Android & Usb Host Shield (or board)

Using Arduino Project Guidance
1

Hi guys,

I'm working on a project where I have to use an Arduino board with an Android tablet.

Both have to communicate with each others using USB serial connection.

I'm looking for an installation that allow the Arduino board to supply power to the tablet and make the two communicate together.

I know that I have to use host mode in the Arduino and Accessory mode in Android, and my tablet support both modes (2012 Nexus 7).

I googled that but i'm not very sure of what i've found.

Can anyone of you assure me that I can do it with an Arduino Uno + Usb host shield or does I have to use Arduino Mega Adk for that ?

Cheers,

Alexandre

2

Yes, you can connect UNO and android via shield. The problem I had, is that arduino can't supply enough current, so whenever my tablet see usb connected its try to switch in charging mode and demand 2 A or so ( tablet's own power supply rated 2 A ). And if usb voltage goes down below 4.4V usb interrupted. I was able to solve issue only by soldering separate +5V power plug on the USB shield, in prototyping area, and connecting external source.

3

Thanks for the answer !

Do you know if this problem happens only with the Uno and Usb Host Shield, or does it happen also with the Mega ADK ?

4

You are welcome.
Can't say about ADK, but web page - docs.cc
says:

NB: Because the MEGA ADK is a USB Host, the phone will attempt to draw power from it when it needs to charge. When the ADK is powered over USB, 500mA total is available for the phone and board.The external power regulator can supply up to 1500mA. 750mA is available for the phone and MEGA ADK board. An additional 750mA is allocated for any actuators and sensors attached to the board. A power supply must be capable of providing 1.5A to use this much current.

Moreover, fuse F2 on electrical drawings for phone USB connector is only 500 mA, so my feeling that would make same troubles.
It looks like, design was made for small android devices, 4.3' or less. As bigger screen more demanding for current, 7' and especially 9'-10' - devices are not gonna be compatible.