Ubuntu 18.04.05 wont boot with GPIO connected

[Zarbokk]

I am connecting my Pixracer(a flight Computer for a drone) to the GPIO pins of a raspberry pi 4 4gb. I am using TX RX and ground.
The OS is Ubuntu 18.04.05 64 bit.
I sadly have to use Ubuntu for other programs.

If I connect them together, the pi won’t boot at all.
If the pi is booted without the cables attached, and the cables are connected later the connection to the Pixracer works great and everything is fine. Until I try to reboot.


With raspberry OS I do not have that problem and everything works fine.

Any idea?
My current plans for tomorrow are:
- trying out 32 Bit Ubuntu
- maybe turn the GPIO pins off and turn them on “later” if that is even possible

Any help would be great;)

[larryr]

My guess is you do not have enough power on your Pi to run it.
Try a bigger power supply. If you have too much draw the CPU cannot boot.

[Zarbokk]

That was our first thought as well. But even with a Lab-Power supply he will not boot at all.

Especially that it is booting with raspberry OS is weird...

[larryr]

New thought,
GPIO pins 8 and 10 connected might cause the Ubuntu Loader to think you have a console terminal attached and its waiting for input from the terminal or it's getting garbage from the controller and does not know what to do next. Many old Unix Computers from the 1970's did that if it detected a console on a certain port was turned on.
You might have to put them on a relay to connect them via gpio pins 37 and 39 to enable the relay after the boot.

My second way to fix this is with an RS-232 USB dongle. That way the gpio is not used. but you will have to select the USB RS-232 and set the baud rate for it.

My 2 cents.