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From: Didi on 26 Feb 2010 02:48
On Feb 26, 12:28 am, D Yuniskis <not.going.to...(a)seen.com> wrote:
> ...
> I want to know how "standardized" the signals presented via
> the "flex circuit" tail are.  Aside from differing numbers of
> "color bits", do all panels use the same basic signal sets?

Hi Don,
more or less they do, lately I am witnessing them to also
specify a *minimum* clock frequency. On older TFT displays
one could lower the clock frequency at will until the colours
began to degrade (because of TFT gate leakage), now this
seems to have changed, perhaps they have some PLLs or sort of.
But I am not sure, have not fought any such wars, just
an observation while considering various parts.

> I.e., how reasonable is it to expect a controller to talk
> to a wide variety of panels (assuming the connections can
> be mechanically accommodated) without requiring significant
> hardware (electronics) changes.

Fairly reasonable, if you get a controller, that is. The last
monolithic one on the market was the b69030 by Chips/Intel/Asiliant,
now there are some hybrids by a Taiwanese manufacturer (this
applies if you are looking for VGA and above resolutions).
Some SOC parts do come with a display controller as well
(unfortunately none I like is still really on the market,
the closest was the MPC5121 but one of its errata said
"the SATA interface won't work; workaround: don't use SATA....).
I am eyeing one of their new QORIQ parts now but it seems
to be still far from anything really usable, let's see if
they will make it (I do hope they will).

>
> E.g., controlling CCFLs is different than an LED backlight.
>

Usually backlight is not considered part of the "controller"
interface, the controller has some TTL output to drive it
on/off, I usually use some GPIOs to make up some sort of
DAC to drive the intensity and that's it. If you want to be
able to use both LED and CCFL backlit panels you will have
to design in both power sources somehow (not a huge issue since
CCFL usually need a tiny convertor board anyway, one could
simply change it as needed).

Dimiter

------------------------------------------------------
Dimiter Popoff Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/
From: Spehro Pefhany on 26 Feb 2010 08:20
On Fri, 26 Feb 2010 00:09:20 GMT, the renowned nico(a)puntnl.niks (Nico
Coesel) wrote:

>D Yuniskis <not.going.to.be(a)seen.com> wrote:
>
>>Hi,
>>
>>Most of the things I design don't have traditional
>>displays, so... :<
>>
>>Aside from mechanical differences in connectors
>>(a consequence of the number of "color bits"),
>>can I safely design a generic LCD interface
>>without preselecting the actual display panel?
>
>You cannot. Selecting an affordable panel is a world of pain. Make
>sure you can get the cables as well!

I'm in the middle of trying to find sources for a small QVGA panel,
there seem to be some "almost compatible" COG chips (from Taiwan). The
chips are a bit strange since they don't need to be packaged, they are
shaped like matchsticks. Anyway, several seem to use a common FPC
pinout but even then all the modes may not be available (and the most
tempting modes to omit probably the ones *you* would want- the ones
that are not used for video display).


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff(a)interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
From: linnix on 26 Feb 2010 13:22
On Feb 26, 5:20 am, Spehro Pefhany <speffS...(a)interlogDOTyou.knowwhat>
wrote:
> On Fri, 26 Feb 2010 00:09:20 GMT, the renowned n...(a)puntnl.niks (Nico
>
> Coesel) wrote:
> >D Yuniskis <not.going.to...(a)seen.com> wrote:
>
> >>Hi,
>
> >>Most of the things I design don't have traditional
> >>displays, so...  :<
>
> >>Aside from mechanical differences in connectors
> >>(a consequence of the number of "color bits"),
> >>can I safely design a generic LCD interface
> >>without preselecting the actual display panel?
>
> >You cannot. Selecting an affordable panel is a world of pain. Make
> >sure you can get the cables as well!
>
> I'm in the middle of trying to find sources for a small QVGA panel,
> there seem to be some "almost compatible" COG chips (from Taiwan). The
> chips are a bit strange since they don't need to be packaged, they are
> shaped like matchsticks.

They are designed to be mounted directly on the glass, usually 0.1mm
pitch.

> Anyway, several seem to use a common FPC
> pinout but even then all the modes may not be available (and the most
> tempting modes to omit probably the ones *you* would want- the ones
> that are not used for video display).

LCD does not need hsync and vsync. There is no beam to retrace
anyway.

From: D Yuniskis on 26 Feb 2010 16:16
Hi Dimiter,

Didi wrote:
> On Feb 26, 12:28 am, D Yuniskis <not.going.to...(a)seen.com> wrote:
>> ...
>> I want to know how "standardized" the signals presented via
>> the "flex circuit" tail are. Aside from differing numbers of
>> "color bits", do all panels use the same basic signal sets?
>
> more or less they do, lately I am witnessing them to also
> specify a *minimum* clock frequency. On older TFT displays
> one could lower the clock frequency at will until the colours
> began to degrade (because of TFT gate leakage), now this
> seems to have changed, perhaps they have some PLLs or sort of.

Or, perhaps an onboard buffering just preserving a "classic
interface"?

> But I am not sure, have not fought any such wars, just
> an observation while considering various parts.
>
>> I.e., how reasonable is it to expect a controller to talk
>> to a wide variety of panels (assuming the connections can
>> be mechanically accommodated) without requiring significant
>> hardware (electronics) changes.
>
> Fairly reasonable, if you get a controller, that is. The last
> monolithic one on the market was the b69030 by Chips/Intel/Asiliant,
> now there are some hybrids by a Taiwanese manufacturer (this
> applies if you are looking for VGA and above resolutions).
> Some SOC parts do come with a display controller as well
> (unfortunately none I like is still really on the market,
> the closest was the MPC5121 but one of its errata said
> "the SATA interface won't work; workaround: don't use SATA....).
> I am eyeing one of their new QORIQ parts now but it seems
> to be still far from anything really usable, let's see if
> they will make it (I do hope they will).

I'm just trying to reduce the number of variables in the
design process. I.e., if I can pick a controller and
design around that and *later* pick a display panel, that's
much easier than waiting until *all* of the choices have been
made and then rushing to accommodate all of them in a cohesive
design.

>> E.g., controlling CCFLs is different than an LED backlight.
>
> Usually backlight is not considered part of the "controller"
> interface, the controller has some TTL output to drive it
> on/off, I usually use some GPIOs to make up some sort of
> DAC to drive the intensity and that's it. If you want to be
> able to use both LED and CCFL backlit panels you will have
> to design in both power sources somehow (not a huge issue since
> CCFL usually need a tiny convertor board anyway, one could
> simply change it as needed).

Yes. In my case, I want to put all of the display interface on a
small board (LCD interface, backlight, touchpanel, etc.). So,
if I end up with a panel that has LED backlighting, I need
to have provisions for that on my board. Likewise, if I
aimed for a CCFL backlight, then I would need the hooks to
turn that backlight on, vary it's intensity, detect faults
in the inverter, etc.

I'm just trying to gauge what approach is safest to follow.

--don
From: -vinnie- on 1 Mar 2010 11:51
On Feb 26, 4:16 pm, D Yuniskis <not.going.to...(a)seen.com> wrote:
> Hi Dimiter,
............
> Yes.  In my case, I want to put all of the display interface on a
> small board (LCD interface, backlight, touchpanel, etc.).  So,
> if I end up with a panel that has LED backlighting, I need
> to have provisions for that on my board.  Likewise, if I
> aimed for a CCFL backlight, then I would need the hooks to
> turn that backlight on, vary it's intensity, detect faults
> in the inverter, etc.
>
> I'm just trying to gauge what approach is safest to follow.
>
> --don-

yes, your approach is good. Stay away from COG if you are looking at
minimal changes from supplier to supplier, since everyone seems to
pick a different COG controller.

The 16 or 24 bit interface is fairly standard (although the connectors
vary from supplier to supplier.) Many of these also include a I2C
channel to manage setup information.

Here's a development kit from Renesas that uses a "standard" TFT LCD
interface to talk to many different panels using an intermediate
connector board based on the LCD supplier.
http://america.renesas.com/products/mpumcu/h8/h8_lcd/h8_lcd_landing.jsp
http://america.renesas.com/media/products/mpumcu/h8/h8_lcd/child_folder/Direct_Drive_LCD_Demo_Application_Note.pdf

--Vinnie

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