Imre
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Expandable baseboard (slot system) for CM3

Sun Jul 16, 2017 2:10 pm

Hi Everyone!

First of all, I didn't want to open an 'n+1' topic, but I could not find any definitely similar one. Of course, there are similar topics, but I found them rater focusing on making 'only' parallel Pi platforms, not 'distributed' systems consisting different hardware components.

It is my old plan to buid a homebrew computer system in a modular way. It came into picture time by time, but I never found any feasible idea witch needs only an 'acceptable' amount of effort to implement.

I found homebrew CPU projects on the internet, even built up with discerete transistors. These are wery interesting, but not exactly meet my concept (mainly 8 bit only, huge amount of work, limited useability and lack of software resources).

Building a (modular) computer platform (not at transistor level, of course) is a thing what I am interested in, but writing a bunch of softwares for it is not my world.

That's why I am happy for the CM3 witch seems to be powerful enough and have very wide community from software side.

My plan briefly:
- creating a baseboard with DDR2 SODIMM sockets
- sockets can be populated with one or more CM3s, memory modules, or with custom boards (for any kind of purposes)
- inteconnecton between the SODIMM sockets will be realized by FPGAs to make it flexible

It is very important to emphasis that this 'project' doesn't have any definite purpose. It is just for fun and pleasure. Nothing more. :)

Are there anybody here who is also interested in (at least a little bit) this kind of project?

Imre
Last edited by Imre on Sun Jul 16, 2017 7:30 pm, edited 1 time in total.
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

W. H. Heydt
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Re: Expandable baseboard (slot system) for CM3

Sun Jul 16, 2017 3:49 pm

Item one...while the connector for a CM3 is physically the same as an SODIMM connector, it is not electrically compatible. In any given slot, you would only be able to put in either a CM3 or a DDR module without a *lot* of work (the board would have to be able to identify what was inserted--without powering it up incorrectly--and a change how that slot was treated). The next point is: Why memory units? The CM3s can't use them. The VC4 that is part of the BCM2837 can only address 1GB RAM, and that RAM is already on the CM3 board. It has no external memory bus. That said, the CM3L has an exposed bus for SD cards or eMMC flash, so I suppose, at least in concept, you might be able to have one or more flash memory modules in common across multiple CM3L boards, but that would entail some tricky setup work (it'd be a kind of USB MSD boot arrangement), or a lot software that I don't think exists for the Pi. Shared resource handling gets tricky unless there is a single control device (say, a CM3/CM3L module that "owns" that storage) is used.

While I think your concept is interesting, I don't think it is at all practical the way you appear to be thinking about it. I would suggest that you consider looking up "Beowulf cluster" and then think about inter-node communication using a common carrier board.

Imre
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Re: Expandable baseboard (slot system) for CM3

Sun Jul 16, 2017 7:10 pm

Yes, you are right. Identification of inserted boards needs some kind of (probably) tricky mechanism. We'll see. :)
But I like to use the same sockets on the baseboard (in this case DDR2 SODIMMs, because of the CM3), not to restrict the possible 'card' configuration by using physically different sockets.

According to my pleriminary concept, a system must contain at least one CM3, which would supervise the whole system. Plus one or more CM3s (i.g. in a cluster configuration, as you suggested, where the links between them set up by the underlaying baseboard).
Using dedicated memory mudules would not be necessary. Otherwise it would not be used for expanding the internal memory of CM3, but rather can be a good place to storing shared data for inter-communication between different 'cards'.
And the flavour of the concept would be the use of custom (probably FPGA based) expansion, accelerator modules.

The basis of the development would be the CM3 with its Linux distribution (including its gcc c compiler) for not to start everything from zero. ;)
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Mon Jul 17, 2017 6:46 pm

I've startet designing my own baseboard following such an 'expansion' idea.
What I did is quite simple: 1.8V socket for the CM3 and a 2.5V socket for the expansion board.
As you know: DDR sockets are available for different voltages. The slot in the module prevents you from misplugging it into socket with incorrect voltage level.

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mikronauts
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Re: Expandable baseboard (slot system) for CM3

Mon Jul 17, 2017 6:58 pm

Imre, I am probably stating the obvious here...

1) You do realise the CM3's pins do not form a "bus" in computer terms?

It would be possible to emulate one, but it would be painfully slow.

2) Multiple CM3's could form a cluster, but you would need to add Ethernet PHY's and an ethernet switch

It would also only help for software written for running on a cluster, it would not speedup a specific CM3 at all.
Imre wrote:Yes, you are right. Identification of inserted boards needs some kind of (probably) tricky mechanism. We'll see. :)
But I like to use the same sockets on the baseboard (in this case DDR2 SODIMMs, because of the CM3), not to restrict the possible 'card' configuration by using physically different sockets.

According to my pleriminary concept, a system must contain at least one CM3, which would supervise the whole system. Plus one or more CM3s (i.g. in a cluster configuration, as you suggested, where the links between them set up by the underlaying baseboard).
Using dedicated memory mudules would not be necessary. Otherwise it would not be used for expanding the internal memory of CM3, but rather can be a good place to storing shared data for inter-communication between different 'cards'.
And the flavour of the concept would be the use of custom (probably FPGA based) expansion, accelerator modules.

The basis of the development would be the CM3 with its Linux distribution (including its gcc c compiler) for not to start everything from zero. ;)
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

Imre
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Re: Expandable baseboard (slot system) for CM3

Mon Jul 17, 2017 10:54 pm

Do you have any public information about your project?
aBUGSworstnightmare wrote:I've startet designing my own baseboard following such an 'expansion' idea.
What I did is quite simple: 1.8V socket for the CM3 and a 2.5V socket for the expansion board.
As you know: DDR sockets are available for different voltages. The slot in the module prevents you from misplugging it into socket with incorrect voltage level.
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

Imre
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Re: Expandable baseboard (slot system) for CM3

Mon Jul 17, 2017 11:19 pm

Hi mikronauts,
mikronauts wrote:Imre, I am probably stating the obvious here...

1) You do realise the CM3's pins do not form a "bus" in computer terms?

It would be possible to emulate one, but it would be painfully slow.
I did. My 'secret weapon' would be reverse engineering of the not publicly documented SMI.
If I fail (which is very likely :) ), USB would be my second try.
Then SPI, or UART. While these are point-to-point connections, one or more FPGAs on the baseboard would realize the 'interconnection logic'.
mikronauts wrote:2) Multiple CM3's could form a cluster, but you would need to add Ethernet PHY's and an ethernet switch

It would also only help for software written for running on a cluster, it would not speedup a specific CM3 at all.
I am trying to avoid Ethernet Phy's implementation, but as a fallback solution it is on my list. :)
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Fri Jul 21, 2017 5:30 am

Project is only making slow progress due to time limitations. So sorry, there is nothing to share atm.

Imre
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Re: Expandable baseboard (slot system) for CM3

Mon Jul 24, 2017 7:49 am

Not even an idea? ;)
I am currently thinking what kind of functionalities should be implemented on the expansion boards (cards/modules).
I've made some research on the internet yet to gather some inspirations, but still nothing impressive I could find.
But I don't give it up. :)
aBUGSworstnightmare wrote:Project is only making slow progress due to time limitations. So sorry, there is nothing to share atm.
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Tue Feb 27, 2018 3:44 pm

Imre wrote: I found this:

This is definitely not a board, what I would like to design, but at least, it exists. :)

By my understanding, it is 'nothing more' than integrating CMs and Ethernet switch on one PCB.
But in the other hand, still interesting.

What are your opinions?
Sorry, but how is this related to Raspberry Compute Module?
And ... why do you want to design a board that exists already? Still fishing for other peoples ideas due to the lack of own ones?
BTW: I've designed my own baseboard already; need to finish another board first and then both designs will be send to PCB manufacturer (because shipping costs are expensive)

Imre
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Re: Expandable baseboard (slot system) for CM3

Tue Feb 27, 2018 10:34 pm

Why was my last post completely removed from this topic? It was not (could not be) an advertisment!
I found this:

https://forum.pine64.org/showthread.php?tid=5461

This is definitely not a board, what I would like to design, but at least, it exists. :)

By my understanding, it is 'nothing more' than integrating CMs and Ethernet switch on one PCB.
But in the other hand, still interesting.

What are your opinions?
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

Imre
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Re: Expandable baseboard (slot system) for CM3

Tue Feb 27, 2018 10:51 pm

aBUGSworstnightmare wrote:
Tue Feb 27, 2018 3:44 pm
Imre wrote: I found this:

This is definitely not a board, what I would like to design, but at least, it exists. :)

By my understanding, it is 'nothing more' than integrating CMs and Ethernet switch on one PCB.
But in the other hand, still interesting.

What are your opinions?
Sorry, but how is this related to Raspberry Compute Module?
And ... why do you want to design a board that exists already? Still fishing for other peoples ideas due to the lack of own ones?
BTW: I've designed my own baseboard already; need to finish another board first and then both designs will be send to PCB manufacturer (because shipping costs are expensive)
I don't want to design a board like that one. Why do you think this?
Please read my opening post!

I am just curious why could not find anything (at least) similar to that one. While I offen read posts about ideas of raspberry 'supercomputers', clusters, etc., still nothing real project I could find.

So, this topic is more or less about discussion of these ideas. I don't want to steal anyone's concept.

Otherwise, I don't understand your attitude. There is no offense from my side.
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

fruitoftheloom
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Re: Expandable baseboard (slot system) for CM3

Wed Feb 28, 2018 10:04 am

Imre wrote:
Tue Feb 27, 2018 10:51 pm
aBUGSworstnightmare wrote:
Tue Feb 27, 2018 3:44 pm
Imre wrote: I found this:

This is definitely not a board, what I would like to design, but at least, it exists. :)

By my understanding, it is 'nothing more' than integrating CMs and Ethernet switch on one PCB.
But in the other hand, still interesting.

What are your opinions?
Sorry, but how is this related to Raspberry Compute Module?
And ... why do you want to design a board that exists already? Still fishing for other peoples ideas due to the lack of own ones?
BTW: I've designed my own baseboard already; need to finish another board first and then both designs will be send to PCB manufacturer (because shipping costs are expensive)
I don't want to design a board like that one. Why do you think this?
Please read my opening post!

I am just curious why could not find anything (at least) similar to that one. While I offen read posts about ideas of raspberry 'supercomputers', clusters, etc., still nothing real project I could find.

So, this topic is more or less about discussion of these ideas. I don't want to steal anyone's concept.

Otherwise, I don't understand your attitude. There is no offense from my side.

"Distributed Computing" or Cluster is only useful for running software which can take advantage of this setup.

If you use CMs you would only have Serial Connections, if you do not want to add USB Ethernet, which is slow.

The Dramble is a good example of not using CMs:

http://www.pidramble.com


Regards CMs there is this post:

viewtopic.php?t=144595
Retired disgracefully.....

Imre
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Re: Expandable baseboard (slot system) for CM3

Tue Mar 20, 2018 9:52 pm

It would not be a typical distributed system, rather a heterogeneous computing, with a common (and only one) OS running on it.

To be honest, I don't know it is possible or not. We'll see.

I think it's time to play a little bit with my Pi3B and FPGA boards together. :)
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Mon Mar 26, 2018 5:44 am

By the way: Here is my interpretation of an 'expandable base board'. Send it to the board house today and will update here in the forum when PCBs are back (and hopefully working).
top.png
LVDS4CM3L
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aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Wed Apr 04, 2018 5:25 am

PCBs are here. Tested the slot footprints to check if/how everything will fit together. Need to assemble some and test if they are working.
IMG_0464.jpg
LVDS4CM3L - alignment of the slots
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IMG_0465.jpg
LVDS4CM3L - Compute Module goes into the upper slot
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Imre
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Re: Expandable baseboard (slot system) for CM3

Sun Apr 22, 2018 8:08 pm

Very nice! How can you insert an expansion card if CM3 slot is populated? Are there enough space?
And what is the main goal of this board?
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Mon Apr 23, 2018 6:44 am

Imre wrote: Very nice! How can you insert an expansion card if CM3 slot is populated? Are there enough space?
And what is the main goal of this board?
simply by removing the CM3.
One goal is to see if it can be done that way,if the design is o.k. for DSI and CSI signals and I2S.
Main goal for me is having single- or dual-channel LVDS (with both typical mappings) from a single board - which nearly needs no extra wiring.

Imre
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Re: Expandable baseboard (slot system) for CM3

Mon Apr 23, 2018 10:57 pm

I meant, that can you have both the CM3 and the expansion card installed at the same time? As I see, the inner socket is taller than the other. Is this displacment enough for it?
'Good luck, Mr. Gorsky!' - Neil Armstrong, July 21, 1969, Moon

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Tue Apr 24, 2018 2:22 pm

Yes, both of them can be mounted (for sure).
CM3 slot is higher; basically that's how SO-DIMMs on some mainboards are arranged

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Mon Sep 03, 2018 7:01 pm

Hi,
Just wanted to add some info (as this thread got quite some hits):
My expandable baseboard for CM3L is working. First two expansion board PCBs were send to board house already. Will report back one they are back (& working)
IMG_0643.JPG
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IMG_0642.JPG
IMG_0642.JPG (116.93 KiB) Viewed 7128 times

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Sun Oct 28, 2018 6:33 pm

duplicate post due to website issues
Last edited by aBUGSworstnightmare on Mon Oct 29, 2018 10:40 am, edited 1 time in total.

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Sun Oct 28, 2018 6:33 pm

Tests with my LVDS4CM3L 'expandable baseboard' are ongoing.
Successfully tested the DSI+CSI (for second camera interface) and the dual-channel LVDS expansion board
IMG_0681.jpg
Dual-channel LVDS expansion board
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IMG_0679.jpg
DSI + CSI expansion board
IMG_0679.jpg (107.17 KiB) Viewed 6740 times
Last edited by aBUGSworstnightmare on Mon Oct 29, 2018 10:40 am, edited 1 time in total.

aBUGSworstnightmare
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Re: Expandable baseboard (slot system) for CM3

Sun Oct 28, 2018 6:36 pm

tested 18.5in Full-HD display on LVDS expansion board:
IMG_0685.JPG
IMG_0685.JPG (137.76 KiB) Viewed 6671 times

John Westlake
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Re: Expandable baseboard (slot system) for CM3

Wed Oct 31, 2018 9:39 pm

Very nice work :) Are you running two independent displays (two frame buffers) on a single CM3? - if so how are they interfaced?

Again, nice to see such professional design work :)

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