I have an Edgeport USB to 4xRS232 converter which booted up the system normally when RPi B+ was turned on couple of years ago when I set it up. Nowadays, the booting hangs up on rainbow screen. If I disconnect the USB cable to Edgeport and let the RPi boot, it boots up normally. When the RPi is completely booted up and I plug the USB cable to Edgeport it works normally as well. Obviously the problem is that current consumption is too high if USB cable to Edgeport is plugged in when RPi is turned on.
I have already tested boot_delay=3 and max_usb_current=1 in my config.txt without any help. I have not yet tested HW modication to minimase the current limitation.
I assume my PSU provides enough current to the system.
I'm wondering if there is any software configuration option to delay the USB power on ?
Does the boot_delay=3 turn on the power to USB immediately when RPi is turned on?