Mikeynl
Posts: 45
Joined: Sat Nov 11, 2017 1:36 pm

daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 11:53 am

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
Posts: 2397
Joined: Sat Aug 18, 2012 2:33 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 12:02 pm

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
Posts: 45
Joined: Sat Nov 11, 2017 1:36 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 12:05 pm

cleverca22 wrote:
Mon Oct 19, 2020 12:02 pm
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
Posts: 45
Joined: Sat Nov 11, 2017 1:36 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 12:23 pm

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
Posts: 4153
Joined: Fri Jun 08, 2012 6:03 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 1:43 pm

Since the CM4 will be available until 2028, I'd say it is worth the effort to refactor existing products.
Electronic and Computer Engineer
Pi Interests: Home Automation, IOT, Python and Tkinter

Mikeynl
Posts: 45
Joined: Sat Nov 11, 2017 1:36 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 2:49 pm

scotty101 wrote:
Mon Oct 19, 2020 1:43 pm
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
Posts: 3062
Joined: Tue Jul 02, 2019 2:28 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 3:36 pm

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
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 27729
Joined: Sat Jul 30, 2011 7:41 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 3:54 pm

Mikeynl wrote:
Mon Oct 19, 2020 2:49 pm
scotty101 wrote:
Mon Oct 19, 2020 1:43 pm
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.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed.
I've been saying "Mucho" to my Spanish friend a lot more lately. It means a lot to him.

User avatar
rpiMike
Posts: 1609
Joined: Fri Aug 10, 2012 12:38 pm
Location: Cumbria, UK

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 4:01 pm


jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 27729
Joined: Sat Jul 30, 2011 7:41 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 4:03 pm

rpiMike wrote:
Mon Oct 19, 2020 4:01 pm
CM4 to CM3 adapter board:

https://store.gumstix.com/manufacturer/ ... uprev.html
That was quick!
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed.
I've been saying "Mucho" to my Spanish friend a lot more lately. It means a lot to him.

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1629
Joined: Sat Sep 10, 2011 11:43 am

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 4:05 pm

There's lots of companies who had early access to the CM4 for development purposes
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

Mikeynl
Posts: 45
Joined: Sat Nov 11, 2017 1:36 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 4:29 pm

trejan wrote:
Mon Oct 19, 2020 3:36 pm
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
Posts: 45
Joined: Sat Nov 11, 2017 1:36 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 4:30 pm

rpiMike wrote:
Mon Oct 19, 2020 4:01 pm
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
Posts: 45
Joined: Sat Nov 11, 2017 1:36 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 4:31 pm

jamesh wrote:
Mon Oct 19, 2020 3:54 pm
Mikeynl wrote:
Mon Oct 19, 2020 2:49 pm
scotty101 wrote:
Mon Oct 19, 2020 1:43 pm
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
Posts: 3062
Joined: Tue Jul 02, 2019 2:28 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 4:37 pm

rpiMike wrote:
Mon Oct 19, 2020 4:01 pm
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
Posts: 2397
Joined: Sat Aug 18, 2012 2:33 pm

Re: daughter board for cm4 module in cm3 place

Mon Oct 19, 2020 4:40 pm

trejan wrote:
Mon Oct 19, 2020 4:37 pm
rpiMike wrote:
Mon Oct 19, 2020 4:01 pm
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"

Return to “Compute Module”