Project nvme Carrier for the LattePanda Mu

Hello everyone.
Welcome to my project to design a nvme carrier in mini-ITX format for the LattePanda Mu.

 

Motivation and objective

While looking for a not too expensive and small SSD only server I came across the preview nvme carrier for the LattePanda Mu by chance and thought that this would be a nice project.
Originally I had planned to have a board ready by the end of the year to run a private Nextcloud instance on it via Unraid. But during the first attempts to set up a design, I became aware of the LattePanda Mu event, applied and was accepted.
My goal was to develop a two-layer board with six M.2 and two PCIe ports. First of all, it has become a four layer board at this point, but if possible I will deliver a two layer design later.

 

CAD View

 

Overview of the technical data:

Power Input

  * DC 5.5x2.5mm: 12V (Max 10A)
Internal Interfaces
  * 2x PCIe 3.0 x4 (x1 electrical) slot
  * 6x M.2 M Key up to 2280 (PCIe 3.0 x1)
  * CPU and CASE fan socket
  * 1x USB 2.0
  * MOLEX Connector for 5V (2A) and 12V Supply to HDDs
External Interfaces
  * 1x USB 3.2 10Gbps
  * 2x USB 2.0
  * HDMI 2.0
Dimension
  * mini-ITX, 170mm×170mm
Extras
  * Carrier BIOS

 

Considerations for my carrier

The decision to put two PCIe ports on a mini-ITX board and not use a mini-DTX board was purely for aesthetic reasons. Even the mini-ITX format seemed too large for me. However, I wanted to use a reasonable size in order to be able to use normal cases.
Since I didn't want a fixed network interface, but preferred to have a free choice (as far as possible with PCIe x1), I needed at least one PCIe port. A second one would allow more flexibility in the use of the carrier, e.g. a second network card (with several ports), a SATA expansion card or simply another M.2 port via adapter. The reason why I use PCIe x4 slots here is so that slightly larger cards also have more support.
A USB 3.x port was important to me so that I can make local backups to a simple external hard disk, as well as an internal USB 2.0 port for the operating system (in my case Unraid).
I took the external USB 2.0 ports and the HDMI port from the LattePanda Mu Lite Carrier. It's handy to be able to connect a monitor, mouse and keyboard for initial setup or troubleshooting, but otherwise I wouldn't have needed them myself.
The MOLEX connector on the board is intended for the case that someone wants to use the carrier in connection with normal hard disks, as the external power supply does not offer any possibilities for this. However, the design has clear disadvantages with the limited power supply at 5V. Theoretically, it is also possible to connect an internal power supply here.

 

Current status

The carrier is here in front of me and works for the most part.

 

Photos

 

Problems

The biggest time waster on the project was my lack of experience with the PCIe design rules. I had to make several improvements here. There are probably still some design errors or design rules that have been violated, but unfortunately I don't have the time to implement them perfectly. Personally, I'm happy for now if everything works.
At the time of publishing this post, the BIOS is still a problem. Here, for example, it is “not possible” to install the BIOS on the Mu. “Not possible” in the sense of: The required configurations of the HSIO are not adopted, the Lite Carrier configuration remains. Fortunately, I had provided a Carrier BIOS. Here the installation works via CH341A (moddet to 3.3V!!!). However, there seem to be problems here too. The USB 3.x port only works with USB 2.0 devices and if HSIO6 is not used, nothing is recognized on the HSIO2. There may be other combinations that do not work. I still have to test this.

There are still a few errors in the design:
1. the ground PIN of the internal USB 2.0 port hinders the installation of an M.2 SSD (from 2242) on the second port
2. the mounting PINs of the PCIe ports prevent the installation of a 2280 M.2 SSD on port 6
3. the mounting holes for the Mu are slightly offset

 

I will correct point 3 in the next few days.
Points 1 and 2 can be fixed with a side cutter for the time being, but will be addressed in the design. I will move the USB port and replace the PCIe ports with SMD versions.

 

Files

Everything from me can be found on GitHub. The CAD data is available in a Fromat for KiCad. (I still have to clean up a bit as much of the Lite Carrier has been taken over)
The BOM list is the same as when I ordered the board for myself.
I will deliver the BIOS as soon as I have received a short written authorization.

 

If anyone has suggestions for improvement or ideas for my carrier, you are invited to discuss them here and/or on GitHub.