Replacing Debug serial with normal UART

[Gorgo90]

@KevinFFF

Channel 7 → TX ?
Channel 5 → RX ?

Correct.

@KevinFFF

Why your signal is 2V rather than 3.3V?

Good question. I wonder why, but at least it’s more than 1V and closer to 3.3V.
I checked with the analyzer and ttyTHS0 TX (uarta@3100000 (serial0)) is actually 3.2V.

@KevinFFF

Are you shorting TX/RX for loopback test now?
If so, you should get the same signal for TX and RX.
It seems the issue coming from no signal on RX rather than Orin NX not recognize the data.

No, sorry, I could explain myself better. I wired TX and RX to the digital analyzer and I saw the RX (channel 5) was actually ~0V. Is ti correct 0V?
I only tried to send data from TX as you can see in the image.

Here a loopback test where I analyze the transmission between TX and RX on ttyS2:

As commands I did:

root@nvidia-orin-rt:/home/nvidia# stty -F /dev/ttyS2 -opost -onlcr -isig -icanon -iexten -echo
root@nvidia-orin-rt:/home/nvidia# socat - /dev/ttyS2,raw,echo=0
test

[KevinFFF]

@Gorgo90

Here a loopback test where I analyze the transmission between TX and RX on ttyS2:

From waveform, it seems the signal is expected 1.8V here.

Do you mean that you could not receive the data on RX when you are performing loopback test and see the expected waveform?

@Gorgo90

root@nvidia-orin-rt:/home/nvidia# stty -F /dev/ttyS2 -opost -onlcr -isig -icanon -iexten -echo
root@nvidia-orin-rt:/home/nvidia# socat - /dev/ttyS2,raw,echo=0
test

Please try the following commands for loopback test instead.

$ sudo su
# stty -F /dev/ttyS2 115200 raw -echo
# cat /dev/ttyS2 &
# echo "test" > /dev/ttyS2

[Gorgo90]

@KevinFFF

From waveform, it seems the signal is expected 1.8V here.

Correct. I don’t know if It’s intentional or not. I even tested a ttyS0 serial debug pins on a different TX2 Connecttech carrier board (just for testing) and even there TX and RX were 1.8V. It used a Jetpack 4 and I could exploit ttyS0 as UART there.

@KevinFFF

Do you mean that you could not receive the data on RX when you are performing loopback test and see the expected waveform?

Exactly. With a loopback test I don’t see data on RX and I don’t see the expected waveform, correctly shown in TX waveform.

@KevinFFF

Please try the following commands for loopback test instead.

I retried with stty/cat/echo but I still don’t see any output nor waveform.

Thank you!

[KevinFFF]

Do you have the devkit could reproduce the same issue? (Orin NX + Orin Nano devkit(p3768))

[Gorgo90]

Unfortunately not at the moment.
We have a Seeedstudio reComputer J401 Carrier Board if it’s a compatible test as the Orin Nano devkit.

[KevinFFF]

Are the changes you shared in 1/Nov. all you have done?
Maybe I could try to reproduce and verify on the devkit.

[Gorgo90]

If you want to check why is not flashing correctly with the kernel changes, yes follow 1/Nov post.
If you want to check directly the serial problem with a flashed Image, follow 4/Nov Replacing Debug serial with normal UART - #12 by Gorgo90

Thank you!