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LCD Interrupts: What is freescales notion of VSync and Front Porch interrupts?

Question asked by Martin Kjeldsen on May 26, 2014
Latest reply on Jun 18, 2014 by Martin Kjeldsen



I'm having a bit of trouble determining the proper configuration on the Kinetis platform for some of the common LCD interrupts. Usually, i'd be able to configure registers to trigger interrupts for something like the following:


  • Start of vertical synchronization
  • Start of back porch
  • Start of front porch.


In the K70-sub family (MK70FN1M0VMJ12) reference manual, starting at page 2202, we can handle LCD interrupts using the LCDC_LICR, LCDC_LIER and LCDC_LISR registers. The manual names concepts like Begin Of Frame (BOF), End of Frame (EOF), on load of last/first data of frame from memory, on outout of last/first data to LCD panel - And is seems that a combination of these settings should comprise the notion of Vsync and front/back porch.


Currently, my idea of a Front Porch interrupt is to set interrupt flag on output of last data of frame to LCD panel. And for VSync to set interrupt flag on load of first data of frame from memory - For both these settings, Begin Of Frame is configured in the LICR and LIER registers. I'm not interested in EOF, i think, unless EOF in some way relates to Front Porch, but in this case it seems like on output of last data of frame to LCD panel fits more precisely. 


I'm seeing some glitching because my framebuffers seem like they're being swapped while i'm drawing to the display. I'd like the swap to happen before Back Porch begins, but something tells me the above interpretations aren't correct.


Thanks in advance!