orta
Posts: 7
Joined: Wed Jun 03, 2015 11:14 pm

Can CM3 be used as CM3L by removing the EMMC

Tue May 08, 2018 3:38 pm

Hi , I just bought a CM3 and I found that the emmc is not enough for raspibian .
So I hope to change my CM3 to CM3L, by removing the emmc chip.

Now I have removed the emmc, and flashed raspibian image to TF card, then insert the card and boot.
But there is no image from hdmi, the pi seems not working?

So I wonder if CM3 with removed emmc can be used as a CM3L?

PhilE
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1767
Joined: Mon Sep 29, 2014 1:07 pm
Location: Cambridge

Re: Can CM3 be used as CM3L by removing the EMMC

Tue May 08, 2018 8:04 pm

The software (firmware and kernel) is not really made aware of the differences between the CM3 and CM3L, so by carefully reading the CM3/CM3L schematic you might be able to see how to turn one into the other, but I can't guarantee that it will work.

fruitoftheloom
Posts: 16907
Joined: Tue Mar 25, 2014 12:40 pm

Re: Can CM3 be used as CM3L by removing the EMMC

Tue May 08, 2018 9:48 pm

orta wrote:
Tue May 08, 2018 3:38 pm
Hi , I just bought a CM3 and I found that the emmc is not enough for raspibian .
So I hope to change my CM3 to CM3L, by removing the emmc chip.

Now I have removed the emmc, and flashed raspibian image to TF card, then insert the card and boot.
But there is no image from hdmi, the pi seems not working?

So I wonder if CM3 with removed emmc can be used as a CM3L?

Why not get a 16GB CM3 ??

https://www.nec-display-solutions.com/p ... ODEL.xhtml
Adieu

orta
Posts: 7
Joined: Wed Jun 03, 2015 11:14 pm

Re: Can CM3 be used as CM3L by removing the EMMC

Wed May 09, 2018 12:40 am

PhilE wrote:
Tue May 08, 2018 8:04 pm
The software (firmware and kernel) is not really made aware of the differences between the CM3 and CM3L, so by carefully reading the CM3/CM3L schematic you might be able to see how to turn one into the other, but I can't guarantee that it will work.
thank you, I read the schametic and short R12 R16 R17 R18 R19 R25 , disconnect R24 , but the pi still can not boot

orta
Posts: 7
Joined: Wed Jun 03, 2015 11:14 pm

Re: Can CM3 be used as CM3L by removing the EMMC

Wed May 09, 2018 12:42 am

fruitoftheloom wrote:
Tue May 08, 2018 9:48 pm
orta wrote:
Tue May 08, 2018 3:38 pm
Hi , I just bought a CM3 and I found that the emmc is not enough for raspibian .
So I hope to change my CM3 to CM3L, by removing the emmc chip.

Now I have removed the emmc, and flashed raspibian image to TF card, then insert the card and boot.
But there is no image from hdmi, the pi seems not working?

So I wonder if CM3 with removed emmc can be used as a CM3L?

Why not get a 16GB CM3 ??

https://www.nec-display-solutions.com/p ... ODEL.xhtml
I think 16GB EMMC is low cost performance . I rather use >=64GB TF card instead of emmc

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1282
Joined: Sat Sep 10, 2011 11:43 am

Re: Can CM3 be used as CM3L by removing the EMMC

Wed May 09, 2018 2:29 pm

You would also have to add 0R links for the signals to be connected through to the edge connector, R16,17,18,19

Gordon
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

PhilE
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1767
Joined: Mon Sep 29, 2014 1:07 pm
Location: Cambridge

Re: Can CM3 be used as CM3L by removing the EMMC

Wed May 09, 2018 2:33 pm

And R12?

John Westlake
Posts: 55
Joined: Thu Nov 09, 2017 4:34 am

Re: Can CM3 be used as CM3L by removing the EMMC

Sat Jul 14, 2018 2:45 am

orta wrote:
Wed May 09, 2018 12:40 am
thank you, I read the schametic and short R12 R16 R17 R18 R19 R25 , disconnect R24 , but the pi still can not boot
To convert a CM3 to CM3Lite*

("Read note about SDX_VREF limitation):-

Move R10 to R9 (0R)
Move R24 to R25 (33R)

Add R9, R12, R16, R17, R18, R19 (0R)

As the onboard eMMC is still connected to the "external' SD Datalines I suggest that its best to put the onboard eMMC memory into Reset state in the belief that the I/O pads of the onboard eMMC will be held Tri-Stated (High Impedance):-

Repostion R13 (0R) so that the onboard eMMC Reset line is held Low (Reset State) - see attached image:-

https://www.dropbox.com/s/2szzzgk2sipyo ... T.bmp?dl=0

I modified a CM3 as above and a quick test shows its seems to work OK = works as a CM3Lite, but be aware that the onboard eMMC is still physically connected to the external eMMC Bus lines (there is no way to isolate the onboard eMMC without removing it). I suggest that SDX_VREF (Pins 4 & 6 on the CM3 SODIMM connector) should be no higher then 1.8V to prevent damage to the onboard eMMC (which is rated for 1.8V operation).

Its really best to remove U7, the onboard eMMC if you have a BGA rework station (If your skilled then a decent Hotair station and underside pre-heater set around 180DegC to 200DegC works OK).

The CM3 / CM3Lite are manufactured using Lead-Free solder and as we all know LF is just horrid to rework with... Only attempt to rework these modules if you have suitable rework tools and optical systems - the above components are tiny...! You WILL require Micro Rework skills and the suitable tools...

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