I'm trying to get a HX8369A based lcd to display 18-bit parallel RGB. I've got it working but the colors look terrible. A lot of pixels just go to green like the color data is incorrect. I've tried a variety of timings but it doesn't help.
Does this seem like a timing issue? Is the software giving bad color data? Could my LCD be expecting color data in a slightly different format?
I'm using an IMX6S based RIoTboard which only has DISP_DAT0 - DISP0_DAT17 accessible on the header so I can't use 24 bits. Kernel 3.0.35, Android 4.3.
Boot Arguments:
setenv bootargs console=ttymxc1,115200 init=/init video=mxcfb0:dev=lcd,CLAA-WVGA@60,bpp=18,if=RGB666 video=mxcfb1:off fbmem=10M vmalloc=400M androidboot.console=ttymxc1 androidboot.hardware=freescale
Timing in mxc_lcdif.c:
static struct fb_videomode lcdif_modedb[] = {
{
"CLAA-WVGA", 60, 480, 800, KHZ2PICOS(25000), 5, 5, 2, 2, 5, 2,
FB_SYNC_CLK_LAT_FALL,
FB_VMODE_NONINTERLACED,
0,
},
//...
}
FB configuration in board-mx6solo_RIoTboard.c:
static struct fsl_mxc_lcd_platform_data lcdif_data = {
.ipu_id = 0,
.disp_id = 0,
.default_ifmt = IPU_PIX_FMT_RGB666,
};
//...
static struct ipuv3_fb_platform_data RIoTboard_fb_data[] = {
{
.disp_dev = "lcd",
.interface_pix_fmt = IPU_PIX_FMT_RGB666,
.mode_str = "CLAA-WVGA",
.default_bpp = 18,
.int_clk = false,
},
//...
}
Pin Muxing in board-mx6solo_RIoTboard.h:
/* DISPLAY */
MX6DL_PAD_DI0_DISP_CLK__IPU1_DI0_DISP_CLK,
MX6DL_PAD_DI0_PIN15__IPU1_DI0_PIN15, /* DE */
MX6DL_PAD_DI0_PIN2__IPU1_DI0_PIN2, /* HSync */
MX6DL_PAD_DI0_PIN3__IPU1_DI0_PIN3, /* VSync */
//MX6DL_PAD_DI0_PIN4__IPU1_DI0_PIN4, /* Contrast not connected*/
MX6DL_PAD_DISP0_DAT0__IPU1_DISP0_DAT_0,
MX6DL_PAD_DISP0_DAT1__IPU1_DISP0_DAT_1,
MX6DL_PAD_DISP0_DAT2__IPU1_DISP0_DAT_2,
MX6DL_PAD_DISP0_DAT3__IPU1_DISP0_DAT_3,
MX6DL_PAD_DISP0_DAT4__IPU1_DISP0_DAT_4,
MX6DL_PAD_DISP0_DAT5__IPU1_DISP0_DAT_5,
MX6DL_PAD_DISP0_DAT6__IPU1_DISP0_DAT_6,
MX6DL_PAD_DISP0_DAT7__IPU1_DISP0_DAT_7,
MX6DL_PAD_DISP0_DAT8__IPU1_DISP0_DAT_8,
MX6DL_PAD_DISP0_DAT9__IPU1_DISP0_DAT_9,
MX6DL_PAD_DISP0_DAT10__IPU1_DISP0_DAT_10,
MX6DL_PAD_DISP0_DAT11__IPU1_DISP0_DAT_11,
MX6DL_PAD_DISP0_DAT12__IPU1_DISP0_DAT_12,
MX6DL_PAD_DISP0_DAT13__IPU1_DISP0_DAT_13,
MX6DL_PAD_DISP0_DAT14__IPU1_DISP0_DAT_14,
MX6DL_PAD_DISP0_DAT15__IPU1_DISP0_DAT_15,
MX6DL_PAD_DISP0_DAT16__IPU1_DISP0_DAT_16,
MX6DL_PAD_DISP0_DAT17__IPU1_DISP0_DAT_17,
Does 18-bit color just look this bad?
I think I've nearly got it!
SteveRathjen was correct about adding a 330 Ohm resistor inline with the CLK signal. That improved the image dramatically.
Then using the patches louiskoziarz recommended as a guide I changed the CLK pin strength, I bumped the control type up to PAD_CTL_DSE_240ohm and have a nearly perfect image. Although there are still a few errant blue pixels.
I have asked my coworker to add pads for inline resistors on all the display lines for the next version of our board. I'm sure that tuning those values and the pin strengths will help us get a perfect image.
Thanks to everyone for their help!
I think I've nearly got it!
SteveRathjen was correct about adding a 330 Ohm resistor inline with the CLK signal. That improved the image dramatically.
Then using the patches louiskoziarz recommended as a guide I changed the CLK pin strength, I bumped the control type up to PAD_CTL_DSE_240ohm and have a nearly perfect image. Although there are still a few errant blue pixels.
I have asked my coworker to add pads for inline resistors on all the display lines for the next version of our board. I'm sure that tuning those values and the pin strengths will help us get a perfect image.
Thanks to everyone for their help!
My board (Embest Tech RIoTboard) doesn't have any inline resistors on any of the lines.
I took a look at the schematic for the Sabre Lite. It doesn't have any resistors on the data lines but the schematic shows a mystery resistor on the CLK line. Is it just a 0 Ohms resistor? Should I have a resistor on my clock line?
The SabreSD has these 33 ohm resistors. I included them on my custom board, but changed CLK resistor to 330 ohm - the noise on the display looked VERY similar to what you see with 33 ohm on the CLK. I'm using a display with a HX8264 and 24bit. The noise when connecting the LCD to the SabreSD was 10x compared to my custom board, but I had several "adapters" to get the LCD connected to the SabreSD.
I'd seriously consider trying a resistor 33-330ohm on the CLK line if it's not too much hassle.
Hope that helps!
Steve
Yes that's how I have them wired up.
I saw another post where some said that in the boot arguments should have bpp = 32 instead of bpp = 18. I changed that and it helped most of the image but there are still certain colors it refuses to display properly.
When I display the following image...
...certain colors just appear as green.
That leads me to believe it's some sort of encoding problem, rather than a timing problem.
Well it turns out the vendor has put up linux source since I last checked. I built an image configured for my LCD but found that I still have the same colour issues. This distribution is using the same kernel and drivers as the Android image did.
So I can at least rule out the OS as the source of the problem. It's either in the kernel video drivers, the hardware lines or the LCD initialization settings.
