External Signals/Hardware Configuration for USB OTG Interrupt - i.MX RT1050

[evelynsabbag]

What specific hardware/signals generates an interrupt for the USB OTGx IRQ? The eval board (MIMXRT1050-EVKB) has the following signals connected as inputs: USB_OTG1_ID, USB_OTG1_OC, USB_OTG1_DN, USB_OTG1_DP. There aren't any good test points with which to monitor the signals with a scope and I can't see what combinations of signals generate an interrupt. The examples I've implemented are: evkbimxrt1050_dev_cdc_vnic_freertos and evkbimxrt1050_dev_cdc_vcom_freertos. These work, I can trigger on the IRQ handlers, but I can't see how they synchronize with the interrupt trigger.

My reason for needing understanding in greater detail is that I am implementing USB-C on a proprietary board, which implements the USB via an external USB controller, STUSB1600 (this handles all the USB-C specific stuff) and the 1051 variant. There is no ID line on USB-C, but the STUSB1600 generates an ATTACH signal, which I've connected to the OTG1_ID input to the MCU, however I'm not seeing an interrupt. 

Can someone explain what combination of external signals triggers the USBINT?

Thank you for the help! 

[evelynsabbag]

Turns out, the USB_OTG1_OC pin (External Input for VBUS over current detection, IMXRT1050RM, pg 2251 - only discussion found), is being used as an ATTACH line, which starts the USB communication. I'd recommend an update to the reference manual that explains the function of this pin as well as a re-labeling.

[FelipeGarcia]

Hi Evelyn,

I am sorry for the delayed response and thank you for the updated information. We will try to add this in documentation for future releases. Thanks for your feedback.

Best regards,

Felipe

[evelynsabbag]

Thank you, Felipe. Glad to contribute!

Regards,

Evelyn Sabbag

<mailto:evelynsabbag@aol.com> evelynsabbag@aol.com

617-816-5778

[evelynsabbag]

Upon further searching, I found this passage in the IXRT1050RM.pdf (IMXRT 1050 Reference Manual): 

9.9.1.2 IOMUX configuration for USB
The interface signals of the UTMI PHY are not configured in the IOMUX. The UTMI
PHY interface uses the dedicated contacts on the IC. See the chip data sheet for details.

What chip data sheet? The data sheet for the MCU (IMXRT1050IEC.pdf) doesn't go into any detail. If for the UTMI PHY, what specific variant/manufacturer, etc?

Really appreciate any help on this.