TFT contrast problem
in [Embedded]
|
Prev: Monochrome LCDs
Next: ATA Protocol
From: hapedo on 23 Apr 2008 07:27 Dear colleagues, I'm trying to interface Casio 3,5" TFT display (COM35T3193KTC) to Epson S1D13705 controler and Freescale MC56F8366 DSP. After a day of timing configuring everything seems to be OK but I have one big problem with display contrast and colors - it's not possible to display whole black screen. When I fill screen with white colour It's possible to display only very narrow colour bars (width about 20 pixels, height is unlimited) without colour defects. When bar width is increased contrast is bad and if width is nearly 320 px colors are inverted. I've measured all voltages generated by display (-12V, 12V and others) and it's OK except VDD2 (5,65V and datasheet says 4,8V in timing diagram, not defined in any DC characteristics). I really don't know how to continue in my project. Thank you for any help.
From: Stef on 23 Apr 2008 07:40 In comp.arch.embedded, hapedo <phapal(a)viditech.cz> wrote: > Dear colleagues, > I'm trying to interface Casio 3,5" TFT display (COM35T3193KTC) to Epson > S1D13705 controler and Freescale MC56F8366 DSP. After a day of timing > configuring everything seems to be OK but I have one big problem with How did you configure timing? We did a 13706 using epson's configuration utility and found that will not output the correct value for the pixel clock divider, resulting in pck=clkin. Hand check all output values from that utility if you use something simular. -- Stef (remove caps, dashes and .invalid from e-mail address to reply by mail) Vuiodh qeoh jh wdhf poqufmnv alkhf adsfoj ad? Hjiyu qsdiyupq dff asdf!
From: hapedo on 23 Apr 2008 08:56 >In comp.arch.embedded, >hapedo <phapal(a)viditech.cz> wrote: >> Dear colleagues, >> I'm trying to interface Casio 3,5" TFT display (COM35T3193KTC) to Epson >> S1D13705 controler and Freescale MC56F8366 DSP. After a day of timing >> configuring everything seems to be OK but I have one big problem with > >How did you configure timing? We did a 13706 using epson's configuration >utility and found that will not output the correct value for the pixel >clock divider, resulting in pck=clkin. Hand check all output values from >that utility if you use something simular. > > >-- >Stef (remove caps, dashes and .invalid from e-mail address to reply by mail) > >Vuiodh qeoh jh wdhf poqufmnv alkhf adsfoj ad? Hjiyu qsdiyupq dff asdf! > Thanks for reply. I've used Epson's config utility too. CLKI = 6,25MHz, pixel clock = CLKI, frame rate = 50Hz (512 clocks per line). I've measured all signals by scope and it's ok. I think there is some problem with panel. I have only one panel for my prototype board. Is there some possibility that panel was degraded during firmware developement? Panel is 24 bit and s1d13705 12 bit only - I have R G and B LSBs grounded.
From: suresh shenoy on 23 Apr 2008 09:00 On Apr 23, 7:27 am, "hapedo" <pha...(a)viditech.cz> wrote: > Dear colleagues, > I'm trying to interface Casio 3,5" TFT display (COM35T3193KTC) to Epson > S1D13705 controler and Freescale MC56F8366 DSP. After a day of timing > configuring everything seems to be OK but I have one big problem with > display contrast and colors - it's not possible to display whole black > screen. When I fill screen with white colour It's possible to display only > very narrow colour bars (width about 20 pixels, height is unlimited) > without colour defects. When bar width is increased contrast is bad and if > width is nearly 320 px colors are inverted. I've measured all voltages > generated by display (-12V, 12V and others) and it's OK except VDD2 (5,65V > and datasheet says 4,8V in timing diagram, not defined in any DC > characteristics). I really don't know how to continue in my project. Thank > you for any help. You say you are looking at a narrow color bars but the height is unlimited. So you have about 20 pixels of color and no activity on rest of the panel? Is your memory mapped correctly? I would make sure the configuration is correctly set. I have worked on S1D13A05 and you will have to check the signals on the scope to make sure all the timings are right. The data sheet for that module has timing diagrams and that will help you set up the correct values. The configuration utility was not able to give us precise values. Suresh M. Shenoy
From: hapedo on 23 Apr 2008 09:31
>On Apr 23, 7:27=A0am, "hapedo" <pha...(a)viditech.cz> wrote: >> Dear colleagues, >> I'm trying to interface Casio 3,5" TFT display (COM35T3193KTC) to Epson >> S1D13705 controler and Freescale MC56F8366 DSP. After a day of timing >> configuring everything seems to be OK but I have one big problem with >> display contrast and colors - it's not possible to display whole black >> screen. When I fill screen with white colour It's possible to display only= > >> very narrow colour bars (width about 20 pixels, height is unlimited) >> without colour defects. When bar width is increased contrast is bad and if= > >> width is nearly 320 px colors are inverted. I've measured all voltages >> generated by display (-12V, 12V and others) and it's OK except VDD2 (5,65V= > >> and datasheet says 4,8V in timing diagram, not defined in any DC >> characteristics). I really don't know how to continue in my project. Thank= > >> you for any help. > >You say you are looking at a narrow color bars but the height is >unlimited. So you have about 20 pixels of color and no activity on >rest of the panel? >Is your memory mapped correctly? I would make sure the configuration >is correctly set. I have worked on S1D13A05 and you will have to check >the signals on the scope to make sure all the timings are right. The >data sheet for that module has timing diagrams and that will help you >set up the correct values. The configuration utility was not able to >give us precise values. > >Suresh M. Shenoy > No, panel is mapped correctly - I'm able to draw any pixel i want. The problem is following: If I draw very short horizontal line (i.e. 20px long) the color of the line is correct. But if the line is bigger (100px or more) color starts to change - It's loosing contrast. If the line is more than 200px long color of the whole TFT panel row starts to be inverted. The result is that It's not possible to fill display with black colour because black changes to white. It's possible to draw only very narrow black bars from top to bottom (over all 240 lines), but when width is increasing black changes to grey. I'll will make and upload some photos to my FTP server. |