LCD Controller ST7529 Grayscale?

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#1
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I'm having a bit of a problem getting an ST7529 based graphics LCD module displaying pixels in grayscale. If you've used this controller for grayscale display I'd be mighty happy to hear how you got it to work.

Thanks,

Tom

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Doesn't that adjustment happen uniformly for all pixels by means of an analog voltage? This may be a coincidence but I was evaluating some new backlit color graphics LCD display from Densitron. They use this controller, and now that you mention it all the pixels in the pictures appear to be the same contrast.

I have the datasheet from Sitronix. As near as I can tell you have several choices of format for writing data to the display controller. There is the 1 byte per pixel arrangement, and there is the packed arrangement of 2 bytes for three pixels. Which one are you trying to use?

We never have time to do it right,
but we always have time to do it over

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Thanks for the reply. We are using the 3B3P, 8-bit mode. That's 3 bytes for 3 pixels. We also set the Gray 1 (odd frames) and Gray 2 (even frames) values of 16 bytes each. When we fill the display memory with a value that maps to one of the gray scale values we see much flickering but not a gray scale block.

Tom

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Since I can't see what is going on on your end I'm going to ask a series of questions which may seem stupid to you, but will help me understand what you are doing.

Are you using the 8 bit parallel interface?
Are you using 6800 Mode or 8080 mode?
Did you remember to shift the grayscale values 3 bits to the left?
Are Gray1 and Gray2 just constant values from [0..31] which must be shifted left 3 bits before being written to Display RAM?

Can you read data back from the controller RAM?
Does it match what you wrote?

We never have time to do it right,
but we always have time to do it over

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I am using the 8-bit 8080 mode. The pixel value written to LCD memory is being shifted left 3 bits. The Gray 1 & 2 values are currently set to constants from 0..31. We are able to read what we've written to LCD memory and it does match.

I think I've narrowed the problem down to a Vlcdout that is not well regulated. I'm displaying horizontal bars, each consisting of 16 lines at a different gray scale value. As I increase the horizontal length of the bars in 60-pixel steps I observe Vlcdout change from 22V down to 15V. I'm not achieving good Vlcdout regulation over the range of load on the glass with the current values of oscillator frequency and boost frequency. So far, I can affect the stability of Vlcdout by changing either of these parameters but I have not found the optimum values that result in a stable voltage across the change from all pixels on to all pixels off or even some pixels on and all pixels off.

The Chinese manufacturer of the LCD has not provided the optimum setup values. We are having custom glass designed with chip on flex for the ST7529 and are using this current display in prototypes to get most of the firmware development done while waiting for the custom glass.

For better or worse, the Chinese module we are using has the default values for the boost caps. Perhaps this is the best it gets with their design and I'll have to muck with the cap values. Our choice of off-the-shelf modules based on the ST7529 was somewhat limited when we purchased these.

Tom

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Try the Densitron Modules:
http://www.densitron.com/display...
I'll bet you can score a handful of samples

We never have time to do it right,
but we always have time to do it over

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Hello Tom,

I'm having the same problem with the same driver, I configure VLCD=16.8v, but it get values between 9v and 14.2v, it depends on the PWM gray level and the colors used in the display. What are gray value parameters for?, according to datasheet:
"The ST7529 applies 16-gray level and 2 FRC to achieve 32-gray scale display. Every gray level is in the strength controlled by 31-PWM (5-bit)."
What does it mean?
How do you configure "Gray 1 set" and "gray 2 set" parameters?.
I set first 8 bytes from each parameters to 31, and the other ones to 0, so I can use the display as black and white, I'm not able to use it as gray scale.

Thanks

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I have changed the multiplier configuration from 6X to 7X and now it works OK.

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hi,
i am using lcd with same controller ST7529 with 8-bit 8080 mode 240x128 resolution, i can set VLCDout but i can't write a character on put pixel on.
plz help

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Hi,
where do you get your displays from?
I am looking for a LCD with about 160x128 pixel and grayscale, but I cant find any supplier for grayscale LCDs.
Does someone knows a supplier for greyscale LCDs?