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Question about USB Host power up timing

Question asked by Marco Lam on Jun 10, 2019
Latest reply on Jun 13, 2019 by Marco Lam

Dear All,

 

I am working with a custom iMX 7D Board referenced to iMX7D Sabre Rev D Board.

An external USB device is expect to connect to USB Host.

 

I would like to delay the detection of the USB device after most of the /etc/init.d scripts had been executed.

 

The board is using the same IC (SP2526A) and USB_OTG2_PWR is connected to GPIO1_IO07 as same as the Sabre board.

 

Looking into the device tree and the "regulator-fixed" driver, I tried to add "startup-delay-us" with different values.

I also added some debug prints around the delay with help me to verify with debug messages.

 

However, with the help of oscilloscope, I found that even the system is "correctly" sleeping during the delay, the signal level of USB_OTG2_PWR had already been pulled-up before the delay start.

 

Not sure if I had set anything incorrectly or misunderstood the usage of this property.

If I wish to achieve my goal, are there any alternative method?

Please help to advise.

 

Thanks

Marco

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