i.MX8ULP USB connectivity issues

[texnikk]

Greetings,

To evaluate i.MX8ULP processor for our products we're trying to build a custom devboard which is based on NXP-made SoM from MCIMX8ULP-EVK-BB devkit. 
This board exposes USB0 from MCIMX8ULP-EVK-SOM to a microUSB connector so that firmware can be uploaded using UUU utility in Serial Download mode.

Physical connectivity is quite simple (schematic screenshots attached)

But currently we're experiencing a USB connectivity issues with this board - in 90% of cases when we try to connect USB to host PC - the board is not detected. And even if it is detected - it starts to disappear and reappear. We've checked power and clocks - everything looks good, so we suspect some USB signal-related issue.

Is there any specific requirements for implementing USB2.0 connectivity with i.MX8ULP which must be obeyed for a stable and working USB (additionally to routing D+ and D- with 90 Ohm traces)?

Thanks,

Sergey

[JorgeCas]

Hello,

Could you please share the connections in i.MX side?

Did you perform a signal integrity simulation?

Best regards.

[texnikk]

Hello,

I'm attaching full schematic for USB part (Devboard-USB-PART)

SOM-USB-part is a screenshot from MCIMX8ULP-EVK-SOM-a7.pdf , which is a part of "i.MX 8ULP EVK Base Board Design Files"

Thanks,

Sergey

[JorgeCas · Accepted solution]

Hello,

Got it, thank you for the update.

As I can see, you are using our SOM and connecting it to your custom base board with Micro USB.

Please take a look in the next post, the i.MX8MM can be used as reference for i.MX8ULP.

i.MX8MM & i.MX8MQ USB2.0 Design Without USB TYPE-C - NXP Community

Best regards.