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G120 TFT pixel clock question


#1

Hello,

I have a question about the LCD controller inside of the G120, I know the used microcontroller is the LPC1788 of NXP.

I have an 5.0" TFT 800x480 display and like to connect this to the G120, but now I see in the example code of the 7" TFT screen that the pixel clock is configured to 25Mhz, this looks to be slow?

In my datasheet of is the minimal clock 27,32 Mhz, typical 30.06Mhz and max 33.41Mhz, can the G120 give faster clock?

I use the Fez Cobra with EMX module, with the same display and slow then 24Mhz clock gives a very disturb picture.

Kind regards


#2

We use a bit slower clock so the system can keep up. In most cases, you will not notice any flickering.


#3

Hey Gus,

Thanks for the reply and you anwser.

I will give it a try, but the pixel clock can be set higher then 25Mhz?


#4

It may be possible to get a clock higher than 25 MHz but it depends on if the pixel clock divider can provide a specific frequency. If, say, the LCD clock is able to generate 100 MHz, if you use a divider of 3 you can only achieve 33 MHz. So if you set the clock to maybe 30 MHz, only the next divider will work so, it would be 25 MHz. You would need to scope the clock pin to determine the actual value based on the input value.