PocketBeagle USB1 Question

I note that there is a PocketBeagle pin P1-7 named USB1-VIN.

I don’t find any connection on the PB schematic, other than to P1-7.

It was connected externally in all of the USB1 host discussions and Fritzing diagrams.

The name would imply that it is a way to deliver power to the board when USB1 has an external 5 Volt power source.

I guess the basic question is whether this needs to be used/connected when USB1 is functioning as a host.

— Graham

Further research, looking at the Eagle board and schematic files for the PB, it appears that USB0.VIN and USB1.VIN are both directly connected to VIN.USB
Which explains why I had no power on my USB1 host port when connected like the Fritzing diagram, since I am powering from VIN currently.

So the question becomes,
What is the best way to power USB1 VBUS as a host if I don’t know in advance whether the customer application will run from VIN or VIN.USB?

— Graham

I, too, am wondering about the best way to provide power to the board and to a device connected to USB1 as host. Here is how I learned to hook up a micro-b breakout to USB1 and also how I intend to provide power to the board. The problem is that there is no measured voltage at USB1:

I was wondering if I could just power the USB1 device from P1_24 SYS VOUT (which does have power when board is supplied by P1_01 SYS VIN) like this:

Would it be harmful to do it this way? Are there better ways to accomplish this? Thanks!

– Will Bain

Your first connection does not work, because you are trying to power the USB1 from the USB_VIN, but since the is no power going into USB_VIN on USB-0, there is no power to come out USB-1.
This only works when the board is powered from USB-0
The schematic does not tell you, but USB_VIN, USB0_VIN and USB1_VIN are all connected together.

VIN is a totally separate power supply input

Since you are powering the board from VIN (P1-01) you need to hook the 5V line on your Micro-USB board to P1-01 and P1-05.

In this case, it will work, although you have no current limit protection from a short on the 5V line in a downstream USB device, which is required by the USB spec.
So, only plug in USB devices and cables you trust.

I would not power the USB-5V-VBUS from the SYS-VOUT, because SYS-VOUT is limited to 0.2 A or so, and many USB devices draw more current than this (USB-2 devices are allowed to draw up to 0.9 A)

— Graham

Graham –

Thanks for the advice! That totally makes sense. I now intend to try this configuration to get the added USB1 working in host mode (e.g., to control a Sony camera using the gphoto2 library):

These USB power switch ICs (e.g., Diodes Incorporated AP2822AKATR-G1, Richtek RT9711CGB, Richtek RT9742JNGV) limit current, prevent reverse current, etc., and cost less than a dollar. I’ll report back about whether this ends up working okay.

– Will

If your USB power switch requires an On/Off enable control input, that is what pin P1-03 is for.
— Graham

Graham –

I figured that’s probably what USB1_EN is for. Most of the USB power switches have an enable pin (the 4- or 5-legged ICs), but a couple of them don’t (the 3-legged ICs). Thanks again for the advice!

– Will

Hello, I am planning to use this setup, Have you successfully implemented and completed tests ?


Works fine. As long as power/Vusb is on Vi (P1-pin 7)
— Graham

I have had it running almost like this (but with just a wire in place of the USB power switch module) for a few hours each day for the last couple weeks or so, and haven’t let the magic blue smoke out of my device yet! I plugged a wi-fi dongle into the added USB jack, and the dongle gets pretty hot to the touch, but it works fine and the heat doesn’t seem to cause any problems. Haven’t tried controlling a camera with it yet.

– Will

OK its working, decided to play safe, so everything is on jumpers :wink:

Hi all,