This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AM3358: LCDC timing edge between HSYNC and VSYNC

Part Number: AM3358


Sorry if this is a basic question but a customer is (in Linux tweaking device tree file) trying to configure the LCD controller on the AM335x to output in raster mode active TFT with active low Hsync and Vsync signals.  Basically the below picture from p. 1952 of the TRM (AM335x_TRM_spruh73q).pdf .  But the HSYNC signal is falling low almost 7 cycles before the Vsync and they need to be  ~1 cycle.  The "porch" settings seem to help with data getting driven but not the timing edge between HSYNC and VSYNC.

How do we control the LCDC timing edge between HSYNC and VSYNC?

  • Aligning the edges of the VSYNC and HSYC, even within 1 clock cycle, is  not a feature supported by the LCDC. 

    A possible workaround is to invert the HSYNC so that it appears to the LCD display that the edges are aligned (no delta). However, this will result in a HSYNC "pulse" that is the entire length of the horizontal line, less the HSYNC width, which may also be an issue for the LCD display. 

    --Paul