aBUGSworstnightmare
Posts: 1071
Joined: Tue Jun 30, 2015 1:35 pm

Re: Expandable baseboard (slot system) for CM3

Wed Oct 31, 2018 10:35 pm

John Westlake wrote: 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 :)
yes, I'm doing dual framebuffer beta testing atm (for details please refer here viewtopic.php?f=63&t=216399).

I've designed the board as a 'successor' of my LVDS4PI Single-Channel LVDS addon for standard Raspberry because I needed a full featured dual-channel LVDS interface. So, first one is 'bridged' from HDMi, leaving DPI free. So, why not add a second LVDS to DPI...

John Westlake
Posts: 84
Joined: Thu Nov 09, 2017 4:34 am

Re: Expandable baseboard (slot system) for CM3

Wed Oct 31, 2018 10:58 pm

That's brilliant news that someone is working with the dual framebuffer beta testing - sadly software is well beyond my skills.

Will your board be available for sale? I'm really keen on adding a display panel on the DPI port for the products "Front Panel" interface / user controls and still have HDMI free for the main external UI.

While your board is dual LVDS output (which is nice in itself) - I would learn a lot working with it on how to meet our display requirements - its always easier to start with something that works :)

aBUGSworstnightmare
Posts: 1071
Joined: Tue Jun 30, 2015 1:35 pm

Re: Expandable baseboard (slot system) for CM3

Fri Nov 02, 2018 6:41 am

John Westlake wrote:
Wed Oct 31, 2018 10:58 pm
That's brilliant news that someone is working with the dual framebuffer beta testing - sadly software is well beyond my skills.
The software is all done by jamesh, I'm testing only (on different HW platforms, different display constellations)

John Westlake wrote:
Wed Oct 31, 2018 10:58 pm
Will your board be available for sale? I'm really keen on adding a display panel on the DPI port for the products "Front Panel" interface / user controls and still have HDMI free for the main external UI.
That's a good question!
As I don't know if there is any market for such a board I was thinking of running a Kickstarter campaign to see if it can be funded. As there are so many LVDS modules available to the market - from notebooks, tablets, industrial or automotive grade LCD's, .. - I came to the idea for this board, because it would allow to up-cycle them in a an easy way - without the need for additional hardware (namely A/D-converter boards).

Connecting a display to DPI is not a big deal if you know how to read a LCM module data sheet. Touch is something which requires some careful decisions (if you go with I2C or USB, is there a driver available already, etc). It's also possible to connect some bridge chip to DPI.

There are enough standard Raspberry Pis out there which expose a HDMI interface (requiring an additional A/D-converter in the 'monitor') I decided to have LVDS interface only. DSI and CSI connector (in both cases the 4-lane modules) are available from the expansion socket. I have a PCB for using them with the official display.
IMG_0686.jpg
CSI+DSI expansion PCB
IMG_0686.jpg (53.69 KiB) Viewed 166 times
As the board is designed to be highly hackable one can design his own expansion board in case there are different requirements.
The expansion is simply a SODIMM DDR2 form factor PCB.
John Westlake wrote:
Wed Oct 31, 2018 10:58 pm
While your board is dual LVDS output (which is nice in itself) - I would learn a lot working with it on how to meet our display requirements - its always easier to start with something that works :)
Look at the posts related to 'LVDS4PI' in the forum to get some ideas/hints.
IMG_0677.jpg
offical DSI display, connected via board shown above
IMG_0677.jpg (55.19 KiB) Viewed 162 times

aBUGSworstnightmare
Posts: 1071
Joined: Tue Jun 30, 2015 1:35 pm

Re: Expandable baseboard (slot system) for CM3

Fri Nov 09, 2018 4:25 am

Testing the board with two 10.1in WXGA displays
https://youtu.be/HFYg63suLoM

Display on the left is connected to the expansion slot (secondary LVDS interface), the right one is connected to HDMI (primary LVDS). Total resolution of the OS desktop is 2560x800 pixels for this setup.

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