Lime2 defect?

[pvdv]

Hello,

I have a Lime2 and I think it's defect, but I am not sure.

First I have tried to connect the USB-OTG connector to a USB connector of a PC without a SD card.
I don't see any LED's blinking on the Lime2.

Second test is putting an SD-card with Debian Jessie and connect the Lime2 to a HDMI monitor and to a USB keyboard. Again power with USB-OTG to a computer.
I don't see LED's on the lime2 or on the keyboard. And no signal on the monitor.

Is this Lime2 defect?

With regards,
Paul van der Vlis.

[Gerrit]

Use a good 5V power supply on the power connector, I never got it working powering through the USB-OTG connector

[soenke]

Some USB-ports dont deliver enough power to supply the A20. But there are some ports which have more than 5W, e.g. "power-ports" on some laptops. It might help to try another USB-port, plug off some other USB-devices or use an external USB-hub with external power supply if you have one.
But the best power supply for the A20 is still a good separate 5V-adapter.

[jmyreen]

Some USB-ports dont deliver enough power to supply the A20.

The problem is not so much how much power a USB port can deliver, but how much power the consumer is allowed to draw. The USB spec defines an intelligent power budget scheme, to prevent a single device to bring the whole system down by drawing too much current. When plugged in, a USB device playing strictly by the rules isn't allowed to draw more than 100 mA, but it can ask the host for more. The host can then either accept or deny the request, depending on what the total load on the bus is.

Recent revisions of the USB specs include a "Battery Charging Spec", targeting dumb USB chargers. These chargers short the data lines, which the device interprets that it is connected to a charger which can deliver a lot of power. But it is still the responsibility of the device to detect this condition and act accordingly.

See this post for a description of how the Lime2 handles all this (TL;DR: the current is limited to 900 mA):

https://www.olimex.com/forum/index.php?topic=4058.msg17333#msg17333

[pvdv]

Use a good 5V power supply on the power connector, I never got it working powering through the USB-OTG connector

Thanks for your help, that's interesting information. I've tried it with an USB-adapter with 3.1A max, and on two other ones (a USB3 port and an powered USB2 hub).

With regards,
Paul van der Vlis

[pvdv]

Use a good 5V power supply on the power connector, I never got it working powering through the USB-OTG connector

It works now with the 5V power supply and the Debian image from Olimex. Thanks for your help.

I also got an answer from support, they told me there is no power LED when you use the miniUSB port.

With regards,
Paul van der Vlis.