flops
Posts: 2
Joined: Sun Aug 01, 2021 5:44 pm

CM4 board with WWAN and shared network for laptop

Sun Aug 01, 2021 5:59 pm

Hello, Everyone!

So long story short, i have a laptop with a few space inside for 2.5 SATA drive. There are SATA port and key b m.2 slot with SIM card.
And i thought that i could put there a board with independent battery. If i will remove a few support material i will loose some rigidity and get a few square inches. But still there is a space problem.
Base communications schema is looking something like this:
wwan_base_idea_CM4_v1.png
wwan_base_idea_CM4_v1.png (160.87 KiB) Viewed 457 times
https://drive.google.com/file/d/1iRcyht ... M0ox9/view (mirror link)

The main goals:
1. USB controller with client\host functionality, that i could connect to other PC and use Linux USB gadget api to use it composed HID and network device.
2. WWAN module that will work even when PC is in sleep or powered off and could share this connection with PC.

Optional:
1. External USB port from USB hub connected to PC is optional, but i think it's nice to have a USB A port to be able to connect mouse dongle as most of the USB hubs have 3 ports and Ethernet.
2. Most of WWAN cards are able to use 2 SIM cards at a time, and i already have one slot on a laptops motherboard, as i've found some risers on aliexpress and i thought that this lines could be extended and passed as is to WWAN module. In that case i'll be able to add second SIM when i needed without disassembly laptop.
3. I have mSata drive that i'm currently using just as backup drive for that laptop, in that case i just thought if i will have enough space left i'll just keep it there.
4. NFC is nice to have but there is not much space under keyboard cover so it's just to make some use of i2c\uart from CM4.
5. PCM link is just that i've found identical protocols on CM4 and in most WWAN cards specs. So i thought that it will be possible to make it work even for voice calls.

I've looked on a few SOM boards and one of them is CM4.
The second is Nano Pi Neo Core 2. (In case i wouldn't be able to make xHCI controller at all, but in that case i'll loose a lot of performance).
The main problem is that i need USB controller to be as an external port with possibility to switch between client\host mode. In which I don't see much variations where i can get client functionality with high speeds to be able to share WWAN network with PC. And the most obvious for me became to use Ethernet controller.

Currently i'm trying to make m.2 riser with micro coaxial cable assembly to be able to pass through it from top side motherboard to bottom section for sata drive, the idea came from that article https://habr.com/ru/post/435086/ (sorry it's in russian).

I'm not that good in electronics so i've tried to avoid creating my own IC schemas as much as possible for this kind of speeds.
So i thouth to buy USB 3.0 hub with Ethernet unsolder all ports and use it as is with direct connection to CM4 lines.
USB > UART bridge is CP210x.
For power management as base something like Adafruit 1000C.
The xHCI controller would be a problem for me, but i think i will try to order to do it for me. When i will be sure that idea will work at all.

My open questions for now are:
1. I'm not even sure that ethernet to ethernet on such short distance will work? Or is there another way to connect CM4 to PC without creating a whole custom linux driver?
2. Is there a possibility that i could bypass SIM card lines from m.2 slot for more 15-20cm?
3. What to do with OTG mode power lines? I already have power supply and in client mode the other host will provide power. So i'm not sure how to avoid it. One of my thoughts just cut it from whole circuit and use it only as client. Or are there any other solutions?
4. There are a lot of high speed lines, and i'm ok it to be at least near the max speed of WWAN network. But still i'd like to hear on what i should look to avoid first step mistakes? Specs\articles anything that could help.

Thank you for reading this. I'm sure that my point of view on this project is naive over all levels, cause i'm not familiar how to work with this type of speeds and protocols, but still i will appreciate any help.

aBUGSworstnightmare
Posts: 3460
Joined: Tue Jun 30, 2015 1:35 pm

Re: CM4 board with WWAN and shared network for laptop

Mon Aug 02, 2021 5:35 am

Sorry, but I'm fully ignoring your block diagram after reading your post.

If you want to connect a CM4 to your PC the easiest way is by using this https://geekworm.com/collections/new-ar ... -cm4-stick . There is no way (at least not an easy one) to get access to your PC internal components (i.e. NVME slot).

Image

Can't tell you what's involved for adding the com module to such board (and if that is possible at all), but maybe will give you another pointer to a board designed with cellular communication in mind https://store.oratek.com/products/tofu

flops
Posts: 2
Joined: Sun Aug 01, 2021 5:44 pm

Re: CM4 board with WWAN and shared network for laptop

Mon Aug 02, 2021 8:11 am

aBUGSworstnightmare wrote:
Mon Aug 02, 2021 5:35 am
Sorry, but I'm fully ignoring your block diagram after reading your post.

If you want to connect a CM4 to your PC the easiest way is by using this https://geekworm.com/collections/new-ar ... -cm4-stick . There is no way (at least not an easy one) to get access to your PC internal components (i.e. NVME slot).
I think it's not so difficult if you put the board inside. As i said, i have some space there, to be exact 14cmx8cmx1.7cm.
The SATA lines are already in that space, the problem is to route m.2 slot lines. But if people are extending PCIe it's possible to extend it too into that niche. From the first look the route that i'm going to use doesn't have much energy efficient\noisy elements on it's way. So maybe it will work with appropriate cable.
Sorry if it wasn't that clear in my text. My main goal is to put board inside, connect it to the laptops internal ports and make a few holes in chassis for USB ports i've wanted to use.
About geekworms board, thank you for the find! It's actually close to thing what i'm looking for. But as i can see it routes the same USB lines from USB-AM and USB-AF. In that case you just can't use both ports at the same time. Type-c port is only for power, so there is no way that with this dongle you could connect something while you are connected to PC. And one of my main goals is to connect the CM4 without using the otg port with the protocol that is capable of 40-50Mb\s at least...
aBUGSworstnightmare wrote:
Mon Aug 02, 2021 5:35 am
Can't tell you what's involved for adding the com module to such board (and if that is possible at all), but maybe will give you another pointer to a board designed with cellular communication in mind https://store.oratek.com/products/tofu
Cool board but It's too big :( But it has schematics on github, it will definitely help.
Main issue with commercial boards is that they're trying to route video interfaces (that i have no use) for greater audience coverage. But takes a lot of space that i don't have...
Thank you very much for your time.

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