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#USB RECIVER LOGITECH WIRELESS SOLAR KEYBOARD K750 HOW TO#
#USB RECIVER LOGITECH WIRELESS SOLAR KEYBOARD K750 DRIVER#
#USB RECIVER LOGITECH WIRELESS SOLAR KEYBOARD K750 CODE#
#USB RECIVER LOGITECH WIRELESS SOLAR KEYBOARD K750 WINDOWS#

With all this, the next step was clear: understand the packets and reproduce that exchange under Linux.

Regularly URB interrupt packets are sent just after.

An URB control packet is sent by the computer to the keyboard in response.

When pressing the "light" button, an URB of type interrupt is sent by the keyboard to the computer.

Here's the interesting packets that I noticed once I excluded the noise: Pressing the "light" button on the keyboard makes even more USB packets coming in and out. Therefore I advise you to plug another keyboard (or use the laptop keyboard if you're doing this on a laptop), otherwise you'll get crazy trying to sniff the keyboard you're typing on.Īt this point, just launching the application does a bunch of USB traffic. There's a an URB of type interrupt sent each time you press any key with some data in it. Once everything was set-up, I ran my beloved Wireshark.

Controls packets, used for command and status operations.Īll of this and more is well (and better) explained in the chapter 13 of Linux Device Drivers, Third Edition.

Interrupt packets, a packet send spontaneously.

There's also several types of packets in the USB wire protocol, and at least two of them interest us there, they are: A device might contains one or several configurations. Interfaces are regrouped into a configuration. Endpoints are regrouped into an interface. To communicate with an USB device, we communicate with one of its endpoints. You don't need to know much about USB to understand what I'll write about below, but for the sake of comprehensibility I'll write a couple of things here before jumping in.

#USB RECIVER LOGITECH WIRELESS SOLAR KEYBOARD K750 HOW TO#

You can then use Wireshark which know how to use usbmon devices and understand the USB protocol. To sniff what happens on the USB, you need to load the usbmon Linux kernel module. Both KVM and VirtualBox can do that, but VirtualBox works much better with USB and allow hot(un)plugging of devices, so I used it. To achieve that, you need a virtual machine emulator that can do USB pass-through. I did not need it, but I learned a few things.Īnyway, my plan was the following: run the Logitech application inside a virtual machine running Windows, give it direct access to the USB keyboard, and sniff what happens on the USB wire. You might want to take a look at it if you want to reverse engineer on USB. I discovered a bit too late that Drew Fisher did a good presentation on USB reverse engineering at 28c3. So the first task to accomplish is, unfortunately, to reverse engineer the program. Let's reverse engineer thisĪs far as I know, there's nothing in the USB HID protocol that handles this kind of functionality (battery status, light meter…) in a standard way. Pushing this same button while the application is running will makes the light meter activated: the application will tell you how much lux your keyboard is receiving. When pressed, a LED will light up on the keyboard: green if the keyboard is receiving enough light and is charging, red if the keyboard does not receive enough light and is therefore discharging. On the keyboard, there's a special "light" button (up right).

#USB RECIVER LOGITECH WIRELESS SOLAR KEYBOARD K750 WINDOWS#

The Logitech application under Windows works that way: you launch it, and it displays the battery charge level. With this driver, each device attached to the receiver is recognized as one different device.

#USB RECIVER LOGITECH WIRELESS SOLAR KEYBOARD K750 DRIVER#

Recently, a driver called hid-logitech-dj has been added to the Linux kernel. On old Linux kernel, the Unifying receiver is recognized as only one keyboard and/or one mouse device. It's an USB receiver that can be attached up to 6 differents devices (mouse, keyboards…). This keyboard, like many of the new wireless devices from Logitech, uses the Unifying interface.

#USB RECIVER LOGITECH WIRELESS SOLAR KEYBOARD K750 CODE#

Someone should write code to get the battery status and light meter from Linux: challenge accepted! How the keyboard works

This activity being quite energy consuming, it emptied the whole battery. My problem is that there's obviously no way to know the battery status from Linux, the provided application only working on Windows.Īnd one dark night, while fragging on QuakeLive, my keyboard stopped working: it had no battery left. It has an incredible useful feature: while being wireless, it has no need for disposable or rechargeable batteries, it uses solar power! I'm particularly picky on keyboards, but this one is good. A year ago, I bought a Logitech Wireless Solar Keyboard K750.