universal display driver: how to mirror/unmirror a display?

[marcelgsteiger]

The universal driver docs say that the stanzas :0 :1 :2 :3 contain the rotation code at the first position in the line.
Can anybody explain this code? Can this code be used to mirror the display as well? My display hardware works, but everything is mirrored horizontally (see photo). I'm using the descriptor file tasmota/displaydesc/ST7789_172x320_Waveshare_esp32c6_lcd_1_47.ini .

This is a board named ESP32C6 Touch LCD 1.47, I'm currently preparing a autoconf file for this board (including touch), but I am stuck trying to get rid of this mirror effect.

Any help would much be appreciated.

[sfromis]

Not sure where you got "at the first position in the line", the rotation code is the last entry in each of the 4 lines covering the 4 possible rotations. The mentioned display descriptor has:

:0,C0,22,00,00
:1,A0,00,22,01
:2,00,22,00,02
:3,60,00,22,03

Look for "rotation pseudo opcode" in https://tasmota.github.io/docs/Universal-Display-Driver/#descriptor-file

Last digit is 0 for no conversion, 1 swap and flip x, 2 flip x/y, 3 swap and flip y
The mirroring has to do with flip. You can try adjusting, and see how it works.
Which one covers your current rotation depends on what DisplayRotate shows.
Better get all 4 right when you've started fixing.

[marcelgsteiger]

I've tried that, without success. According to the doc, the fourth parameter is the pseudo-opcode for aligning the rotation of the touch controller relative to the display, right? For manipulating the display itself, I suspect that I have to adapt the first parameter, but I can't find the meaning of the bits.

In the ST7789 datasheet, I see that the MADCTL opcode could be responsible for this (0x36h) by setting the MX bit in the MADCTR, but when I try to adapt this opcode in the :I section nothing happens. I'm unsure on how these initialization bytes are processed in the driver.

[sfromis]

For ST7789, MADCTL should indeed be relevant, and AFAICT, this is directly the first value in the 4 rotation lines, with these bits:

7  MY  Row Address Order    (0 = Top-to-Bottom, 1 = Bottom-to-Top / Mirror Y)
6  MX  Column Address Order (0 = Left-to-Right, 1 = Right-to-Left / Mirror X)
5  MV  Row/Column Exchange  (0 = Normal, 1 = Reverse/Swap X and Y for Landscape)

[marcelgsteiger]

Thanks a lot, this solves the problem. This is the preliminary display.ini for this board (with the touch section still missing):

:H,ST7789,172,320,16,SPI,1,*,*,*,*,*,*,*,40
:S,2,1,3,0,80,30
:B,80,0
:I
01,A0
11,A0
3A,81,55
36,81,00
21,80
13,80
29,A0
:o,28
:O,29
:A,2A,2B,2C
:R,36
:0,88,22,00,01
:1,E8,00,22,02
:2,48,22,00,03
:3,28,00,22,00
:i,21,20
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