Robert, If you have a look at the Pocketbeagle schematic, you can see what happens with the USB connector, which comes in on page 2. Power on that pin goes to VIN.USB, which goes straight to (page 3) the Octavo OSD3358 VIN_USB pins.
You can look at the Octavo datasheet [1] - it's for the OSD335x_SM - they tell you almost nothing. The only partly useful thing they tell you is "The OSD335x-SM may be powered by any combination of the following input power supplies. Please refer to the TPS65217C datasheet for details." The smartest thing to do would be to map the pins to the chips they are connected to using Octavo's tool [2] and the TI datasheets. I'm certain there's no isolation, but there is a switch to enable one or the other inputs (perhaps you had a looser definition of isolation in mind). Figure 11 on page 27 of the TPS65217C datasheet [3] should show you what that looks like. These are configured by the PPATH register in [3], which I am not precisely certain how it is configured in the first place, but you should be able to modify it on I2C0 (I think). All that said, it looks to me like it's fine to do. But I feel like I've done this and had some weird results, I just can't remember exactly what they were. I think the results included unplanned reverse power flow (USB charging other things connected to the same VIN power supply), the device not shutting down exactly as I expected, and similar behavior. I don't think we smoked anything, though, so there's that. Worth looking through that data sheet a little to make sure you're happy first. I would be quite interested to know precisely where PPATH is configured, beyond its default settings. It may be in the uboot source which is not [I think] in the BB distributions. That stuff isn't bad to look at, and I was going to, but for the life of me I can't remember where I built that and I can't find it right now. Robert also has a few scripts in /opt/scripts/boot which configure a LOT of things, I've only scratched the surface trying to understand them. [0] - https://github.com/beagleboard/pocketbeagle/blob/master/PocketBeagle_sch.pdf [1] - https://octavosystems.com/docs/osd335x-sm-datasheet/ [2] - https://octavosystems.com/app_notes/osd335x-family-pin-assignments/ (search for VIN_USB) [3] - http://www.ti.com/lit/ds/symlink/tps65217.pdf Hope that helps. I have nothing to do with the pocket beagle but I did spin a couple boards based on it and the octavo RED board. Best, Jim On Fri, Aug 9, 2019 at 3:33 PM Robert Heller <[email protected]> wrote: > If I am applying a 5V power supply to the Vin pin (P1-1) of a Pocket Beagle > (say from an expansion board that includes a power supply), is it safe to > also > plug in a [powered] micro-USB cable? That is, does the Pocket Beagle have a > power protection / isolation circuit? > > -- > Robert Heller -- 978-544-6933 > Deepwoods Software -- Custom Software Services > http://www.deepsoft.com/ -- Linux Administration Services > [email protected] -- Webhosting Services > > > -- > 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/20190809193224.14FD526C0099%40sharky3.deepsoft.com > . > -- 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/CAGS%2B2h_2WmdGMT8bYPPthv-QMsRSe7QtSP0Xk6_BR_puehw%2B1A%40mail.gmail.com.
