Will the RAK2247 work with the new Raspi Compute 4?

I see the new raspi compute 4 I/O module has a PCI-e slot.
Can anyone suggest if that will work with the RAK2247 module?

Hi @marthough,
It has to work fine, just make sure to select the SPI variant when ordering RAK2247. You may need to change the pin mapping in the software.

Hei Guys,

Are you sure?
The Pi4 Compute module has a PCIe, RAK2247 has mPCI.
These are supposed to be different physically, right ?

Regards
Vladislav

Raspi compute module 4 (as previous versions of Raspi compute) is not a user ready product. It needs to be plugged into a carrier board that provides additional power and gpio circuitry.

So that board needs to route the SPI signals from the RAK2247 mPCIE connector to the corresponding SPI gpio signals of the CM4 on its high density connector.

Short answer: RAK2247 works with RPI CM4, but you need a specifically designed board to do that.

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Hei @alnunez,

We were actually talking about that specific carrier board that is the Compute Module 4 IO Board.

@Hobo is absolutely right. @marthough you will need similar converter board https://techship.com/products/mpcie-pcie-adapter-mini-size/ to use RAK2247 with the PCIe connector. As the I/O board have standard RPi 40 pins connector you can use it with RAK2247 PiHAT https://store.rakwireless.com/products/rak2247-pi-hat?variant=36031289688222

AFAIK RAK2247 only uses mPCIE as mechanical and power interfaces, but uses SPI for signals, so even if that board (or other boards) have mPCIE slots, it doesn’t means automatically supports RAK2247 module in SPI mode.

USB mode is other story, but is discouraged by Semtech due to low performance reasons.

Yes, it will involve a lot of work :slight_smile: to make it running with the compute module or with the IO board that way. The PiHAT for RAK2247 and IO board is the best approach for this.

Hey RAKstars @velev @Nikola @Hobo:

A Pi4 Compute module with eMMC would provide an awesome level of power & flexibility for a new generation of WisGate Edge don’t you think?

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Yes, I believe it would :slight_smile:

You had me at Yes.

Where do I send the money?

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This detail the eMMC is critical. Raspi’s are fun but that sd card is deadly for any industrial or commercial application. Therefore the pihat isn’t for me. Really intelligent sensors, for commercial applications with local logic to handle events, control outputs without waiting for uplinks and downlinks - then report their status and metrics on a regular basis is where I want to go with this.

Thats good to hear anyway. I won’t rush out to test this, but I can see anyone who can get a LoRa concentrator onto that PCIe slot will have a winner winner.

Well there is a 40pin header so you can just use a Pi HAT I suppose :wink: for that LoRa magic.

To get the benefit eMMC of CM4 quickly, the best approach is to use the pi Hat for RAK2247 then the IO board of CM4.

Also, the CM4 IO board design is available in Kicad so anyone can modify it freely. Even a bare RAK2247 can be used if you redesign the IO board with mPCIE for RAK2247 :wink:

It’s the reverse with the Compute modules - you have to ADD an SD Card interface.

The Pi4 Compute module, like most of the Pi Compute modules, come with eMMC on board (as long as you buy one with > 0GB of eMCC as there is a model without any.

And a gateway isn’t a “really intelligent sensor”, it’s a gateway.

I have TinyML running on a Trinket M0 which relays data via RAK4200 when vibrations hit a certain model. Plus a raft of devices that can do all sorts of things - this was a solved problem a long while back - you just create a design, add code & test, rinse & repeat and one day soon, you get a pretty complex state driven device - certainly more intelligent than some people I know.

Absolutely.

But eventually, it would be nice to have a small compact gateway that doesn’t come with all the other cruft the IO board brings to the party.

Not that I went to bed late last night due to looking at the details much.

To be clear, what’s needed is not really mPCIe, but rather an mPCIe connector with the additional non-standard routing of SPI signals to it on the same pins that RAK uses for that purpose. One might as well also route USB signals to support either some version of the Semtech PicoGW reference design (RAK should consider offering one!) or legacy FT2232 solutions. The actual PCI signals aren’t really of any particular use.

Then, given how many compact gateways are going to need mobile backhaul, it really makes sense to place not one mPCIe connector, but two, with the modem one primarily so needing the embedded USB. Then given quirks in some modems, route each slot’s power through a power switch chip controlled by the SoC so that they can be cold booted.

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