How to enable the internal 1.5K-ohm pull-up resister in the USB PHY?

[david9991]

In IMXRT1050 reference manual it said:

56.2.5.4 Switchable 1.5KΩ USB_DP Pullup Resistor
This product contains a switchable 1.5 KΩ pullup resistor on the USB_n_DP signal.
This resistor is switched on to indicate to the host/hub controller that a full-speed-capable device is on the USB cable, powered on, and ready. This resistor is switched off at power-on reset so the host does not recognize a USB device until the processor software enables the announcement of a full-speed device. 

but hasn’t mentioned how to enable this internal pull-up resistor, and I cannot find any external pull-up resister on the board, so my PC cannot detect if device plugged in. What should I do now?

[igorpadykov]

Hi David

usb module controls this bit automatically internally during usb connection

procedure, seems there is no way to manually in software control it.

Best regards
igor
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[david9991]

And my device does undetectable in this moment. I think USB port is just a analog detectable circuit, when the pull-up on DP or DN was detected, HOST should send the description request automatically without any other condition, even USB control not be started right? I tried use Wireshark to monitor the USB request, but nothing was captured.

[igorpadykov]

what is about other devices, USB module perform enumeration process using on own state machine,

you can try examples with i.MXRT1050 EVK and its MCUXpresso software

Welcome | MCUXpresso SDK Builder 

Best regards
igor

[david9991]

With some investigation I found the point: the RAM region have not been mark to 'shareable' in the MPU.

Thank you all the same. :smileywink:

[david9991]

But how to explain: This resistor is switched off at power-on reset so the host does not recognize a USB device until the processor software enables the announcement of a full-speed device"