USB_OTG charging current

[adinu]

Hello everybody,

I have a 3000 mAh battery to power the board and I want to be able to charge it through USB_OTG using a power bank like the omega ompb10 (basically an external battery). The one I have is 10000 mAh and has a 5V/2.1A output so it should work, but it doesn't. The device sais charging but the battery percentage actually goes down at a slower pace than it normally would (when only powered by the 3000 mAh bat). It goes down to 0% and the board stays on. I've never waited long enough to see if the board shuts down before the power bank runs out of juice or if it runs with 0% to the end.

Is there a limit to the USB_OTG input current? It sure looks like there is, since the power bank can give up to 2.1A. Does anyone know if that limit can be changed? I've tried touching all the pmu_ parameters in the sys_config.fex file but it makes no difference, I suspect it has nothing to do with the USB_OTG.

I'd love to hear from someone that has encountered this same problem.

Thanks!

[adinu]

In the schematics I found the SY6280 IC which is a current limiter. I'm not sure if it limits the input current or the output current or both (most likely both I would say). In any case, it is set for 523mA. The 12V power supply adapter has 0.5A nominal current and is perfectly capable of powering the board and (slowly) charging the battery.

I measured the current consumption of the board with all the peripherals while powered through the barrel connector and it's about 0.55 - 0.57 A. I suspect the power supply can give that current, plus a small charging current for the battery because it is not limited to it's nominal power, although it should heat up pretty good. On the other hand, because of the SY6280 limiter, the maximum current that can pass through the USB_OTG is 0.523 A.

The limit for the SY6280 can be set by changing the value of a resistor (R45 on the OLiniXino A20). I wonder if we can up that limit with no danger of damaging anything. I sent an e-mail to support@olimex.com. I will update this tread once a get some results

[LubOlimex]

Hello Adrian,

1) SY6280 limits only the output.

2) No need to change anything. Do not remove resistors and such. Just provide power to the OTG connector. It might be able to take up to 2A of current I believe.

You can check the latest schematics available (revision F) – you would see how the other SY6280 are configured differently so one of the USB ports is able to provide up to 1000mA of current.

Best regards and good luck,
Lub/OLIMEXe.

[adinu]

Hi LubOlimex,

The problem is that I cannot power the board with a 10'' screen through OTG connector. The screen doesn't show an image, it just goes on and off. Maybe the board alone can be powered through OTG, I don't know. And there is no way for me to measure the current through that connector, because if I only connect the PWR and GND signals, it doesn't charge. I'm guessing it's because it needs to detect an actual USB device. So I don't know if it's reaching the 2A limit or not.
If I connect a battery, then it will work and the device says it's charging, but it's obviously not charging because it wouldn't make any sense. Like I said before, the battery slowly discharges until it reaches 0% and the device keeps running with 0% anyway.

I just wanted to know if there is a way to correctly supply power to everything through OTG but I'm starting to think there just isn't.

Has anyone managed to power the board + screen through OTG?

Thanks.