daughter board for cm4 module in cm3 place

[Mikeynl]

Hi Guys,

We have nice products based on cm3.

With the new cm4, we have two choices. Refactor all products to fit cm4 and move forward. Or looking out for options to make a daughter board that fits in the sodim and there cm4 on top. And maintain the line-up for now as it it. We prefer the daughter board road. More because of the new added features we dont need.

Would like to share any ideas etc etc.

[cleverca22]

one option, would be to route the new/unused stuff (2nd hdmi, pcie, ethernet) to some connectors on the daughter board, and then route the rest back to the old sodimm edge

then you can still use the new stuff if you want to, or not populate those connectors on some variants of the daughter board

the ethernet for example could be useful even in existing designs, just plug your cable in a different spot and ignore the old controller

[Mikeynl]

one option, would be to route the new/unused stuff (2nd hdmi, pcie, ethernet) to some connectors on the daughter board, and then route the rest back to the old sodimm edge

then you can still use the new stuff if you want to, or not populate those connectors on some variants of the daughter board

the ethernet for example could be useful even in existing designs, just plug your cable in a different spot and ignore the old controller

If you do that, you also need to do new usb on daughter board. For us only routing the stuff we need and maybe add tpm chip on it. Get it working is prio 1, adding extra's can also be an option. We have some space and it give for sure new options (if needed)

[Mikeynl]

On the new module there is a need of 5V. We allready have 5v in the design with a TPS54540DDA. So the daughter board will have at least two wires.

[scotty101]

Since the CM4 will be available until 2028, I'd say it is worth the effort to refactor existing products.

[Mikeynl]

Since the CM4 will be available until 2028, I'd say it is worth the effort to refactor existing products.

If we do that, and start making new boards. It means when an old board gets broken we have to replace board and module. With daughter board we dont have this issue

[trejan]

What GPIOs does your board use? The CM4 no longer brings out GPIO30-57 as they're all used for onboard peripherals. If your board needs those GPIOs and you can't swap then you can't use a CM4.

[jamesh]

Since the CM4 will be available until 2028, I'd say it is worth the effort to refactor existing products.

If we do that, and start making new boards. It means when an old board gets broken we have to replace board and module. With daughter board we dont have this issue

Build up a stock of older devices for the replacement use case?

I don't believe we have plans for a convertor board.

[rpiMike]

CM4 to CM3 adapter board:

https://store.gumstix.com/manufacturer/ ... uprev.html

[jamesh]

CM4 to CM3 adapter board:

https://store.gumstix.com/manufacturer/ ... uprev.html

That was quick!

[gsh]

There's lots of companies who had early access to the CM4 for development purposes

[Mikeynl]

What GPIOs does your board use? The CM4 no longer brings out GPIO30-57 as they're all used for onboard peripherals. If your board needs those GPIOs and you can't swap then you can't use a CM4.

with updated dts and new routed pins, dont think that will be a problem

[Mikeynl]

CM4 to CM3 adapter board:

https://store.gumstix.com/manufacturer/ ... uprev.html

Just saw this on my timeline too. So its possible. We will make a custom one anyway.

[Mikeynl]

Since the CM4 will be available until 2028, I'd say it is worth the effort to refactor existing products.

If we do that, and start making new boards. It means when an old board gets broken we have to replace board and module. With daughter board we dont have this issue

Build up a stock of older devices for the replacement use case?

I don't believe we have plans for a convertor board.

You guys believe in backwards compatibility, so do we. Keeping old stock is not the best option in sooo many ways

[trejan]

CM4 to CM3 adapter board:

https://store.gumstix.com/manufacturer/ ... uprev.html

Some weirdness with that design. It is a mixture of trying to make the CM4 backwards compatible but also they've made multiple changes that would require a new motherboard. I guess it does make the CM4 a bit more friendly for people building boards with a hotplate since aligning the two connectors can be tricky.

They've broken out the onboard Ethernet to what is meant to be the SD interface pins so you can't use this with a CM4 Lite. The NC pins have been repurposed for PCIe. The composite output pin is used for an Ethernet LED. One pin of the VC JTAG interface is the other Ethernet LED but the rest of the VC JTAG interface is NC. CM4 no longer breaks out GPIO30-GPIO45 as they're used onboard so this adapter has a 16 channel I2C expander to replace them.

[cleverca22]

CM4 to CM3 adapter board:

https://store.gumstix.com/manufacturer/ ... uprev.html

Some weirdness with that design. It is a mixture of trying to make the CM4 backwards compatible but also they've made multiple changes that would require a new motherboard. I guess it does make the CM4 a bit more friendly for people building boards with a hotplate since aligning the two connectors can be tricky.

They've broken out the onboard Ethernet to what is meant to be the SD interface pins so you can't use this with a CM4 Lite. The NC pins have been repurposed for PCIe. The composite output pin is used for an Ethernet LED. One pin of the VC JTAG interface is the other Ethernet LED but the rest of the VC JTAG interface is NC. CM4 no longer breaks out GPIO30-GPIO45 as they're used onboard so this adapter has a 16 channel I2C expander to replace them.

ah, yuck!
i would have broken all of the new stuff out to new connectors, and left the old 30-45 pins unconnected, so its functionally identical, but some gpio "dont work"