Power FROM Arduino USB

Hi there, Assuming that I am feeding an Arduino through the power jack... can I use the USB connector to feed USB devices? I would like to be able to charge and talk to a mobile phone (assuming the mobile phone has some custom terminal-like app running). Are any of those things possible?

I have seen there's an USB-host shield, which seems to provide charging and so on, I wonder if it's really needed for what I want :) Thanks! -rod

Charging is possible with a simple socket and four resistors on the data line. To talk to the mobile phone you will need the host shield.

Thanks for your answering so quickly!

I was under that impression. But there's one bit that I don't quite understand... I can talk from a computer using that same USB connection, why shouldn't I be able to talk to a e.g. phone? About those resistors, any place I can get info on that? thanks!

I can talk from a computer using that same USB connection, why shouldn't I be able to talk to a e.g. phone?

An Arduino board is a USB device that works only with a USB host device (such as your PC). Your phone is a USB device that also can talk to only to a USB host device. An arduino to phone connection will not work as neither device is a USB host device.

Lefty

so that would limit things to laptops and desktops and, what about smartphone-level devices (iPhone? iPad? Android?) Also... how much power would I be able to drain from the USB? thanks again! Damn you guys are fast :D

Generally if it is meant to be connected to a computer it is not a host, so no they would not work. USB power is limited to 0.5A.