My understanding is that the OTG (micro) USB port on the a2109 can't currently be used for charging while it's being used in host mode. (That is, to host peripherals with a host cable, as opposed to plugging the a2109 into a host PC as a peripheral.) BUT some Tegra 3-based machines (Nexus 7?) CAN charge in host mode, with a kind of Y cable (a "host mode cable with power") that you plug into a power supply, if you have an appropriate kernel. (Host mode charging is standardized in the OTG spec, but I don't know if all OTG hardware supports it... maybe it does on other SOC's with OTG, too.) My guess would be that the a2109 could charge in host mode, too, if the appropriate code was included in the kernel; I don't know of any special hardware requirements, and my impression is that it's a matter of the kernel taking proper advantage of the Tegra 3 OTG circuitry that's already there. That would be VERY cool, allowing the OTG USB port plus the HDMI out to be used as a docking port, without depending on any proprietary connectors. IMO the biggest weakness of the a2109 is that it doesn't have a docking solution, and being able to dock it with non-proprietary connectors would be a big strength. Does anybody know if things are headed that way, e.g., the right OTG code being incorporated into the kernel for all Tegra 3 machines? Are such kernels available now for rooted machines? Thanks in advance for any info.