ChromeBook USB API

[jason wu]

Hi, 

    I am using HP ChormeBook and want to try the sample code from here, the usb device_info. 

    but i am stuck on the function "chrome.usb.getDevices", seems like the function can run. 

    but always found 0 devices? I just copy all the files from the sample file. 

Thanks for the help.

    

    

[jason wu]

just passed last step. 

now stuck at 

chrome.usb.requestAccess(..)

this function can pass. but has no effect, 

so the next function chrome.usb.openDevice(...) will always fail. 

on chorme os only. 

why?

[Reilly Grant]

What failure are you seeing? There should be a message in chrome.runtime.lastError.

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[jason wu]

Actually there's no failing message. 

the sample I am trying to run is 

https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/usb/device-info

either function i am trying use to get a device handle is 

1. requestAccess

2. findDevice 

either of them not working? or I require to input instanceId? (does not know how to get this)

but the sample code is working on windows7 base

what i am trying to work out is on my 

HP chormeBook.  

Reilly Grant於 2015年8月13日星期四 UTC+8上午2時00分46秒寫道：

[Reilly Grant]

There is no instanceId parameter in the USB API. I don't know where you got that. Every function will either provide the documented arguments or set chrome.runtime.lastError.

In the sample if opening the device fails the error is displayed. Does opening the device work in the sample?

[jason wu]

Let me try to explain the full story again.

I am trying to send some vendor command to my USB device under Chrome Book.

after doing a bit research, i tried to use the chrome.usb API from here.

https://developer.chrome.com/apps/app_usb

 

and I have found some samples from here.

https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/usb/device-info

 

the sample I have tried, both working on Windows7, and Ubutnu14, but NOT on chrome Book.

which Ubuntu14 need root privilege, normal mode will show "permission is denied." under chrome.runtime.lastError.message

so I reckon, if we can get enough privilege on Chrome Book? we can also access(unlock) the USB device from chrome api.

 

     Failed chrome book sample

Windows can work

Ubuntu can work.

[jason wu]

Forget to mentioned the code.

I fail at trying to open USB handle.

Doesn’t matter I am using either one, they failed

 

chrome.usb.openDevice(device, function(handle)

chrome.usb.findDevices({"vendorId": device.vendorId, "productId": device.productId}, function(handles)

 

chrome.usb.openDevice says “permission is denied”

and

chrome.usb.findDevices not return fail message, but the handles it has return, has 0 length.

Means nothing device is found. 

jason wu於 2015年8月14日星期五 UTC+8下午2時41分38秒寫道：

[Reilly Grant]

From the screenshot on Windows it looks like the device is an audio device. This means that Chrome OS has a kernel driver loaded for the device. Devices with kernel drivers cannot be opened by the USB API on Chrome OS unless there is an interface that is not claimed by the kernel. Why are you trying to open the device with the USB API instead of using the getUserMedia API to playback or record audio from the device?

--

[jason wu]

Thanks for reply Reilly. 

That was a Genesys Hub device I am trying to open, the audio is just a sample. sorry for the confusion. 

what I am trying to do is to send some vendor command to the Genesys Hub. 

but at first we need to at least open the USB device. now the problem is the device cannot be open on ChromeOS. 

[Reilly Grant]

For this to work the hub must implement these commands on a separate interface from the standard USB hub class implementation. This is done for system security, we don't want Chrome Apps interfering with existing kernel drivers.

[jason wu]

ok understand. 

Is there any sample i can find to implement those commands on separate interface?

so I can either. 

1. modify kernel driver to execute my genesys hub command on start up. 

2. do some special hub interface (need your help to tell me where is the sample ).

Thanks a lot for help!

[Reilly Grant]

For 1, I suggest working on getting support for the command into the Linux kernel.

For 2, do you work for Genesys and have the ability to modify their hub firmware? Otherwise there's no hope of modifying the interfaces it provides.

--

[jason wu]

Yes I work for Genesys Logic, we could modify the hub firmware, 

i am thinking to trigger a vendor command to turn some effect on/off with 

chrome.usb.xxxx 

Reilly Grant於 2015年8月20日星期四 UTC+8上午1時37分27秒寫道：

[Reilly Grant]

For this to work the device must be a composite device with two interfaces, one the standard hub interface and one for your effects. I don't know if hubs are allowed by the specification to be composite devices, so you may have to move the effect functionality into a separate device that is connected to the hub internally. I've seen examples of this (in USB Bluetooth controllers) where the device connection is actually virtual, no real hub port is used, but it allows the hub to have extra functionality not allowed by the specification.