Reconnect HDMI Every Time I Power On?

I’ve ordered the BeagleBone Black and am looking forward to getting it in on Friday. I’ve been drinking from the firehose of the manual and schematics in the meantime.

Regarding the connection of the HDMI interface during power-on in “stand-alone” configuration; there is a big red note in section 3.4.2 Step #1 of the System Reference Manual. It says, “NOTE: Do not plug in the cable to the board until after the board is powered up.” Then in steps #5-7, I do the following:

#5: Connect 5V power
#6: Connect HDMI device
#7: Wait for boot to complete


(a) Do I need to plan to physically disconnect HDMI device every time I power the BeagleBone Black OFF and the reconnect after each time I power ON again using 5V jack power?

(b) Does the answer to (a) also apply when I use the power button instead of the 5V DC power input?

© Why is this highlighted in red? What is the possible negative consequence if I fail to do this? It seems like the HDMI interface on the BeagleBone Black (schematic page 10) is all outputs. So I’m guessing maybe the HDMI device just gets confused… or is there an issue of possible damage to the BeagleBone or to the HDMI device?

This is a test to see if the monitor is trying to power the board over HDMI via the EDID path. If you see no issues you can plug in the cable before power up. No issue.


So I think you are referring to the possibility of power being supplied to the SYS_5V rail through P6-19. So basically, the test procedure would be:

(1) Plug in 5V power cable.
(2) Plug in HDMI cable
(3) Wait for everything to boot up
(4) If it BB fails to boot, see if RT1 tripped due to a possible difference in competing 5V supply rails.
(5) If BB boots all the way, remove 5V power cable.
(6) If board is still running OR if RT1 trips at that point, then I know monitor is trying to power board. Otherwise, I’m good to just leave it connected from that point forward.

Is that a fair test?

No I am not. The +5V rail on the HDMI connector.