Send output to a device to change channel in a Logitech mouse/keyboard

I have a Logitech mouse and keyboard supporting switching between multiple devices. The feature I am missing is to simultaneously switch mouse and keyboard by running a command or a shortcut.

Is it possible to send output to a mouse and keyboard to change its channel? If so, how can I do that?

I don't have any experience in USB HID, but I used the busdog tool to sniff output, and I found that following code is send every time I press a key to change channel from the first to the second one.

Code:

10 03 41 04 71 8a 40

Afterwards, I tried to use commandline tool called hidapitester to send the code to a keyboard, hoping that it will change its channel. Unfortunately, without a result.

$ hidapitester --vidpid 046D/C52B --list

046D/C52B: Logitech - USB Receiver
046D/C52B: Logitech - USB Receiver
046D/C52B: Logitech - USB Receiver
046D/C52B: Logitech - USB Receiver

Opening device, vid/pid: 0x046D/0xC52B
Closing device


$ hidapitester --vidpid 046D/C52B --open --length 7 --send-output 0x10 0x03 0x41 0x04 0x71 0x8a 0x40 --read-input

Opening device, vid/pid: 0x046D/0xC52B
Writing output report of 7-bytes...wrote -1 bytes:
 10 00 00 00 00 00 00
Reading 7-byte input report 0, 250 msec timeout...read -1 bytes:
Closing device

Below, I am adding the trace log after I press a key switching from the first to the second channel:

Id    Type                        Time        Length    Hex
24    In  (USB URB Function: 9)    0.000000    20        11 03 08 20 00 d2 01 00 00 00 00 00 00 00 00 00 00 00 00 00
29    R                            0.000377    20        11 03 08 20 00 d2 01 00 00 00 00 00 00 00 00 00 00 00 00 00
24    In  (USB URB Function: 9)    0.291648    7        10 03 41 04 71 8a 40
28    R                            0.000449    7        10 03 41 04 71 8a 40

Solution

The codes you captured are the result of switching (not actually the command to switch). You need to use different codes to make it switch, as follows (Credit to @davidschreiber):

10 [device index] 08 10 [channel index] 00 00 00

The first item must be 10
[Device Index] is one-based and depends on the order your devices were registered (so trial and error is needed)
08 and 10 can actually vary in a wide range. I use 09 and 11 and that also seems to work!
[Channel Index] is zero-based and relates directly to 1,2,3 on the keyboard/mouse

Additionally (certainly on windows), you need to specify the usage and usagePage parameters in hidapitester.

So this works for me: Switching my mouse (Device #1 = 0x01) onto Channel 3 (0x02)

hidapitester.exe --vidpid 046D:C52B --usage 1 --usagePage 0xFF00 --open --length 7 --send-output 0x10,0x01,0x09,0x11,0x02,0x00,0x00

You can find loads more amazingly useful information here: Device change button does not affect other connected devices #28