HID descriptor

[yoshimura]

Hello,

I am using HID mouse/keyboard examples from SDK to learn creating custom HID device.

Besides using four buttons on EVK to simulate motion action. I would love sending zooming in/out actions from custom devices to android devices. I realize I would need to understand HID or generic USB descriptor protocol to create proper descriptor table.

However, after going through multiple online examples, I am still struggling to find a understandable tutorials or specs (e.g.www.usb.org/.../Hut1_12v2.pdf) to create a custom descriptor table based on hardware configuration.

How are the hex values determined? Would it matter to use different type of devices defined in usb spec such as digitizer, mouse, desktop or etc...

Thank you! I really appreciate your input.

[Hung Bui]

Hi Yoshimura,

Would it's possible to map zoom functioning to the volume button on the phone ? Here is one example from my coworker on how to configure HID report as Consumer Control and send the volume keys. Pressing button 3 will send a volume up and button 4 volume down

[yoshimura]

Hi Hung, if I understand correctly, I should be able to remap volume keys action on the phone to emulate zoom in/out actions?

[Hung Bui]

Yes, it's an option. I'm not sure if there is actually a way to send a key to change zoom level besides the volume buttons.

[yoshimura]

Hi Hung, thanks for taking time to answer the questions. The example is really helpful. Wondering what 0x81, 0x02 // Input (Data,Value,Relative,Bit Field) Stands for here. I guess this is more general description table question. After looking up USB HID Usage table, for consumer control devices zoom in/out are mapped to 22D/E/F, so I guess, I can append new fields to the description like this?

[Hung Bui]

Hi Yoshimura-san, 0x81, 0x02 describe the input report, is a data (not constant), variable (not array), relative (not absolute) and is bit field as they are boolean. There is a tutorial here that you can have a look.

Regarding the zoom in/out descriptor you pointed to, I believe it's to zoom in and out on the GUI screen, not to zoom in and out the camera. You need to check with Android.