Incorrect device overlay selected during boot

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richa...@yahoo.com

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Jun 30, 2016, 9:24:32 AM6/30/16
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Hi,

My BBB stack has a 4.3" LCD cape -- powerup diagnostics (dmesg) indicated the cape was found OK & brightness worked Ok. I was unable to view (startup) text on the display. (Ver 4.4.1-bone11). After a few days of debug, I found that the MuxPins were not properly updated and were still accessing HDMI (not modified as expected). I added an 'echo' into /uEnv.txt & discovered that the 'overlay file' was not right - it was the default chosen at power-up.

/boot/uEnv.txt has the lines (amongst others)

     dtb=am335x-boneblack-overlay.dtb
     Disable: HDMI

/uEnv.txt was modified - fdtfile was replaced by dtb

    #loadxfdt=load mmc 0:1 ${fdtaddr} /boot/dtbs/${uname_r}/${fdtfile}
    loadxfdt=load mmc 0:1 ${fdtaddr} /boot/dtbs/${uname_r}/${dtb}

Possibly modifying fdtfile is the appropriate method -- Is there a better solution?

thx

William Hermans

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Jun 30, 2016, 1:35:23 PM6/30/16
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Yeah, you're modifying the wrong file.

debian@beaglebone:~/nfs$ cat /boot/uEnv.txt
#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0

uname_r=4.4.12-ti-r31
#uuid=
#dtb=

##BeagleBone Black/Green dtb's for v4.1.x (BeagleBone White just works..)

##BeagleBone Black: HDMI (Audio/Video) disabled:
dtb=am335x-boneblack-emmc-overlay.dtb

. . .

dtb=am335x-boneblack-emmc-overlay.dtb is the line you're after, and it probably is proceeded by a pound( # ) symbol. So it's commented out. SImply remove the # to uncomment, and then reboot the board.


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