UART signal problem

[CristianM]

Hello. I am using the NanoPi NEO Core board to communicate via UART1 and UART2 ports. I configure the ports using Python - pyserial. This is my configuration code:

Code: Select all

import serial
com = serial.Serial(
            port = '/dev/ttyS' + str(port),
            baudrate = 115200,
            parity = serial.PARITY_NONE,
            stopbits = serial.STOPBITS_ONE,
            bytesize = serial.EIGHTBITS,
            timeout = 0.02
            )

The problem is that the UART TX signal is not clean, as you can see from the following pictures:

https://ibb.co/5sdvGVf

https://ibb.co/zfgZrGT

I get the same signal on both UART ports. I also confirm that I get a similar signal even when the UART TX pin is floating, which leads me to think it may be a software or UART interface problem.

Does anybody have a clue what the problem is?

[igorp]

Use those resources for start:

https://docs.armbian.com/User-Guide_Armbian_overlays/
https://github.com/bitbank2/ArmbianIO
https://forum.armbian.com/
https://github.com/sgjava/java-periphery
https://groups.google.com/g/linux-sunxi

[CristianM]

Use those resources for start:

https://docs.armbian.com/User-Guide_Armbian_overlays/
https://github.com/bitbank2/ArmbianIO
https://forum.armbian.com/
https://github.com/sgjava/java-periphery
https://groups.google.com/g/linux-sunxi

Hi. Can you please detail what I should look for? Regarding the device tree overlays, I don't think any modification is needed because I can access the UART ports from /dev/ttys*. And the libraries suggested do not contain any support for UART in Python.

[igorp]

Hi. Can you please detail what I should look for? Regarding the device tree overlays, I don't think any modification is needed because I can access the UART ports from /dev/ttys*. And the libraries suggested do not contain any support for UART in Python.

Sorry, I am not working or using UARTS on sunxi devices at this moment. Also don't remember when I have hooked scope to those pins ... I am just pointing you to better source of knowledge and people that know stuff and you can try talking to. Perhaps it's a known problem already solved? All those interfaces are identical on all boards with this (Allwinner H3/H5) chip. And there are many of them ...

[CristianM]

Thank you. I have posted my question on the Armbian forum also. Maybe somebody there has an advice.

[CristianM]

It turns out it was a problem with the oscilloscope.