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IMX6UL USB OTG HID enumeration failure

Question asked by Alberto Lubeiro on Feb 1, 2016
Latest reply on Feb 11, 2016 by Luis Casado

Hi all,


I am working with an IMX6UL in a custom design and the issue i am facing to is that the PC detects but does not recognize the board as a HID device. (see "Fallo USB.jpg")

After having read some info about the USB requirements (USB High Speed Receiver Sensitivity) i see that the squelch voltage is necessary to be above 100mV.

Please find attached a couple of graphics of the MCIMX6UL-EVK and also of my board so you can make a comparative.124059.jpg (our custom board) and 124826.jpg (MCIMX6UL-EVK)

Here you can see that in our design, the squelch voltage is 90mV and in MCIMX6UL-EVK is over 120mV

Our VDD_USB_CAP voltage which comes from LDO_USB is 2.40V and in the MCIMX6UL-EVK it is 2.7V. The reference manual says that this voltage should be 3V. Don't know if our voltage is insufficient and therefore the cause of our problem.


Please find attached also our scheme "Esquema USB.jpg" the things inside red circles are DNP

We have also made the test of connecting the MCIMX6UL-EVK to the PC through our PCB and it works fine (see picture 100429.jpg). This was an attempt of seeing if our 120 ohms of diff impedance or our layout was influencing.


Any help will be apreciated.

Thanks and best regards