Linux USB ports

RE: Linux USB ports

amelio — Fri, 09 Jan 2026 08:09:21 GMT

Hi Simon,

I am going to ask our HW specialist, as I am a SFW developer .. I will keep you posted.

thanks

Amelio

RE: Linux USB ports

Simon D-M — Fri, 09 Jan 2026 08:06:54 GMT

Hi,

I might be wrong, but I don't see any ground sharing between the DK and the driver module. Can you confirm it ?

If you indeed don't have any ground sharing, can you please connect both GNDs.

Best regards,

Simon D-M

RE: Linux USB ports

amelio — Fri, 09 Jan 2026 07:57:36 GMT

RE: Linux USB ports

amelio — Thu, 08 Jan 2026 17:18:27 GMT

Hi Simon, I tried to resend the pic (using the INSERT label) but maybe I cannot follow the right way, could you please help me ?

RE: Linux USB ports

Simon D-M — Thu, 08 Jan 2026 14:22:21 GMT

Hi,

[quote user="amelio"]below a picture of system.[/quote]

I think you didn't send the picture. Can you please resend it ?

[quote user="amelio"]my colleague told me the current can be up 500 mA so we are very close to Linux limit[/quote]

I think it would then be a good idea to measure the power usage to see it there are some amperage issue or some voltage drop. Maybe a capacitor close to the screen / driver can do the trick.

Best regards,

Simon D-M

RE: Linux USB ports

amelio — Wed, 07 Jan 2026 12:19:46 GMT

Hi Simon,

1) The computer is the same (a desktop machine). Windows is version 11, Linux is Ubuntu 24

2) my colleague told me the current can be up 500 mA so we are very close to Linux limit

3) below a picture of system. I don't have the code right now as it is under development by a colleague. I can ask him if you consider it very important.

RE: Linux USB ports

Simon D-M — Mon, 05 Jan 2026 15:03:44 GMT

Hi,

[quote user="amelio"]The Maximum power command gives (BTW the ID is 1064 and not 1055):[/quote]

My bad, apparently the product ID is not always the same everywhere. On my device, it was 1055.

[quote user="amelio"]Under MS Windows I have a serial terminal opened when it works fine. Under Linux it do not work with or without the serial terminal opened.[/quote]

When you tried on Linux and Windows did you use different computer or is it always the same one ? It may be caused by a difference between computer and not OS.

[quote user="amelio"]MaxPower 500mA[/quote]

Do you know what is the theoretical maximum value that the screen + driver should be drawing ?

It might be useful to monitor the current (and maybe even the voltage) to be sure that the problem is about the power and not something else.

Some other possibilities can be that there is a grounding issue between the screen/IT8951 and the board. Or Maybe you need a bigger capacitor for the IT8951 or the screen. There are too many possibilities to have a definitive answer there.

[quote user="amelio"]Let me know if this info is enough for your needs.[/quote]

Would it be possible to have some schematics / photos. And Maybe even a bit of code ? I can convert this ticket to private if you don't want to share them publicly (ask me first, and send the files only when the ticket is private), however if you don't mind, I would rather have the ticket public so that if someone has the same problem, the ticket can be found.

Best regards,

Simon D-M

RE: Linux USB ports

amelio — Sat, 03 Jan 2026 10:24:11 GMT

Sorry for late reply but I was abroad some days.

The screen is connected via a ribbon cable to IT8951, and the IT8951 is connected to nrf9160DK using the pins P0.31, P0.30, P0.20, GND, P0.14, P0.15, P0.16, 5 V

At the moment I cannot measure the current (if really important I will try to get a PPK2)

Under MS Windows I have a serial terminal opened when it works fine. Under Linux it do not work with or without the serial terminal opened.

The Maximum power command gives (BTW the ID is 1064 and not 1055):

$ lsusb -d 1366:1064 -v | grep MaxPower

MaxPower 500mA

Let me know if this info is enough for your needs.

Thanks

Best Regards

Amelio

RE: Linux USB ports

Simon D-M — Mon, 29 Dec 2025 14:17:15 GMT

Hi Amelio,

Can you share a bit more information about the current hardware setup ?

How do you provide power to the screen ? If you power it through the DK, which pin are you using ?

Are you able to measure the current (using a PPK2 or an oscilloscope) ? How much current is drawn ?

[quote user=""]I have a nrf9160dk that drives a screen via SPI, using an IT8951 controller.[/quote]

Are you sure the problem is on the nrf9160 side and not on the IT8951 controller? To check it, you can try to measure the SPI signals to see if there is some communication happening.

[quote user=""]The firmware driving the screen works fine if I plug the USB cable on a power bank or using MS Windows[/quote]

Do you have a serial terminal open on Windows when it works fine ? And on Linux, does it work when no serial terminal is connected ? It might be that for some reason, your serial communication is interfering with the SPI of the screen.

[quote user=""]I was thinking the problem was a lack of power on USB ports[/quote]

You can try to run the command "lsusb -d 1366:1055 -v | grep MaxPower" in a Linux terminal with the device connected. It should show you the Maximum Power requested by the SEGGER J-Link.

In my case, it shows :

$ lsusb -d 1366:1055 -v | grep MaxPower 
    MaxPower              100mA

Maybe Windows and the power bank don't care about this value and output as much current as the device wants... If this is the issue, it might be possible to make the device request more power, but I'll have to look in more detail to do so.

Tell me if any of this helped.

Best regards,

Simon D-M

RE: Linux USB ports

amelio — Sun, 28 Dec 2025 08:30:38 GMT

Thanks, but this is not the case. The data are received via LTE-M internal modem and then displayed via SPI. The USB is only used to power the board and see the debug messages on /dev/ttyACM0. I suspect that there is a difference (between Windows and Linux) in managing the power of USB port or some kind of interference between the power and the virtual ttys. With Windows or a generic USB power supply the app works fine, while under Linux (I used different flavors and releases) it works fine for all parts of the app except when it writes to screen via SPI.

RE: Linux USB ports

Achim Kraus — Sun, 28 Dec 2025 07:57:01 GMT

Maybe it's too obvious:

Does the nRF9160dk get the data from the PC via USB and then displays that via SPI on that display?

Maybe it's then just a question of the line-endings/termination. On windows it's common to use CR+LF, in unix it's only LF. The most terminal programs (both on windows and unix) offers then usually some configuration for that. Try to set that to the windows style (CR+LF) and see, if that works. If it's an application on unix, which feeds the data, try to add a "\r" before "\n".