Fickle HDMI issue with Beaglebone Black

[Hilmar Lapp]

A BeagleBoard.org BBB (Rev C) I recently bought is having some very odd HDMI display issues. The connected HDMI display (a Samsung TV) works completely fine with it when the board has been off for a while, and I power it on with the display connected over the HDMI cable.

If, however, I shutdown the board (sudo shutdown -h now; or sudo halt), and power it back on within a short amount of time (I've tried a few seconds to about a minute to two), the display shows "Not a supported mode" after a short time into booting. The Linux penguin from the startup never shows up in this case. Switching to text display from X and back (using ctrl-alt-f1, ctrl-alt-f7) have no effect whatsoever (i.e., no text terminal will show on the display either), nor does restarting X. This is consistent with this not being an issue with the X server, but with the HDMI display long before any X display is started, as suggested by the penguin - or any other output from the board - failing to show. I've also now tried adding "video=HDMI-A-1:720x480@60" to /boot/uEnv.txt, as well as other suggestions in http://elinux.org/Beagleboard:BeagleBoneBlack_HDMI (including forcing a resolution). All to no avail.

I can induce this issue reproducibly with the conditions described - it's not random. The only way I know to recover from it are either (1) leave the board powered off for long enough (I know an hour suffices, haven't worked out the exact time interval yet that will make the difference between failure and success), or (2) *reboot* (sudo reboot; not shutdown -h). Pressing the reset button will *not* do the trick. Sometimes it takes several reboots in a row to recover. (The max I've needed so far is 3 reboots.)

This board is one of 3 BeagleBoard.org BBBs I recently bought, presumably all from the same batch. I have a forth one, from an Element14 batch. All 4 run the same image at the same version with the same kernel (Debian Wheezy 7.9, kernel 3.8.13-bone79, all software upgraded and current, starting image was the March 1 Debian Wheeze 7.8 image posted on beagleboard.org/latest-images). This board is the only one that has the fickle HDMI issue. The HDMI cable and HDMI TV display used are physically the same for all 4 boards, which I think is strong evidence that the issue is not somehow with the TV or the cable.

I'm not sure where to go from here - it's not that the HDMI display isn't working, but something seems to be amiss. I've now run through all software upgrades, and tried all applicable suggestions posted at http://elinux.org/Beagleboard:BeagleBoneBlack_HDMI. Does this sound like an RMA case, or are there other possibilities I could still pursue?

Below I'm pasting the output of 'parse-edid` and `xrandr --verbose`. Oddly enough, these outputs are entirely identical between when the HDMI and display are in the state of issue, and when it is all running fine. Go figure. If anyone can spot anything here, has had similar issues, or has suggestions for what else I could try, I'd be most appreciative.

  -hilmar

Output of parse-edid edid:

# EDID version 1 revision 3

Section "Monitor"

# Block type: 2:0 3:fc

Identifier "SAMSUNG"

VendorName "SAM"

ModelName "SAMSUNG"

# Block type: 2:0 3:fc

# Block type: 2:0 3:fd

HorizSync 30-68

VertRefresh 59-61

# Max dot clock (video bandwidth) 230 MHz

# DPMS capabilities: Active off:no  Suspend:no  Standby:no

Mode "1920x1080" # vfreq 60.000Hz, hfreq 67.500kHz

DotClock 148.500000

HTimings 1920 2008 2052 2200

VTimings 1080 1084 1089 1125

Flags "+HSync" "+VSync"

EndMode

Mode "1280x720" # vfreq 60.000Hz, hfreq 45.000kHz

DotClock 74.250000

HTimings 1280 1390 1430 1650

VTimings 720 725 730 750

Flags "+HSync" "+VSync"

EndMode

# Block type: 2:0 3:fc

# Block type: 2:0 3:fd

EndSection

Output of 'xrandr --verbose`:

Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080

default connected 1920x1080+0+0 (0xe9) normal (normal) 0mm x 0mm

Identifier: 0xe8

Timestamp:  12811

Subpixel:   unknown

Clones:    

CRTC:       0

CRTCs:      0

Transform:  1.000000 0.000000 0.000000

           0.000000 1.000000 0.000000

           0.000000 0.000000 1.000000

          filter: 

  1920x1080 (0xe9)    0.0MHz *current

        h: width  1920 start    0 end    0 total 1920 skew    0 clock    0.0KHz

        v: height 1080 start    0 end    0 total 1080           clock    0.0Hz

[doog]

is there any chance the TV interface is not recognizing the BBB has disconnected and is not providing EDID information? Maybe just moving the TV to another input and then back again will reset the TV HDMI input?  Shouldn't the EDID output be showing more than one supported mode? That's what's leading me to believe the TV is stuck or something.

[Hilmar Lapp]

I think the TV is recognizing the BBB has disconnected - it says searching for signals when the BBB is powered off or between boots, as it always says when there is no signal on the HDMI input.

I wish moving the TV to another input would resolve this - it was among the first things I tried, but to no avail. It seems that based on what I’m seeing it’s not the TV that does something odd (and if it did, it would more likely do that too with the other boards, I would assume), but it’s the HDMI on the board that does. If there were a way to “reset” the HDMI interface on the board, I’d try that, but I haven’t found one yet.

The EDID is indeed showing more than one supported mode - see the “1920x1080” and the “1280x720” modes in the output I enclosed in my original post.

  -hilmar

On Jan 1, 2016, at 11:39 AM, doog <doug....@gmail.com> wrote:

is there any chance the TV interface is not recognizing the BBB has disconnected and is not providing EDID information? Maybe just moving the TV to another input and then back again will reset the TV HDMI input?  Shouldn't the EDID output be showing more than one supported mode? That's what's leading me to believe the TV is stuck or something.

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Hilmar Lapp -:- lappland.io

[doog]

ok, then maybe some of the things I used to do as a tech will help. I used to use the ole finger on critical parts in the area of question and see what/if something changes. This was easier to see on/with analog systems but digital streaming or debug looping could be used for digital circuits. And done leave out capacitors but I would address components in a logical fashion to help isolate was was just added capacitance to the circuit and what was solder joint issues.

I also used a spray can to freeze/cool areas to see if components were susceptible to temp changes and out of spec or on edge of failure.

Doug