Polarity of Data Enable (DE) signal from DCU

[valterm]

Is there a way to configure the polarity of DE signal for external displays?

In the DCU documentation I found the DCUx_SYNPOL register (55.5.10 in my version of the reference manual) that contains bits to swap polarity of HSYNC, VSYNC, CLK and even data bits, but no way to change the polarity of DE output signal.

There is the INV_PDI_DE bit, but can be used only for input signal.

Is there a way to configure the bahaviour of DE or we should assume that it can only be active high?

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[naoumgitnik]

Dear Valter,

Sorry for delay...

Are you asking about the DE_POL field in the Extended Configuration Register (VIU3_EXT_CONFIG), please?

(In addition, it can be also searched and found, using the 'Search' window in the upper right corner of the web page, that this aspect is also mentioned in the code excerpt in the Re: Vybird, RGB888 input, RGB888 output, no quality lost??? thread.)

Regards, Naoum Gitnik.

[billpringlemeir]

I think that conversation is on the VIU.  This is for video capture.  Valter was asking about the DCU, which is the Vybrid LCD output (non-segmented).  It seems that many LCD modules use DE in-lieu of the VSYNC/HSYNC signalling.  It gives one lower pin count.  The DE will route to the TCON module, so you should be able to invert it with TCON module.  There is an Appnote by Melissa Hunter called Using the Vybrid TCON Module, and chapter 4.3 - Creating an active low data enable signal seems to be what Valter wants; not as easy as a single bit to invert.