Yep, you are changing the boot mode of the processor. A big no no.
https://www.elinux.org/Beagleboard:BeagleBoneBlack#Expansion_Header_Pin_Usage
Gerald
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Yes. And sys_reset_n is just a RC-delayed version of the 3V3 supply. It is not debounced
if activated by the reset switch and rises slowly in the classic
1-e-function style.
You need a Schmidt-trigger if you want to use it as a logic signal.
That sys_reset_n is high does not mean that you may drive some pins
(in my case P8. 39-46, the 8 pins accessible to PRU1 and also
used by the LCD.)
I found that I had to use an 74LVC244 for isolation; the 3stated pins of a
Xilinx Coolrunner II were not high-impedance enough.
When sys_reset_n goes away, the processor just starts; it has not yet made up
its mind where to boot from.
I used a time constant of 3 times sys_reset_n to enable the
74lvc244.
regards, Gerhard
It just take on boot pin to mess up the boot process. If it is not powered on it still presents a load. It still affects the boot pins.
Key point…DO NOT PUT ANYTHNING on GPIO pins that share the boot function on power up.
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U-Boot SPL 2017.03-00002-gd12b1519b4 (Mar 14 2017 - 10:28:26)Trying to boot from MMC2mmc_load_image_raw_sector: mmc block read errorspl_register_fat_device: fat register err - -1spl_load_image_fat: error reading image u-boot.img, err - -1 ** ext4fs_devread read error - blockFailed to mount ext2 filesystem...spl_load_image_ext: ext4fs mount err - 0
Looks like you may be conflicted with the eMMC pins, which also go to the expansion headers.
I do not know if the MMC ports are numbered 0 and 1 or 1 and 2 these days in SW. But normally the board boots from the eMMC. On the Hardware we numbered them 0 and 1, 0 being the SD card and 1 being the eMMC. You can insert a bootable SD card and see if it boots from there.
Gerald
From: beagl...@googlegroups.com [mailto:beagl...@googlegroups.com]
On Behalf Of Mike Brandon
Sent: Friday, November 30, 2018 5:09 PM
To: BeagleBoard <beagl...@googlegroups.com>
Subject: Re: [beagleboard] Beaglebone Black won't boot when gpio connections made
U-Boot SPL 2017.03-00002-gd12b1519b4 (Mar 14 2017 - 10:28:26)
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On Fri, Nov 30, 2018 at 4:38 PM Mike Brandon <smbra...@gmail.com> wrote:
>
> But which gpio am I using that is a boot pin? In the reference manual, the 16 boot pins are on the P8 header... I'm using gpios on the P9 header.
>