. For project use, we need a customized carrier board to disconnect 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 equipment, file servers, and software router applications. The addition of USB 3.0 is a sweetener for those of us who are eager to create low-power, large-scale storage devices based on Raspberry Pi.
Seeed Dual Gigabit Ethernet Carrier Board Specifications
|networking||Dual Gigabit Ethernet connector|
|USB 3.0 to GbE (Gigabit Ethernet Bridge)||Microchip’s LAN7800|
|USB||2 USB 3.0 ports|
|1 x USB 3.0 9-pin connector|
|Store||Micro-SD card slot (load system image of non-eMMC CM4 version)|
|camera||1 x MIPI CSI connector|
|exhibit||1 x MIPI DSI connector|
|1 x Micro HDMI connector|
|Soft board||I2C and SPI interface|
|strength||5V/3A use USB Type-C port|
|aspect||2.95 x 2.5 x 0.8 inches (75 x 64 x 21 mm)|
Use Seeed Dual Gigabit Ethernet Carrier Board
Seeed’s dual Gigabit Ethernet carrier board is designed for all versions of computing module 4. It is a compact and versatile kit. It has a connector for Raspberry Pi Compute Module 4 to hold the CM4 in place. Make sure to connect the CM4 in the correct way so that it is flush with the circuit board and does not hang slightly on one side. The most obvious feature of this board is the dual Gigabit Ethernet ports, LAN0 is connected to the Gigabit Ethernet PHY on CM4 (Broadcom BCM54210PE), and LAN1 is connected to Microchip LAN7800.
The Broadcom Ethernet port is enabled and ready for use, and the other requires a few settings from the terminal. Next to the Ethernet port are two USB 3.0 ports, yes, we have USB 3.0 ports on the CM4. The official computing module IO board only comes with USB 2.0. Seeed’s motherboard has two USB 3.0 ports, separated from the CM4 PCIe interface.
You can add additional USB 3.0 ports through the connector, but you need to provide your own breakout for the connector. We tested the USB 3.0 speed using an external USB 3 to NVMe drive. It takes 1 minute and 39 seconds to copy the 2.9GB Raspberry Pi OS image from NVMe to eMMC of CM4. It only takes 35 seconds to copy the files back to the NVMe drive, so we believe that the speed of the USB 3.0 interface is enough to build your own NAS.
Next to the USB 3.0 connector are three pins. PWR, GND and BOOT. Using jumpers, we can connect GND and BOOT to force CM4 to enter USB boot mode to flash the operating system to the eMMC flash memory on some CM4 SKUs.If you have Compute Module 4 Lite (without eMMC) or prefer to boot from micro SD, there is a microSD card slot at the bottom of the board (see The best microSD card for Raspberry Pi). The interesting thing about this slot is that we need to insert the microSD card upside down, which caught us off guard.
There are two flat flexible connectors on the board. One is for the official Raspberry Pi camera (CSI) and the other is for the official display (DSI).We tested the v1.3 and v2.0 of the official camera with the motherboard. The first problem we faced was that the URL of the installation instructions was incorrect. Raspberry Pi Github Repository and try again. Alternative installation works by downloading files to our CM4, but even after enabling the camera interface via raspi-config and restarting, we cannot use the camera to take pictures. All we see is an error message indicating that the camera does not exist.
After talking to Seeed and flashing the new operating system to eMMC, the error persisted. It turns out that our review unit is an older engineering sample, and it has hardware errors. An alternative is being sent to us, and we will update the review once we receive it. We were unable to test the DSI connector of the official display, but we were able to test the micro HDMI output and saw the familiar Raspberry Pi OS desktop. We also cannot test the I/O FPC that disconnects six GPIO pins, 3v3 and GND through a flat flexible connector. The disconnected pins include I2C and SPI.
We connected the Seeed dual Gigabit Ethernet carrier board to our workbench power supply, and saw that the power consumption reached 5.1V, 2.1A at startup, and then stabilized to 800mA idle power consumption when 5.1V. In our stress berry test, we saw that the current consumption rose to 1.1A, and the temperature easily exceeded the hard thermal throttling point of 80 degrees Celsius, which dropped the CPU to 1 GHz. To cool the CM4, we have a four-pin JST fan connector, which is compatible with four-pin fans, but please remember that this is a four-pin 1.25mm pitch connector, not a typical fan connector.
Seeed’s dual Gigabit Ethernet carrier board use case
The dual Gigabit Ethernet connector immediately suggests a soft router project. If you have expertise, this can be done relatively easily with Raspberry Pi OS, because its core is real Debian Linux. We can also use this board as a typical Raspberry Pi, but there is no GPIO.
If we want to make Pi-Hole DNS box, NAS or media server, then using Diet-Pi can greatly simplify the process. Diet-Pi is a lightweight distribution based on Debian. It has a series of easy-to-use menus that simplify the construction of DNS, file, Web, and media servers. We tested the Diet-Pi using Seeed’s dual Gigabit Ethernet carrier board and it worked very well.
At only $45 plus the cost of Raspberry Pi Compute Module 4, Seeed’s dual Gigabit Ethernet carrier board is specifically purchased for those who want or need dual Gigabit connectors and USB 3.0.
The entire setup is roughly the same size as the Raspberry Pi 4, but with Seeed’s dual Gigabit Ethernet carrier board, we lose the GPIO. If you want to build a CM4-driven server, then this is the best choice right now. If you want a typical Raspberry Pi experience, stick to Raspberry Pi 4.