NHD-7.0-800480EF-ATXV#-CTP dull display

lakshminarayanan

• November 19, 2014 07:46

Hi ,

Good day, we are using NHD-7.0-800480EF-ATXV#-CTP display in our system. the display is working. but the display looks very dull. we have changed the display brightness for the full range. but still the display looks dull.  we don't know where to check and what to check.

1) we are doubting for contrast issue. if it is contrast issue how to tune it. In the LCD display interface we have no relevant signals for that

Please help us to fix it

Regards
Lakshminarayanan

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  Michael_L

  • November 20, 2014 07:46

  I have not seen this before, however, there is no contrast setting adjustment available.  I doubt it is the display, but do you have another to try?  Try changing some of your display signal timings (i.e. CLK, HSYNC, VSYNC) and see if it changes anything for you in terms of this "dullness" you are seeing.  Also, what voltage are you supplying the display with?  What are the voltage levels of your signals?  When you say you changed the brightness to the full range, are you referring to the backlight?  Have you checked the backlight current to make sure it is within spec?

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  lakshminarayanan

  • November 24, 2014 07:46

  Hi Michael,
  
  Thanks for the reply.
  1) We have tried with other display. still we get the same problem
  2) the HSYNC, VSYNC timings are ok. when we changed them the display is rolling.
  3) We are supplying 17V to the display (back light).
  (the supply is driven from a boost converter, in that converter we do not set any output voltage. we set only over voltage protection range(our case 18V). but the voltage output  is built to drive enough the LCD backlight diodes. In our case the output voltage is built upto 17V. Boost converter part no is: TPS61199PWP
  4) the signals are (RGB, control) are above 3V
  5) for brightness checking, we changed the back light PWM
  
  We are trying also for gamma correction, hue correction using software. still we have the problem
  
  Can you diagnose what kind of problem can make the display to behave like this. Since we are new to display, we are not sure where to check.
  
  Please help us
  
  Regards
  Lakshminarayanan N

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  Michael_L

  • November 25, 2014 07:46

  How are your connections to the display?  Do you have a schematic you can share?

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  lakshminarayanan

  • November 25, 2014 09:46

  Hi Michael,
  
  Thanks for your support. we have fixed the problem.
  
  The problem is the microprocessor was configured for18 bit display interface. but the display is 24 bit interface. the MSB of RGB (R6, R7, G6,G7,B6,B7) are driven as "1" by the microprocessor. thats why the display looks saturated. right now we isolated the those 6 bits R6, R7, G6,G7,B6,B7 from driving the the 24 bit display. after this change the display works good. but some what dull. because R6, R7, G6,G7,B6,B7 are "0" now. we could not reach the full brightness.
  
  We have requested our software team to configure the microprocessor display interface to 24 bit. once they have configured, we can use those 6 bits and get the full brightness of the display.
  
  Thanks for your support Michael.  good day
  
  Regards

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  Michael_L

  • November 26, 2014 09:46

  You're welcome!  Thank you for sharing your issue & solution!

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