BBG wo'nt boot with P8_29~46 connected to expansion connector

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Charles Chao

Aug 7, 2019, 2:57:24 AM8/7/19
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Hi, All.
I connect the Beaglebone Green with expansion connectors to fully utilize all gpio pins. (possible 65 gpio's)
To avoid eMMC conflict, not to use P8.3~6,P8.20~25, since my BBG was booted from eMMC. 10 pins gone.

As shown in the picture 1, I can not boot BBG but with only power led on.
Remove connector (pins P8.39~46), then I got BBG boot with all leds on but my notebook says the USB unknown device can't function.
After remove the other connector (pins P8.29~38), then I got all normal boot and functioning.

So how can I use the SYS_BOOT 16 PINS as GPIO's, which corresponding to P8_31~46 pins of BBG !
from BBB SRM Rev.C.1
If BBB can use all these SYS_BOOT pins for hdmi lcd, so can BBG uses these pins as gpio's? 

Thanks in advance.



Aug 7, 2019, 11:18:16 AM8/7/19
to BeagleBoard
During boot the pins have to have the default configuration, and the wired hardware must not influence the state of the pins.

After boot, you can configure the desired pinmuxing and connect your hardware.

BTW: since you're booting from EMC, you can use 6 further GPIOs on the SD-Card slot and 2 further on the JT header (unidirectional).


Pranav Kumar

Aug 7, 2019, 11:51:11 PM8/7/19
to BeagleBoard
I just want to ask that what are you doing by using so many gpios of BBG ,
1. if you are using it as a I/O Pins or something else.

Charles Chao

Aug 8, 2019, 12:10:40 AM8/8/19
to BeagleBoard
Thank you for the tips.

I have unplug the other ends of both connectors that fail the boot then I got BOOTUP!!

It turn out to be the  3.3V lead of MW MPM-15-3.3 SMPS(switch mode power supply) is nearly short with the ground lead when it is inactive.

So I have to unplug the 3.3V lead when I boot the BBG or find other 3.3V 3.5A power supply.


TJF於 2019年8月7日星期三 UTC+8下午11時18分16秒寫道:
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