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IMX6DL: How to do LCD calibration ?

Question asked by robin singh on Aug 26, 2016
Latest reply on Dec 28, 2016 by vikash patil

Hi All


The red colour on my LCD is little off, it does not exactly looks like perfect red. So i want to calibrate this LCD. And i am looking for the suggestion to do that: 


here is gamma correction steps, i already tried and did not get the good result 

Gamma correction on i.MX6 

ipu-examples release notes - v0.1 


ipu-examples/framebuffer_ex1.c at master · rogeriorps/ipu-examples · GitHub 

Tried above gamma correction sample code but LCD calibration  become more bad.



here is my  platform and  setting for LVDS interface :[ Android 4.4  kernel 3.10 ]

LCD panel uses (HX8282 -Source driver / HX8696 -Gate Driver)    ---SPI interface is not out from the Panel for control so i can not set the panel registers. 


static struct fb_videomode lcdif_modedb[] = {                                  

/* lcd 1024x600 @ 60 Hz , pixel clk @ 66MHz */
"HiMAX-WSVGA", 60, 1024, 600, 25000 , 155, 160, 8, 23, 4, 4,


===( DTS file ) ===========:

mxcfb1: fb@0 {
compatible = "fsl,mxc_sdc_fb";
disp_dev = "ldb";
interface_pix_fmt = "RGB24";
default_bpp = <24>;/*<24>;*/
int_clk = <0>;
late_init = <0>;
status = "okay";


Questions : 

1) I used the ipu example code for gamma correction, where Gout array is :

int gout[16] = {0,2,4,8,16,32,64,96,128,160,192,224,255,255,255,255};  this setting do not have any impact on my LCD color, is there any other gout value for my processor imx6dl , which i need to use or How will i calculate these value , any suggestion ?


2) Reference manual section: Gamma correction says" Required gamma correction slope for a specific panel/display should be provided by the display manufacturer "  , can you point me,   what will be  the value i  will be suing  from gamma slope in the sample code ? 


3) Regarding Data format,    My LCD support RGB stripe(LCD document does not provide good details about this), And "RGB24" is working for me with reasonable  result.  Android HAL is using HAL_PIXEL_FORMAT_RGB_565 . is there anything i need to look from this perspective, In terms of IPU Color space conversion ? 


4) Any other pointer or reference for LCD panel calibration ?  



Robin Singh