B4A Library UsbSerial library 2.0 - supports more devices

Creideiki said:

I need the possibility to use ASyncStreams; felUsbSerial doesn't seem to use them.

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Creideiki said:

Is there a HowTo, how to make a B4A-library from java source code?

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slugger said:

Basically there is a foreground service which reads and writes from/to the USB to RS232 adapter and everything works Ok even when the screen turns off.

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agraham said:

This is an expanded version of the original UsbSerial library. It has added support for Prolific PL2303 USB to serial converters, Android ADK devices and USB permissions. All devices use the same simple interface intended to be used with AsyncStreams and AsyncStreamsText. Note that AsyncStreams prefix mode is not supported. The library is based on the same open source project Android USB host serial driver library as the existing UsbSerial library but no longer needs a separate jar file as the project source code is incorporated in the library.

The specific enhancements to the library over the original UsbSerial library are :

UsbPresent, HasPermission and RequestPermission are added to identify any attached device or Accessory available to the library and deal with permission to access it.

SetParameters, which must be used after Open(), and the constants for SetParameters provides acess to all the serial line parameters instead of just baud rate.

DeviceInfo provides a string containing information about a device. This works for slave devices only.

Android Accessories, which are host mode devices, are recognised and can be used in the same way as the other slave mode devices.

Prolific PL2303 support is added.

Silicon Labs CP210x support is added - maybe only the CP2102 as I have no hardware to test.

The FTDI "status byte" bug on reading input that existed in version 1.0 of this library is hopefully fixed.


The usb-serial-for-android project and therefore also this library is licensed under the GNU Lesser General Public License v3. http://www.gnu.org/licenses/lgpl.html|http://www.gnu.org/licenses/lgpl.html
Copies of both the General Public License and Lesser General Public License are in the provided archive.

The user has to give your application permission to access the USB device before it can be opened. You can do this in two ways.

As with the original UsbSerial library you can add the following code to the manifest editor

B4X:

AddActivityText(main, <intent-filter>
        <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
    </intent-filter>
    <meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
        android:resource="@xml/device_filter" />)

Then copy device_filter.xml from the demo in the attached archive to: <your project>\objects\res\xml and mark it as read-only. Note that this is an expanded version of the original device_filter.xml file.

Finally install the program and attach the USB device. A dialog will appear asking whether you want to start your program. If you check the “Use by default…” checkbox from now on when the USB device is plugged in your program will be started. If you don’t check the checkbox then you will be asked each time the device is plugged in.

A similar procedure can be used for Accessories as detailed in the “Using an intent filter” section here USB Accessory | Android Developers


Alternatively you can use the new HasPermission and RequestPermission methods without requiring any of the above steps. The demo in the archive incorporates both ways of obtaining permission.

EDIT:- Version 2.1 now posted. See post #4 for details

EDIT:- Version 2.2 now posted. See post #14 for details

EDIT:- Version 2.3 now posted. See post #26 for details

V2.4 is available here: http://www.b4x.com/android/forum/th...pports-more-devices.28176/page-11#post-259167
This update adds support for devices connected to multiple USB adapters.

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GaNdAlF89 said:

Hi to all! I have an usb barcode reader but it is not detected from this library (usbReader.UsbPresent(1) is equal to usbReader.USB_NONE). I think the problem is that the device is like a keyboard (it needs the focus on an editText).
How can I solve the problem? Or, if the problem is the model of my usb barcode reader, how can I find a device to work correctly with this library? I need asynchronous reading. Thanks!

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GaNdAlF89 said:

Hi to all! I have an usb barcode reader but it is not detected from this library (usbReader.UsbPresent(1) is equal to usbReader.USB_NONE). I think the problem is that the device is like a keyboard (it needs the focus on an editText).
How can I solve the problem? Or, if the problem is the model of my usb barcode reader, how can I find a device to work correctly with this library? I need asynchronous reading. Thanks!

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krokiz said:

I am in need to acquire a continuous stream of byte data from an Serial Device (that I made myself, although AVR MCU based,
Using a FTDI chip in between the Android Tablet and the Device)
The application should continuously receive bytes in range 0x00 to 0xF9, 0xFA is acting as a EOL mark, and draw graphics according to this data.
The issue is the following:
Since the device is sending bytes (data) continuously and might have been turned on prior the connecting to the Tablet,
after the App connects to the external device (by plugging in the micro-B USB cable), The program (UsbSerialDemo) starts, I use the Start Button, the Stop and Send buttons become enabled and then it all goes immediately to the astreams_Error subroutine and displays the following error message:
(IOException) java.io.IOException: Expected at least 2 bytes
My question is: is there a workaround in order to solve this problem and achieve my goal:
Reading the Serial data without ending up in this exception (only) indicating Subroutine (AStreams_Error) ?
(Since I am a newbie in Android and BasicForAndroid, my wildguess is that AsyncStreams are using UTF8 and it expects 2 bytes for each character/byte (of the stream received)

There is an aside question: How could one ignore/process such an exception, since Try..Catch..End Try does not apply here (the exception raises for its reasons, and I cannot trap it) ?


I hope someone could help me out (pray)

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