Exploring the Potential of Embedded Core Boards

I am Lao Wen, an embedded engineer who loves to learn.

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As an amateur embedded engineer, my main job is to use microcontrollers to detect different button actions and implement various LED light effects (advanced lighting). Occasionally, I also design some circuit boards to validate ideas or technical solutions.

Small modules I have made before.

While taking a break, I also enjoy tinkering with embedded Linux development boards. After all, my technical skills cannot always be limited to buttons and lights; I need to tackle some high-end technologies. I have tested many Linux development boards and have gained considerable insights into setting up development environments, which can be reviewed via the links below.

Embedded software and hardware development relies on excellent documentation!

【Embedded AI】Setting up a development environment, which discourages many beginners?

The Apple iPhone 16 has been released; how high is the degree of localization for embedded HarmonyOS?

High-end technologies often require high-end hardware for perfect support. Upon careful observation, I found that the development boards I tested were designed using the 【core board + base board】 approach.I am curious, why use this modular design instead of directly mounting the CPU onto the circuit board?

For example, this FET3588-C core board from Feilin has the CPU, memory, and eMMC made as a core board, using a 10-layer gold-plated process, measuring 68mm * 50mm, and a thickness of 1.6mm.

For an introduction to this core board, you can click the link below to learn more.

Today’s embedded ARM chips are becoming increasingly powerful!

To cover the front and back of such a small circuit board with chips and components while exposing most of the CPU pins for engineers to use, and still keep it so thin, how do they manage to do it?

Exploring the Potential of Embedded Core Boards

(This core board has an impressive performance, featuring an 8-core Cortex-A architecture and equipped with a 6TOPS NPU, making it very suitable for embedded AI applications, especially in machine vision and AI multimedia processing fields.)

I also searched online and found that many similar desktop mini-computers generally have their CPUs directly laid out on the circuit board, with the entire board using at least 8 layers of PCB, paired with an industrial CNC case that looks really good.

Leaving this Feilin core board to gather dust is indeed a waste, so on a sudden impulse, I somewhat recklessly thought about matching it with a base board (a semi-finished product, not wired yet)…

This base board mainly provides the power supply circuit for the core board, debugging serial port, USB interface, SD card interface, RTC clock circuit, and is equipped with several user buttons and a cooling fan interface.

Since I also want to consider aesthetics later, the base board’s area has to be controlled to within 10cm * 10cm and cannot be too thick.

(Another reason is that samples exceeding 10cm * 10cm are no longer free and can cost several hundred dollars, but it seems that Jialichuang has now halved the cost of the second sample, being poor, I can’t afford this sampling fee~

)

After laying out the base board, I found that the design was not perfect; the space on the left side of the base board could still accommodate network and HDMI interfaces, and I could add a Bluetooth module (for keyboard and mouse). With network and HDMI, it would become a small desktop computer~

Suddenly adding HDMI and wired network interfaces increased the number of components significantly, I felt that a 4-layer board was no longer sufficient for routing; I need to upgrade to a 6-layer board, and I can also try to further reduce the size of the base board.Honestly, the square appearance design is quite ugly~

After upgrading to a 6-layer board, to better solve the problem of routing in a small space, I used the blind via process, meaning vias are drilled on pads to reduce routing. There’s no need to worry about soldering issues; the blind via uses resin plug + electroplated cap method, ensuring that the surface of the finished PCB’s pads is flat, without seeing via holes. Currently, Jialichuang offers this process for free for 6-layer boards, and sampling is still free.

Blind via process demonstration, source: Jialichuang

(It is understood that the engineering fee for sampling a 6-layer board at Jialichuang has been reduced from 400 to 200, directly halving the cost. Even if multiple samples are made within a month, significant savings can be achieved!)

This mini desktop computer has powerful performance, capable of running Linux operating systems as edge servers, and can also run Android systems with rich multimedia applications. The built-in NPU can perform offline AI model calculations, making it highly versatile!

At this point, I seem to understand that separating the core board is actually a consideration by the development board manufacturers based on practical applications, balancing cost, usability, and stability.

If the CPU, memory, and eMMC components were all mounted on the base board, the cost of hardware expansion later would be very high, essentially requiring a complete redesign of the entire PCB.

However, if the design adopts the 【core board + base board】 approach, only the base board needs to be redesigned, and the number of layers in the circuit board doesn’t have to be so many~

No more talking, I need to start wiring; I might need to ask Jialichuang for help with the PCB layout, as a 6-layer board is indeed a bit challenging for me~

True. High multi-layer PCB

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