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):
<https://lh3.googleusercontent.com/-lu0aOUP8tbc/Wg8Z3vezBxI/AAAAAAAAAUQ/ud2QXK4zW9gwIhrqVif5ChtTqCcqjDicQCLcBGAs/s1600/PocketBeagle_microUSB_3.png> 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 On Thursday, November 16, 2017 at 5:10:48 PM UTC-7, Graham wrote: > > 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 > > == > > On Thursday, November 16, 2017 at 5:11:52 PM UTC-6, [email protected] > wrote: >> >> 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: >> >> >> <https://lh3.googleusercontent.com/-XyHjxbobnnY/Wg3xGzyvNcI/AAAAAAAAATo/u1ufBwtum9c4KA6T6zjnu38x4cwwQ3TNQCLcBGAs/s1600/PocketBeagle_microUSB_1.png> >> >> 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: >> >> >> <https://lh3.googleusercontent.com/-l4RYr7WmaGU/Wg3xqYECajI/AAAAAAAAATw/ipK3CZmhG18cieC-bnMLV04PfPBl_hRRACLcBGAs/s1600/PocketBeagle_microUSB_2.png> >> Would it be harmful to do it this way? Are there better ways to >> accomplish this? Thanks! >> >> -- Will Bain >> >> >> On Sunday, November 5, 2017 at 6:59:39 PM UTC-7, Graham wrote: >>> >>> 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 >>> >>> == >>> >>> On Sunday, November 5, 2017 at 6:58:06 PM UTC-6, Graham wrote: >>>> >>>> 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 >>>> >>>> == >>>> >>> -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/56d1aec9-9887-4f20-a98e-21c56fcd2cf5%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
