Hi there,
I want to implement a USB 2.0 DRD using peripheral interface USB1 on an AM5728 connected to a microUSB receptacle. I want use it for peripheral boot, too.
According to the AM5728 TRM ch. 24.7 "SuperSpeed USB DRD", the proper configuration for a dual-role application would be:
- USB1_DP/DM connected to microUSB receptacle
- VBUS monitoring via PMIC TPS659037x, signalling via interrupt or PMIC GPIO5
- Receptacle ID pin connected to AM572x GPIO with a pull-up to VCC of the GPIO
- USB1_DRVVBUS connected to USB supply switch enable
Questions:
1. Back in the AM335x times, a proper VBUS detection was necessary for the USB boot to happen. According to ch. 33.2.2, the ROM code does not interact with the PMIC. I guess it doesn't query the VBUS status either. Is it correct, that the minimum prerequisites for the USB boot to happen are DM/DP connected to a USB host? Anything else the boot code needs for that task besides a proper SYSBOOT strapping?
2. Why is there a pull-up on the ID signal? As far as I now, ID=GND means host, ID=open means device.
3. As I want to implement a USB 2.0 DRD, I don't need the USB 3.0 diff pairs. Is there a recommendation how to treat these if unused? Leave them floating?
Thanks for enlightenment
Wolfram Stumpf
