How to Update VU8C EDID

Start I2C bus driver using i2c-dev module to setup interface for writing the EDID binary via HDMI DDC.
The I2C driver module can be different for Host PC specification.

$ sudo modprobe i2c-dev

Then, install some utilities.

# sudo apt-get install i2c-tools
# sudo apt-get install python-smbus
# sudo apt-get install edid-decode

Using i2cdetect and i2c device nodes, all the i2c busses can be found.

$ ls /dev/i2c*
/dev/i2c-0  /dev/i2c-10  /dev/i2c-12  /dev/i2c-14  /dev/i2c-16  /dev/i2c-18  /dev/i2c-3  /dev/i2c-5  /dev/i2c-7  /dev/i2c-9
/dev/i2c-1  /dev/i2c-11  /dev/i2c-13  /dev/i2c-15  /dev/i2c-17  /dev/i2c-2   /dev/i2c-4  /dev/i2c-6  /dev/i2c-8

$ i2cdetect -l
i2c-0        unknown           i915 gmbus ssc                          N/A
i2c-1        unknown           i915 gmbus vga                          N/A
i2c-2        unknown           i915 gmbus panel                        N/A
i2c-3        unknown           i915 gmbus dpc                          N/A
i2c-4        unknown           i915 gmbus dpb                          N/A
i2c-5        unknown           i915 gmbus dpd                          N/A
i2c-6        unknown           DPDDC-B                                 N/A
....
....
i2c-18        unknown           nouveau-0000:01:00.0-29                 N/A

In my case, bus#4 is assigned to HDMI channel that is connected to VU8C.

The command, get-edid scans potential buses that handle EDID.
The below example shows bus#2 (Main monitor) and bus#4 (Connected to VU8C).

$ sudo get-edid
This is read-edid version 3.0.1. Prepare for some fun.
Attempting to use i2c interface
No EDID on bus 0
No EDID on bus 1
No EDID on bus 3
No EDID on bus 5
...
...
No EDID on bus 18
2 potential busses found: 2 4
Will scan through until the first EDID is found.
Pass a bus number as an option to this program to go only for that one.
128-byte EDID successfully retrieved from i2c bus 2
������0�
�#x
՞YP�&PT















6��p8@0 5Y�6��p8@0 5Y��C088T�156WF1


Looks like i2c was successful. Have a good day.

To write EDID binary and read-back it, we use the utility edid-rw and edid-decode.
https://github.com/bulletmark/edid-rw

Please download source codes from the github and build it.

# git clone https://github.com/bulletmark/edid-rw
# cd edid-rw
# make

$ sudo ./edid-rw 4 | edid-decode
Extracted contents:
header:          00 ff ff ff ff ff ff 00
serial number:   21 6c 30 00 01 00 00 00 0a 14
version:         01 03
basic params:    80 10 0c 78 0a
chroma info:     cf 74 a3 57 4c b0 23 09 48 4c
established:     21 08 00
standard:        61 40 45 40 61 40 95 00 01 01 01 01 01 01 01 01
descriptor 1:    64 19 00 22 41 00 26 30 14 0a 44 00 a0 78 00 00 00 1e
descriptor 2:    64 19 80 22 41 00 26 30 14 0a 44 00 a0 78 00 00 00 9e
descriptor 3:    00 00 00 fc 00 4d 53 74 61 72 20 44 65 6d 6f 0a 20 20
descriptor 4:    00 00 00 fd 00 32 4b 1e 50 12 00 0a 20 20 20 20 20 20
extensions:      00
checksum:        50

Manufacturer: HKL Model 30 Serial Number 1
Made week 10 of 2010
EDID version: 1.3
Digital display
Maximum image size: 16 cm x 12 cm
Gamma: 2.20
Supported color formats: RGB 4:4:4, YCrCb 4:2:2
First detailed timing is preferred timing
Established timings supported:
  640x480@60Hz
  800x600@60Hz
  1024x768@60Hz
Standard timings supported:
  1024x768@60Hz
  800x600@60Hz
  1024x768@60Hz
  1440x900@60Hz
Detailed mode: Clock 65.000 MHz, 160 mm x 120 mm
               1024 1044 1054 1314 hborder 0
                768  772  776  806 vborder 0
               +hsync +vsync
Detailed mode: Clock 65.000 MHz, 160 mm x 120 mm
               1152 1172 1182 1442 hborder 0
                768  772  776  806 vborder 0
               +hsync +vsync interlaced
Monitor name: MStar Demo
  Monitor ranges: 50-75HZ vertical, 30-80kHz horizontal, max dotclock 180MHz
Checksum: 0x50

Please refer to the following to download edid_vu8c.bin.
Download edid_vu8c.bin
or

wget http://dn.odroid.com/edid_vu8c.bin

Before writing EDID binary, please make sure the I2C device node.

The usage of edid-rw is as following.

$ edid-rw  -w  [bus no.]  < [edid binary]

In my case, the bus node to VU8C is bus#4.

$ sudo ./edid-rw -w 4 < edid_vu8c.bin 

Then, using the following commands, you can check if it's completely done.

$ sudo ./edid-rw 4 | edid-decode

Also, you can confirm it using xrandr.

$ xrandr 
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
LVDS1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 345mm x 194mm
   1920x1080      59.9*+
...
...
   800x600        60.3     56.2  
   640x480        59.9  
DP1 disconnected (normal left inverted right x axis y axis)
HDMI1 connected (normal left inverted right x axis y axis)
   1024x768       61.4 +   60.0  
   1440x900       59.9  
   1152x768i     111.9  
   800x600        60.3  
   640x480        60.0  
VGA1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis