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Advanced users • How to boot U-Boot over alternative UART

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I am trying to get U-Boot running on my raspberry pi 4B. I am not worried about getting a linux kernel etc loaded, just the u-boot shell. Unfortunately, my GPIO pins 14/15 are fried (confirmed with gpiotest: https://elinux.org/R-Pi_Troubleshooting#Testing) I also cannot seem to get UART0 working on other pins, so I'm assuming it's fried too.

I believe it should be possible to boot on another UART. I have tried changing the options in U-Boot's menuconfig (CONFIG_CONS_INDEX), and I have also tried editing the dts files, or config.txt (I recently read that apparently U-BOOT will ignore the config.txt overlays unless it is specifically set otherwise?). In any case I'm not getting any output on the alternative pins. It's extremely hard to debug since I have no logs or anything, only a single bit of information: did it output on the serial or not.

I found this thread about the orange pi which seems like it might be similar: https://forum.armbian.com/topic/11301-c ... gepi-zero/ but it didn't seem to work for me.

Does anyone have experience changing the boot UART on U-BOOT, or otherwise know what I need to do to get it working?

Statistics: Posted by jeremysalwen — Wed May 15, 2024 11:03 pm — Replies 0 — Views 19



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