Which system do you use? Android, Ubuntu, OOWOW or others?
Ubuntu
Which version of system do you use? Khadas official images, self built images, or others?
official emmc Ubuntu 22 gnome
Please describe your issue below:
I’ve enabled uart3 overlay according to VIM3/3L UART [Khadas Docs]
Just set fdt_overlays=uart3
at /boot/dtb/amlogic/kvim3.dtb.overlay.env
Then rebooted, got /dev/ttyS3, but pins 15 and 16 are just always high. I’ve checked it with oscilloscope.
What could be the reason?
I feel like I’m missing something or there is a missing piece in docs. So I had to create another UART issue as I’ve studied all related here, and no one actually contains the solution or even describes similar case.
I didn’t use the code, just minicom. Debug uart works fine - this is how i’ve got startup log. Any suggestions for steps to debug further? looks like maybe those pins 15,16 left gpios and not switched to uart.
Maybe i could somehow verify this?
Nope. I did not. And to prove it once again. I reflashed board with the same image (latest, i guess) checked pin 15 16 states: mode IN, V 0
Then enabled uart3 overlay, started minicom -D /dev/ttyS3 connected 14 15 16, tested with minicom from the host - not working. My ttl-usb is proved working device - i’ve read startup log from this exact VIM3 with it.
So. UART3 is not working.
gpio readall → pins 15 16 mode ALT1, V 1
disconnect pins
pin 15 goes down: V 0 pin 16 as it was V 1
Hey! I finally managed to run it. The key was the hw flow control that enabled by default in minicom.
My bad, Guys. Sorry for taking so much of your time for this mistake.