Kinetis: how USB attachment is detected?

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Kinetis: how USB attachment is detected?

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huishao2
Contributor IV

Hi

I have k20d72m based USB host and k20d50m based USB device. I am just wondering how the USB attachment event is triggered on host USB controller? There are two different cases: powering on the host with device plugged in and pluging in the device after host is powered on. What are the differences there?

Reading through some books, it seems like the pulled up D+ from device is the reason for attachment event. But I don't see any pullup on D+ from my USB device design.

Thanks!

Hui

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Paul_Tian
NXP Employee
NXP Employee

Hi, Shao Hui

For case owering on the host with device plugged in, MCU will not receive attach interrupt. For case pluging in the device after host is powered on, MCU will receive attach interrupt. This is the difference from MCU side.

Hope this reply can help you. Thanks.

Best Regards

Paul

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huishao2
Contributor IV

Hi Paul

Thanks for reply.

For interrupt case, what is the signal that actually causes the interrupt/event upon attachment?

Hui

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Paul_Tian
NXP Employee
NXP Employee

Hi, Hui

Sorry, I cannot find your attachment. Thanks.

Best Regards

Paul

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huishao2
Contributor IV

Hi Zhe Tian

Basically what I want to understand is the difference between booting up host with USB plugged in and plugging in USB after host bootup, in terms of enumeration process.  That would help on my debugging work.

thanks!

Hui

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