Home > LCD, microcontrollers, PIC32 > Using Tearing Line Output from Nokia LCD

Using Tearing Line Output from Nokia LCD


Nokia LCDs mentioned in this blog has tearing line output feature. It can be used to synchronize MCU->LCD writes with LCD display memory scan pointer.
What for? To prevent showing partially content we want to write to LCD’s display RAM.

Problems :
A) your MCU should be fast enough to stream whole framebuffer to LCD within TE (Tearing Effect line output) pulse -> then, LCD read pointer won’t start scanning the frame before whole MCU->LCD transfer ends.
OR:
B) your MCU should be fast enough to stream whole framebuffer to LCD between n and n+2 TE pulses -> then LCD read pointer starts before write to LCD display memory occurs and write pointer will be always behind read pointer of LCD’s memory controller.

If your MCU isn’t fast enough to meet these requirements, tearing would always appear…

TE pulse width is given by LCD’s frame refresh rate (default ~60Hz).
At 60Hz frame scan time is about 16ms. Full frame is 320x240x3 bytes = 230400 bytes. To be able to write full framebuffer during two frame scan time (option B) your MCU should have data computation & throughput speed ~7 MB/s…
Well, it is impressive in the world of cheap and easy MCUs, even PIC32s đŸ™‚

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Categories: LCD, microcontrollers, PIC32 Tags: , , , , , ,
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