Develop Reference

Android USB Host API - how can I achieve native USB speeds?

I am trying to use the Android USB Host API in order to achieve native USB speeds (on the order of Mbps). I've seen some examples online that use some constants to set up baud rates of 9600. However, I would like to use bulk transfers and control transfers (as necessary, I'm not really sure about how these work, and which constants to use) in order to achieve native USB speeds. Is there any way to do this, and if so, does anyone have some sample code that they would be willing to share? Thanks!
Note: I've also rooted my Android Nexus 7 tablet just in case. I figured that since apps like StickMount need root access, root might be necessary to achieve native USB speeds.

Android sdcard communication through spi

I need to communicate with an modified sdcard in an android phone on very basic level just few commands and responses back. Originally the communication was handled through file system, but when android 4.4 denied access to most of the sdcard this has to be done through SPI, which I hope will work. I have a experience with Android, but not so much in SPI. Could anyone provide a brief tutorial on how to tackle this, or point me to some resources, I couldn't find anything that would deal with how to communicate with sdcard in Android.
Thanks

Direct access to the physical storage device is not permitted on a secured device, as it would be an obvious end-run around the restrictions that are now part of the security model.
On an unsecured (engineering, root hacked, etc) device, if you get a helper executable running as root, you can probably interact with the file system or raw block device just as you were before android 4.4, possibly after shutting down any official-Android components that were talking to it.
Even on an unsecured device, you would need hard-to-obtain SOC-specific peripheral-register programming information to talk to the card in SPI mode (or perhaps by bit-banging the pins in GPIO mode) rather than by the faster 4-bit protocol it is almost certainly using.
If you want a workaround supported by a secured device, then if that device supports USB host mode, you can get an adapter cable and a USB SD reader and talk raw mass storage commands using the Android USB Host APIs. Or if USB mass storage does not give you sufficiently fine-grained control, you can use the SPI mode of an FTDI USB-serial chip, or make something custom with a USB-enabled microconctroller.

Using Android phone as USB Host to mount external drives to phone and accessing the memory of the external drive through phone

I have been checking since some time to mount external drives to android phone i.e., if I plug external drive(hard/flash/camera) to android device, the android phone should be able to access the storage file system.
There are apps in the market which controls external devices through phone.
I can use the USB Host mode { http://developer.android.com/guide/topics/connectivity/usb/index.html } to communicate with the usb device. But USB Host and Accessory modes are directly supported in Android 3.1 (API level 12) or newer platforms.
While an app named DSLR Controller { https://play.google.com/store/apps/details?id=eu.chainfire.dslrcontroller&hl=en } , requires Android 2.1 or above. Since the application is based on accessing the camera through android phone. If the app displays the correct info, then the task of accessing the storage of camera (or any other drive) seems to be possible.
But I want to use the application in lower version as well. Any kind of help will be appreciated.
Please comment,if need any more description of the problem.
Thanks.

You can create an application based on FileManager open source project on Github. You can specify there to identify your device. You can change these code according to your need.
Here is the link Adroid-File-Manager

If you just want to be able to access USB storage (like a flash drive) you can open the files the normal Java way (java.io.File, etc). Android ICS automatically mounts flash drives under /sdcard/usbStorage/, but I'm not sure about previous versions or other types of hardware. It might still work, though, so I'd suggest that you test it and see what happens.

The only sure way of getting this done is to use API level above 12, otherwise a few phones may have support for usb host but most of them wont support it.
The reason being first of all you need hardware support for usb host, even if that is present the drivers needed might not be compiled into the kernel, i did some work while trying to implement usb host on nook color, even though it had hardware support, getting usb host working took almost 2 months and a dedicated app. So its not something you will be able to do for every device. A few might support it out of the box but even those would need root and lots more work for mounting drives and all that..
the DSLR camera also does it the same way look at the requirements
- Android device with ARMv7-A or newer CPU architecture (most 1ghz+ devices)
- Not rooted: Android 3.1 or higher with USB host kernel+API support
- Rooted: Android 2.3.1 or higher with USB host kernel support
These are the only devices that can support USB host.

From the app description, Android 2.x devices need to be rooted. This suggests that they have some native implementation of the USB host code (possibly a pre-compiled kernel module they load).
Therefore, the solution for this varies based on the specific hardware and software (kernel, vendor modifications, skin) it is running.

Android USB isochronous data transfer

I am currently trying to find a way to handle USB data transfer on an isochronous endpoint on my Android 3.2 tablet (Host Mode supported). After writing some prototype code, I noticed that in the constants file for USB_ENDPOINT_XFER_ISOC states that "Isochronous endpoint type (currently not supported)".
Is this possible without rooting the device? If so how would I go about doing this?
Ideally I was hoping to stay within the java API, but if this is possible only via the NDK I would have to pursue that instead. I also understand that there might be some USB bandwidth issues based on the following post: User mode USB isochronous transfer from device-to-host

I have written a Java class for USB isochronous data transfer under Android (or Linux): UsbIso
It uses JNA to access the USBFS API via IOCTL calls.

You "can" do it without root, I believe.
You'll need to do it all using some native C code interfacing with the USB device using USBFS. The big issue comes from the lack of documentation of linux's usbfs. Basically everything has to be done through ioctls. That said you do open a device as you would normally from Java. Then you pass the file descriptor from the USBDeviceConnection
Add to that you will need to parse all the USB descriptors yourself. You can get at them, again from the USBDeviceConnection. Jumping from descriptor to descriptor is simple finding the documentation for what each descriptor means is a MASSIVE headache but you can find most of the documentation on www.usb.org.
I've written most of the code that is required to do the parsing for audio devices and I got all the way up to trying to submit an isochronous transfer and then started getting errors.
After switching to libusb I discovered that the problem, in my case, was because the audio device also had HID controllers and the default driver was atatching to those and stealing all the bandwidth away from the isochronous transfer. Had I known this earlier I might have persevered with the non-root non-libusb method. As it was I did get isochronous transfers working through lib usb but it required a rooted device :(
At some point I'll go back to it.
In summary, I'm pretty sure its possible but its not gonna be easy!!

you can find a runnable Solution of the UsbIso 64 bit on my git hub repo:
https://github.com/Peter-St/Android-UVC-Camera/tree/master/app/src/main/java/humer/uvc_camera/UsbIso64
You need all 5 files of the UsbIso64 folder and can use the USBIso like following:
USBIso usbIso64 = new USBIso(camDeviceConnection.getFileDescriptor(), packetsPerRequest, maxPacketSize, (byte) camStreamingEndpoint.getAddress());
usbIso64.preallocateRequests(activeUrbs);
usbdevice_fs_util.setInterface(camDeviceConnection.getFileDescriptor(), camStreamingInterface.getId(), altSetting);
usbIso64.submitUrbs();
// While loop //
USBIso.Request req = usbIso64.reapRequest(true);
req.initialize();
req.submit();
You can use this version of UsbIso with 32 and 64 bit devices.
So far,
Peter

Embedded System USB to Android Device

I am writing an Android 2.1 application that needs to get data from a USB device. The USB device is an embedded system i created. The embedded system has no OS. Also, the android device does not send any data to the embedded system.
How should i go about this, I'm guessing i will need to make a high-level driver to communicate from USB to the application. But, i have never made a Linux driver before.
If creating a high-level driver is the best way to do this, can someone give me some references so i have somewhere to start.
If there are other ways to accomplish this i would also like to hear about it
-Thanks

The Android Open Accessory Development Kit is where you should start looking. Like many of other Google's documents, the tutorial is reasonably complete and should provide you with a good starting point
Good Luck!

I think you will need to recompile Android kernel to add usb device support.
It can be an option if you are working on some dedicated project and only one Android phone should be supported. If you want to support all kinds of Android phones, I can suggest to implement USB host in your embedded system( if it is possible), thus your Android phone can be connected using ADB protocol.