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!