Commentary

Android Open Accessories

Android’s USB port has in the past been curiously inaccessible to programmers. Last week at Google I/O we announced the Android Open Accessory APIs for Android. These APIs allow USB accessories to connect to Android devices running Android 3.1 or Android 2.3.4 without special licensing or fees. The new “accessory mode” does not require the Android device to support USB Host mode. This post will concentrate on accessory mode, but we also announced USB Host mode APIs for devices with hardware capable of supporting it.

To understand why having a USB port is not sufficient to support accessories let’s quickly look at how USB works. USB is an asymmetric protocol in that one participant acts as a USB Host and all other participants are USB Devices.

In the PC world, a laptop or desktop acts as Host and your printer, mouse, webcam, etc., is the USB Device. The USB Host has two important tasks. The first is to be the bus master and control which device sends data at what times. The second key task is to provide power, since USB is a powered bus.

The problem with supporting accessories on Android in the traditional way is that relatively few devices support Host mode. Android’s answer is to turn the normal USB relationship on its head. In accessory mode the Android phone or tablet acts as the USB Device and the accessory acts as the USB Host. This means that the accessory is the bus master and provides power.

Establishing the Connection Continue reading…

Related Posts

Social Media and Law Enforcement: Who Gets What Data and When? This month, we were reminded how important it is that social media companies do what they can to protect the sensitive data they hold from the pryin...
Why security standards are Critical for the Cloud Everyone loves standards, right? When is the last time you heard a vendor proudly say that their product or service was closed and proprietary? Howe...
Some File-Sharers Leave Trails To Their Front Door Following the publication of a paper which investigates how using the same username across multiple web sites may expose Internet users to scammers, T...
Open Source community building: a guide to getting it right Community development in open source software is not just for geeks in sandals nor for niche Linux companies any more. It’s mainstream and it’s here...
The Open Source trials: hanging in the legal balance of copyright and copyleft For those meddling in open source software affairs, compliance with licenses is a very hot topic. In the last 2 years we have witnessed the licensing ...
An Introduction to the Federated Social Network Lately, EFF's work to protect rights and liberties in the online world has focused rather heavily on social networking sites and their policies. The...

We Recommend These Vendors and Free Offers

Launch an SSD VPS in Europe, USA, Asia & Australia on Vultr's KVM-based Cloud platform starting at $5:00/month (15 GB SSD, 768 MB of RAM).

Deploy an SSD Cloud server in 55 seconds on DigitalOcean. Built for developers and starting at $5:00/month (20 GB SSD, 512 MB of RAM).

Want to become an expert ethical hacker and penetration tester? Request your free video training course of Online Penetration Testing and Ethical Hacking

Whether you're new to Linux or are a Linux guru, you can learn a lot more about the Linux kernel by requesting your free ebook of Linux Kernel In A Nutshell.


Leave a Comment

Your email address will not be published. Required fields are marked *

*