USB power on BelaMini should come from Vsys 5V

giuliomoro commented 5 years ago

On the PB:

1) VBUS.RAW (the 5V in from the µUSB on the PB) is connected through a ferrite bead (FB1) to the VIN.USB signal (broken out on P1.07 and labelled USB1.VIN). This is also connected to ball J16 of the BGA, which is USB0_VBUS. This has the following consequences:

if power is supplied through USB0 (µUSB on the PB), then USB1.VIN will also be powered.
if power is supplied through USB1 (header), then the AM335x will think that USB0 has power.

2) the OSD335x checklist (https://octavosystems.com/app_notes/osd335x-schematic-checklist-am335x/) says

USB VBUS Sense Input: USBx_VBUS is a voltage sense input and NOT a power output pin. Check that a valid voltage (>=4.4V) is present on the pin to enable the USBx peripheral.

3) the TPS65217 can allow large currents from input to the Vsys output, and ranges can be set in software:

4) Jason K is happy to review the amended design.

giuliomoro commented 5 years ago

This https://github.com/beagleboard/capes/blob/master/pocketbeagle/GamePup/GamePup_Cape_sch.pdf , according to Jason, "should do USB host right" (and uses a boost converter to generate the right 5V for USB regardless of the VIN/VBAT input voltage).

giuliomoro commented 5 years ago

from https://octavosystems.com/app_notes/osd335x-design-tutorial/osd335x-lesson-2-minimal-linux-boot/osd335x-lesson-2-usb-circuitry/

USBx_DP/DM: These are differential I/O pins that carry data. USBx_DRVVBUS: The USB peripherals themselves cannot supply the necessary current to support Host mode. Therefore, the USBx_DRVVBUS output pin was provided to control external 5V power logic used to supply power to a Host port. USBx_VBUS: This input pin is used to sense the voltage of the VBUS pin . For the USB peripheral to be enabled, a valid voltage (>=4.4V) should be placed on this pin. USB_ID: The mode of USB peripheral depends on the state of this pin.

BelaPlatform / bela-hardware

USB power on BelaMini should come from Vsys 5V #9