manis404
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Re: DEFINITE Raspi DSi screen list

Fri Jan 20, 2012 11:27 pm

I am trying to build a list of screens that we could hook up on the DSI interface.

Every thread I have seen, people want to do things via HDMI etc which I believe is not 100% appropriate for portable application of the RasPi.

So, if anyone knows a DSI (cheap) DSI screen that could interface with the board, please let us know in this thread.

Regards,

M.

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johnbeetem
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Re: DEFINITE Raspi DSi screen list

Fri Jan 20, 2012 11:58 pm

There are some possible DSI screens listed at the RasPi wiki: http://elinux.org/Rpi_Screens#.....LCD_panels

If anyone finds others screens, updating the wiki would be very helpful.

JRC6502
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Re: DEFINITE Raspi DSi screen list

Fri Feb 03, 2012 4:21 pm

Just found this thread, any updates? The wiki is filled with Maybes and "AFAIK"s and "Probably"s. Are there ANY displays in the world that definitely use DSI? It's an incredibly hard term to Google.

jamesh
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Re: DEFINITE Raspi DSi screen list

Fri Feb 03, 2012 4:25 pm

Yes, there are quite a few displays that use DSI.

But just because it uses DSI doesn't mean it will work without driver mods on a Raspi. They all tend to be a little different so each display needs it's own tweaks to the driver. Some work needs to be done on the GPU to allow these tweaks to be done from Linux space rather than having to recompile the driver for each new DSI display.
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Motley
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Re: DEFINITE Raspi DSi screen list

Fri Feb 03, 2012 4:36 pm

All the major panel manufacturers support MIPI DSI. Have a look at http://www.trulydisplays.com/t.....index.html for instance.

WereCatf
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Re: DEFINITE Raspi DSi screen list

Fri Feb 03, 2012 6:07 pm

Just out of the blue: where would one buy these sort of things? Ordering directly from the manufacturers usually requires buying in bulk, ie. atleast 1000 pieces, and while there are some available on eBay not everyone lives in the US. In other words, a place where one can more-or-less internationally order some DSI screen would be plenty nice to add in the wiki.

BertM
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Re: DEFINITE Raspi DSi screen list

Wed Feb 08, 2012 4:17 pm

The screen of the iPhone 4G seems to support MIPI DSI, as long as you provide it with the appropriate voltages to operate. It is available on eBay starting from around 15 USD.

I am buying one and will try to make it work as soon as I have my RPi, but it may be quite a lot of work as their are fine pitched electronics and binary drivers involved.

korgak
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Re: DEFINITE Raspi DSi screen list

Tue Feb 28, 2012 8:57 pm

well the company i work for is a large manufacturor for lcd modules and most projects tend to be mipi dsi these days.

actually all new projects are mipi at themoment. so i think it would be fun to hook one up eventually to the raspberry pi.

does anyone know which mode it will support?(videomode or commandmode)?

how many datalanes? at what speed per lane?

BertM
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 12:19 am

There are two datalanes exposed to the DSI connector.

612WharfAvenue
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 12:24 pm

I think in all the searching for displays one thing is consistently overlooked:  connectors.

I was poking around in a few of the screen threads the other day and noticed that even when there are cheap displays that use DSI (like the iphone screens), they seem to have this socket-type two-row connector to them.

A hurdle that'll need to be overcome is finding something to translate that (with the appropriate pinout) to the flat ribbon connector the Pi takes.   I can't speak for everyone but I know I can't solder stuff that small.   Does anyone have any ideas for where to even begin to look for stuff like that?   Seems unlikely to exist off the shelf.

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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 12:30 pm

Actually there are two things people overlook - the connector, and the driver. Since the driver is on the GPU, the public cannot write them. Needs to be done by the Foundation or someone at Broadcom who  a) Has access to the compiler and linkers b) Knows what they are doing c) Has some spare time. All are possible, but not necessarily right now.
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manis404
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 12:30 pm

The problems with connectors can be solved by just making a breakout board which physically rearranges the individual pins of each side. No big deal, really. The most significant step is to actually find displays that accept DSI signals.

manis404
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 12:33 pm

Of course, making the actual driver takes precedence over finding displays. It would be useless to get displays if we can't even make the raspi TALK through the dsi interface.

BertM
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 12:41 pm

Yes, such an interconnect is a hurdle to overcome. I am quite sure however that someone with moderate soldering skills should be able to build one, provided he has the right connector and professionally made PCB. Keep in mind that such a board would have to provide the correct voltage levels as well.
The driver however might be much more of a problem.

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MattPurland
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 3:38 pm

Hmmm, this panel looks like a nice choice for my project

http://www.trulydisplays.com/t.....20Spec.pdf

JamesH said:


Actually there are two things people overlook – the connector, and the driver. Since the driver is on the GPU, the public cannot write them. Needs to be done by the Foundation or someone at Broadcom who  a) Has access to the compiler and linkers b) Knows what they are doing c) Has some spare time. All are possible, but not necessarily right now.


This is a shame really, a lot of projects will require these types of panels, mostly due to the need of running from a battery pack. But as previously mentioned this isn't the intention of the foundation or part of it's plans. Still, doesn't stop me from wanting it

JamesH: just curious, would a driver need to be written on a per panel basis? The vast range of panels could make this very difficult

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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 5:30 pm

Given the wide variety of ways the data to the display can be sent, and various other hardware configurations its usually a case of writing a new driver for each display, or at the very least taking an existing driver and modifying it.

Its not quite the plug-n-play you get with SVGA displays for example.

612WharfAvenue
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 6:14 pm

~Neil~ said:


Given the wide variety of ways the data to the display can be sent, and various other hardware configurations its usually a case of writing a new driver for each display, or at the very least taking an existing driver and modifying it.

Its not quite the plug-n-play you get with SVGA displays for example.



Care to elaborate?   There seems to be quite the dearth of (openly available)information on the workings of DSI.

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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 6:35 pm

Well, just grab some datasheets of DSI displays and compare the data formats.  Can be many things, such as many bits per colour, how the bits are sent over the DSI lanes, H and V sync modes, front and back porch widths, how many data lanes, maximum clock frequency, drive strength, termination, etc.  Any one of those would be enough to make one driver incompatible with another display.

rmm200
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 6:38 pm

Well given what was said earlier about the DSI lines being controlled by the GPU, and that only Broadcom can write drivers for it - it sounds like DSI is a dead issue.

BertM
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Re: DEFINITE Raspi DSi screen list

Mon Apr 23, 2012 6:50 pm

The parameters you name are very simple ones - a proper driver does not make assumptions on that (imagine what would happen if a DVI/VGA driver would do the same..) They are effictively just display modes and that has little to do with the device driver.

It would be problematic if every display had a different command set, but it seems like most of that is standardized, so it should be possible to write a more-or-less generic driver (just like any other display driver).

There is some information on DSI available, I happened to stumble upon a working draft of the MIPI DSI specification from 2008 (grab it while it's hot).

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Mike Lake
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Re: DEFINITE Raspi DSi screen list

Sat May 05, 2012 6:30 am

Replacement Nintendo DSI screens are readily available, for example from Amazon: http://tinyurl.com/c52h4r3.

I got one and I have shown it on top of a PiHouse in the bottom row of photos on http://www.thepishop.org/cases.htm.

However, we will have to wait until someone produces a suitable driver.
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Re: DEFINITE Raspi DSi screen list

Sat May 05, 2012 6:43 am

The "Nintendo DSi" http://en.wikipedia.org/wiki/N.....ntendo_DSi has small LCD display panels, but do they actually use the MIPI DSI protocol? http://en.wikipedia.org/wiki/D....._Interface

Maybe or maybe not, I don't know. Just wanted to point out I think there are two completely different "DSI" abbreviations possibly being confused here.

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Re: DEFINITE Raspi DSi screen list

Sat May 05, 2012 6:58 am

The drivers do not have to be written for the GPU in future, we have an abstraction that allows the drivers be written on the ARM.

But for the moment it is not yet ported across to the R-Pi codebase.  Plus there is no display available, as soon as Gert has got a display wired up (he's been trying that recently) then I'm sure someone (probably Dom) will port it across.
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Mike Lake
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Re: DEFINITE Raspi DSi screen list

Sat May 05, 2012 3:00 pm

gsh

You seem to know what you are talking about - which is nice <g>

Are the Nintendo DSI displays really DSI displays?
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Re: DEFINITE Raspi DSi screen list

Sat May 05, 2012 4:09 pm

Mike Lake said:


Are the Nintendo DSI displays really DSI displays?


No, it is a bespoke part - you can't even get a datasheet for them. (I was looking round recently when I had to repair my son's Nintendo DS (The DS stands for Developers' system or Dual Screen. The 'i' stand for camera ).

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