Android Open Accessory (AOA)

[some1]

Hello, i am tying to use the C2 board as client and connect it to device that supports AOA and acts like a host.
When i connect both devices, host device asks the C2 if it supports AOA protocol and C2 respond that it is support AOAv2,
after that Host device send a command to C2 to enter accessory mode but its not happen.

I tried both versions of Android you provide for C2 and since Android version (AOSP) by default supports AOAv2,
my guess that there is something missing or disabled in the Kernel.

Can you please help me with this or point me in the right direction?

[some1]

Can I get some attention please? any help are welcome...

[odroid]

We have no idea how to enable the AOAv1 in the current Android platform.
Which device do you want to connect to C2?

[some1]

We are working with custom device (Host) that support AOAv2.
Everything works fine and tested on LG, Samsung and AndroidOne (unmodified Android operating system) phones.
C2 board also working fine, until the moment when Host asks him to enter accessory mode and nothing happens.

It looks like C2 just missing something, one think i notice for example:
C2 and manufactured phones both has xml file android.hardware.usb.accessory.xml with next content:

Code: Select all

<!-- This is the standard feature indicating that the device supports USB accessories. -->
<permissions>
    <feature name="android.hardware.usb.accessory" />
    <library name="com.android.future.usb.accessory"
            file="/system/framework/com.android.future.usb.accessory.jar" />
</permissions>

The xml content are exactly the same on C2 and Samsung J5 phone for example, note the jar path:
file="/system/framework/com.android.future.usb.accessory.jar"

Lets find the actual jars paths:

Command:

Code: Select all

adb shell find / -name *accessory* 2>/dev/null | grep accessory

on Odroid C2, give us the next result:

/dev/usb_accessory
/etc/permissions/android.hardware.usb.accessory.xml
/framework/com.android.future.usb.accessory.jar
/framework/oat/arm/com.android.future.usb.accessory.odex
/sys/devices/virtual/misc/usb_accessory
/sys/devices/virtual/android_usb/android0/f_accessory
/sys/class/misc/usb_accessory
/sys/class/android_usb/f_accessory

Command:

Code: Select all

adb shell find / -name *accessory* 2>/dev/null | grep accessory

on Samsung J5, give us the next result:

/system/etc/permissions/android.hardware.usb.accessory.xml
/system/framework/arm/com.android.future.usb.accessory.odex
/system/framework/com.android.future.usb.accessory.jar
/sys/devices/soc0/accessory_chip
/sys/devices/virtual/misc/usb_accessory
/sys/devices/virtual/android_usb/android0/f_accessory
/sys/class/misc/usb_accessory
/sys/class/android_usb/f_accessory
/dev/usb_accessory

There is a couple of difference here, but the most interesting is that accessory jar sitting in different location on Odroid C2,

[rooted]

Try copying it to the missing location

[odroid]

We will check the AOAv2 functionality with our USB IO board on C2 Android 6.x image.
https://wiki.odroid.com/accessory/add-on_boards/usbioboard#example_host_software_source_code_for_android

[codewalker]

I install this app.
https://play.google.com/store/apps/deta ... DeviceDemo

I connect USB IO Board via USB Host port.
https://www.hardkernel.com/main/product ... 5390529643

IMG_20180803_105012.jpg (377.79 KiB) Viewed 693 times

Screenshot_20180803-104251.png (55.71 KiB) Viewed 693 times

Screenshot_20180803-104309.png (44.61 KiB) Viewed 693 times

[some1]

I install this app.
https://play.google.com/store/apps/deta ... DeviceDemo
I connect USB IO Board via USB Host port.
https://www.hardkernel.com/main/product ... 5390529643

IMG_20180803_105012.jpg

Screenshot_20180803-104251.png

Screenshot_20180803-104309.png

Thanks for the work done, but this application does not check operability of the AOAv2/AOAv1 protocols.
Communication through USB works well until the point we want to start communicate via AOAv2 protocol.

[some1]

We will check the AOAv2 functionality with our USB IO board on C2 Android 6.x image.
https://wiki.odroid.com/accessory/add-on_boards/usbioboard#example_host_software_source_code_for_android

Thank you very much, here is the Android promt that notify the user that he is going to connect to accessory (Never seen on Odroid C2).
Note: the promt says USB Accessory not USB Device.
This screen shows what happen on manufactured phones when we connect them to custom device (Host) that support AOAv2.
This screen never appear on Odroid C2.

[odroid]

What is the main difference between V1 and V2?
Our USB IO board was tested by codewalker and it worked in V2 mode correctly.
We don't know how to enable the pop-up since we couldn't find the V1 API in the current Android framework source code.
Did you have a chance to search the Android source code?

[some1]

Difference is in available modes:

AOAv1:
0x2D00 accessory Provides two bulk endpoints for communicating with an Android application.
0x2D01 accessory + adb For debugging purposes during accessory development. Available only if the user has enabled USB Debugging in the Anddroid device settings.
AOAv2:
0x2D02 audio For streaming audio from an Android device to an accessory.
0x2D03 audio + adb
0x2D04 accessory + audio
0x2D05 accessory + audio + adb

https://source.android.com/devices/accessories/aoa2

codewalker user, does not check operability of the AOA protocols,
the usb communication works well until the point we want to start communicate via AOA protocol.

The popup is just a "flag" that it works, and has nothing to do with the version of the protocol,
just like the codewalker user popup that says "USB Device is connected" has nothing to do with the USB version.

The popup asking for user permission to handle the connection, and asks what application should handle the connection,
his absence simply says that no protocol connection is established and there is nothing to ask or notify the user.

Important note: before we start the AOA communication, we communicate via USB "normally" and it works well, we asks Odroid C2 for its protocol version and he respond, so we have USB communication. The problem starts when we asking the C2 to enter accessory mode, C2 should drop existing usb communication and enter accessory mode and establish communication via AOA protocol.

[codewalker]

Hi, some1.
Could you swap jar between j5 and odroid-c2.
I wonder it of the result.

Difference is in available modes:

AOAv1:
0x2D00 accessory Provides two bulk endpoints for communicating with an Android application.
0x2D01 accessory + adb For debugging purposes during accessory development. Available only if the user has enabled USB Debugging in the Anddroid device settings.
AOAv2:
0x2D02 audio For streaming audio from an Android device to an accessory.
0x2D03 audio + adb
0x2D04 accessory + audio
0x2D05 accessory + audio + adb

https://source.android.com/devices/accessories/aoa2

codewalker user, does not check operability of the AOA protocols,
the usb communication works well until the point we want to start communicate via AOA protocol.

The popup is just a "flag" that it works, and has nothing to do with the version of the protocol,
just like the codewalker user popup that says "USB Device is connected" has nothing to do with the USB version.

The popup asking for user permission to handle the connection, and asks what application should handle the connection,
his absence simply says that no protocol connection is established and there is nothing to ask or notify the user.

Important note: before we start the AOA communication, we communicate via USB "normally" and it works well, we asks Odroid C2 for its protocol version and he respond, so we have USB communication. The problem starts when we asking the C2 to enter accessory mode, C2 should drop existing usb communication and enter accessory mode and establish communication via AOA protocol.

[tobetter]

@some1, I think the feature is missing in the current Android C2 release. Please let HK team have some time to review it and get back to you. By the way, what ODROID-C2 supposed to be if it can be switched into device mode with your custom hardware? Like HID or Audio?

[tobetter]

@some1, would you be able to change the file init.odroidc2.usb.rc by adding accessary to every single line?

Code: Select all

diff --git a/init.odroidc2.usb.rc b/init.odroidc2.usb.rc
index 9ad2e4c..916c325 100644
--- a/init.odroidc2.usb.rc
+++ b/init.odroidc2.usb.rc
@@ -15,7 +15,7 @@ on boot
     write /sys/class/android_usb/android0/f_mass_storage/vendor_string ${ro.usb.vendor.string}
     write /sys/class/android_usb/android0/f_mass_storage/product_string ${ro.usb.product.string}
 
-on property:sys.usb.config=mass_storage
+on property:sys.usb.config=mass_storage,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -24,7 +24,7 @@ on property:sys.usb.config=mass_storage
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mass_storage,adb
+on property:sys.usb.config=mass_storage,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -34,7 +34,7 @@ on property:sys.usb.config=mass_storage,adb
     start adbd
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mtp
+on property:sys.usb.config=mtp,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -43,7 +43,7 @@ on property:sys.usb.config=mtp
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mtp,adb
+on property:sys.usb.config=mtp,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -53,7 +53,7 @@ on property:sys.usb.config=mtp,adb
     start adbd
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=ptp
+on property:sys.usb.config=ptp,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -62,7 +62,7 @@ on property:sys.usb.config=ptp
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=ptp,adb
+on property:sys.usb.config=ptp,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1


Also you must change the key persist.sys.usb.config in the file /system/default.prop to have accessory whichever you have currently, such that Android Accessory gadget can be activated in the kernel space. For sure, you must reboot your ODROID-C2.

[some1]

@some1, would you be able to change the file init.odroidc2.usb.rc by adding accessary to every single line?

Code: Select all

diff --git a/init.odroidc2.usb.rc b/init.odroidc2.usb.rc
index 9ad2e4c..916c325 100644
--- a/init.odroidc2.usb.rc
+++ b/init.odroidc2.usb.rc
@@ -15,7 +15,7 @@ on boot
     write /sys/class/android_usb/android0/f_mass_storage/vendor_string ${ro.usb.vendor.string}
     write /sys/class/android_usb/android0/f_mass_storage/product_string ${ro.usb.product.string}
 
-on property:sys.usb.config=mass_storage
+on property:sys.usb.config=mass_storage,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -24,7 +24,7 @@ on property:sys.usb.config=mass_storage
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mass_storage,adb
+on property:sys.usb.config=mass_storage,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -34,7 +34,7 @@ on property:sys.usb.config=mass_storage,adb
     start adbd
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mtp
+on property:sys.usb.config=mtp,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -43,7 +43,7 @@ on property:sys.usb.config=mtp
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mtp,adb
+on property:sys.usb.config=mtp,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -53,7 +53,7 @@ on property:sys.usb.config=mtp,adb
     start adbd
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=ptp
+on property:sys.usb.config=ptp,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -62,7 +62,7 @@ on property:sys.usb.config=ptp
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=ptp,adb
+on property:sys.usb.config=ptp,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1


Also you must change the key persist.sys.usb.config in the file /system/default.prop to have accessory whichever you have currently, such that Android Accessory gadget can be activated in the kernel space. For sure, you must reboot your ODROID-C2.

Hi tobetter. I will definitely try it today and let you know, thank you very much.
For your question, what ODROID-C2 supposed to be, well I develop a concept for the customer, in which one of the features is the AndroidAuto.
You can try it by your self by installing Gapps and AndroidAuto apk on C2 and connect it to a car that supports AndroidAuto.

[some1]

@some1, would you be able to change the file init.odroidc2.usb.rc by adding accessary to every single line?

Code: Select all

diff --git a/init.odroidc2.usb.rc b/init.odroidc2.usb.rc
index 9ad2e4c..916c325 100644
--- a/init.odroidc2.usb.rc
+++ b/init.odroidc2.usb.rc
@@ -15,7 +15,7 @@ on boot
     write /sys/class/android_usb/android0/f_mass_storage/vendor_string ${ro.usb.vendor.string}
     write /sys/class/android_usb/android0/f_mass_storage/product_string ${ro.usb.product.string}
 
-on property:sys.usb.config=mass_storage
+on property:sys.usb.config=mass_storage,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -24,7 +24,7 @@ on property:sys.usb.config=mass_storage
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mass_storage,adb
+on property:sys.usb.config=mass_storage,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -34,7 +34,7 @@ on property:sys.usb.config=mass_storage,adb
     start adbd
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mtp
+on property:sys.usb.config=mtp,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -43,7 +43,7 @@ on property:sys.usb.config=mtp
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=mtp,adb
+on property:sys.usb.config=mtp,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -53,7 +53,7 @@ on property:sys.usb.config=mtp,adb
     start adbd
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=ptp
+on property:sys.usb.config=ptp,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1
@@ -62,7 +62,7 @@ on property:sys.usb.config=ptp
     write /sys/class/android_usb/android0/enable 1
     setprop sys.usb.state ${sys.usb.config}
 
-on property:sys.usb.config=ptp,adb
+on property:sys.usb.config=ptp,adb,accessory
     stop adbd
     write /sys/class/android_usb/android0/enable 0
     write /sys/class/android_usb/android0/idVendor 18d1


Also you must change the key persist.sys.usb.config in the file /system/default.prop to have accessory whichever you have currently, such that Android Accessory gadget can be activated in the kernel space. For sure, you must reboot your ODROID-C2.

Sorry for keep you waiting, it doesn't worked, i also tried to add separate "on property" blocks with correct vendor and product ids for each accessory modes that match Google documentation, nothing.
A quick glance you can tell that everything is in place, there is lots of accessory code inside the droid build, odroid even has /dev/usb_accessory ready and waiting for its moment to shine but something is just missing, something in Kernel config maybe, even there are mentions of accessories, moreover they are included. This protocol getting more and more popularity and possibilities with boards like C2 are huge.

[tobetter]

@some1, sorry to hear that it doesn't help you. Would you please have a little bit of patient for some time?
Let me try more carefully and get back to you.

[some1]

Hi all, I finally got to find the problem which did not allow to C2 to enter the accessory mode.
I had to assemble several android builds from source (Marshmallow) with a thorough debug
and trace what happened when C2 is connected to a host accessory.
Thank for such a good wiki which made this possible.

At the moment I do not know how to solve the problem itself, but I know how to get around it.
I'm sure that you can fix the faulty code, and everything will work well without the workaround.

Method where the code stopped located in UsbDeviceManager.java class (path below).

marshmallow/frameworks/base/services/usb/java/com/android/server/usb/UsbDeviceManager.java

Code: Select all

    private void startAccessoryMode() {
        if (!mHasUsbAccessory) return;

        mAccessoryStrings = nativeGetAccessoryStrings();
        boolean enableAudio = (nativeGetAudioMode() == AUDIO_MODE_SOURCE);
        // don't start accessory mode if our mandatory strings have not been set
        boolean enableAccessory = (mAccessoryStrings != null &&
                        mAccessoryStrings[UsbAccessory.MANUFACTURER_STRING] != null &&
                        mAccessoryStrings[UsbAccessory.MODEL_STRING] != null);
        String functions = null;

        if (enableAccessory && enableAudio) {
            functions = UsbManager.USB_FUNCTION_ACCESSORY + ","
                    + UsbManager.USB_FUNCTION_AUDIO_SOURCE;
        } else if (enableAccessory) {
            functions = UsbManager.USB_FUNCTION_ACCESSORY;
        } else if (enableAudio) {
            functions = UsbManager.USB_FUNCTION_AUDIO_SOURCE;
        }

        if (functions != null) {
            mAccessoryModeRequestTime = SystemClock.elapsedRealtime();
            setCurrentFunctions(functions);
        }
    }

Take a look on method nativeGetAccessoryStrings for some reason always returns an array of nulls.
Because of this enableAccessory boolean is always false and the functions string remains null and setCurrentFunctions method is never called here.

If we set hard coded values to mAccessoryStrings after nativeGetAccessoryStrings call, the code continues to run,
and eventually the applications on the phone will get the accessory connected event and will be able to handle the connection via the protocol.

Code: Select all

    mAccessoryStrings = nativeGetAccessoryStrings();
        mAccessoryStrings[UsbAccessory.MANUFACTURER_STRING] = "Android";
        mAccessoryStrings[UsbAccessory.MODEL_STRING] = "Android";
        mAccessoryStrings[UsbAccessory.VERSION_STRING] = "1.0";

Native methods for this class are located in:

marshmallow/frameworks/base/services/core/jni/com_android_server_UsbDeviceManager.cpp

Code: Select all

    static jobjectArray android_server_UsbDeviceManager_getAccessoryStrings(JNIEnv *env,
                                                                        jobject /* thiz */)
{
    int fd = open(DRIVER_NAME, O_RDWR);
    if (fd < 0) {
        ALOGE("could not open %s", DRIVER_NAME);
        return NULL;
    }
    jclass stringClass = env->FindClass("java/lang/String");
    jobjectArray strArray = env->NewObjectArray(6, stringClass, NULL);
    if (!strArray) goto out;
    set_accessory_string(env, fd, ACCESSORY_GET_STRING_MANUFACTURER, strArray, 0);
    set_accessory_string(env, fd, ACCESSORY_GET_STRING_MODEL, strArray, 1);
    set_accessory_string(env, fd, ACCESSORY_GET_STRING_DESCRIPTION, strArray, 2);
    set_accessory_string(env, fd, ACCESSORY_GET_STRING_VERSION, strArray, 3);
    set_accessory_string(env, fd, ACCESSORY_GET_STRING_URI, strArray, 4);
    set_accessory_string(env, fd, ACCESSORY_GET_STRING_SERIAL, strArray, 5);

out:
    close(fd);
    return strArray;
}

I hope that you will be able to fix the reason why native methods return incorrect values (this native methods communicate with the kernel and the driver).
by the way when you connect C2 to the accessory host sometimes C2 freezes and you need to restart it, I think it's interconnected.