--- title: Solaar Capabilities layout: page --- # Solaar capabilities [**Solaar**][solaar] reports on and controls [Logitech][logitech] devices (keyboards, mice, and trackballs) that connect to your computer via a Logitech USB receiver (a very small piece of hardware that plugs into one of your USB ports) and communicate with the receiver using Logitech's HID++ protocol. Solaar is designed to detect all devices paired with your receivers, and at the very least display some basic information about them. At this moment, all [Unifying][unifying] receivers are supported (devices with USB ID `046d:c52b` or `046d:c532`) as are several Lightspeed Receivers and a dozen Nano receivers. ## HID++ HID++ is a Logitech-proprietary protocol that extends the standard HID protocol for interfacing with keyboards, mice, and so on. HID++ allows Logitech receivers to communicate with multiple devices and modify some features of the device on the device itself. As the HID++ protocol is proprietary many aspects of it are unknown. Some information about HID++ has been obtained from Logitech but even that is subject to change and extension. There are several versions of the HID++ and many different Logitech receivers and devices that utilize it. Different receivers and devices implement different portions of HID++ so even if two devices appear to be the same in both physical appearance and behavior they may working completely differently underneath. (For example, there are versions of the M510 mouse that use different versions of the HID++ protocol.) Contrariwise, two different devices may appear different physically but actually look the same to software. (For example, some M185 mice look the same to software as some M310 mice.) The software identity of a receiver can be determined by its USB id (reported by Solaar and also viewable in Linux using `lsusb`). The software identity of a device can be determined by its Wireless PID as reported by Solaar. Even something as fundamental as pairing works differently for different receivers. For Unifying receivers, pairing adds a new paired device, but only if there is an open slot on the receiver. So these receivers need to be able to unpair devices that they have been paired with or else they will not have any open slots for pairing. Some other receivers, like the Nano receiver with USB ID `046d:c534`, can only pair with particular kinds of devices and pairing a new device replaces whatever device of that kind was previously paired to the receiver. These receivers cannot unpair. Further, some receivers can pair an unlimited number of times but others can only pair a limited number of times. Only some connections between receivers and devices are possible. In should be possible to connect any device with a Unifying logo on it to any receiver with a Unifying logo on it. Receivers without the Unifying logo probably can connect only to the kind of devices they were bought with and devices without the Unifying logo can probably only connect to the kind of receiver that they were bought with. ## Supported features Solaar uses the HID++ protocol to pair devices to receivers and unpair devices from receivers. Solaar also uses the HID++ protocol to display features of receivers and devices. Solaar can modify some of the features of devices. Solaar currently only displays some features and can modify even fewer. Solaar does not do anything beyond using the HID++ protocol to change the behavior of receivers and devices. In particular, Solaar cannot change how the operating system turns the keycodes that a keyboard produces into characters that are sent to programs. That is the province of HID device drivers and other software (such as X11). Logitech receivers and devices have firmware in them. Some of the firmware can be updated using Logitech software in Windows. For example, there are security issues with some Logitech receivers and devices and Logitech has firmware updates to alleviate these problems. Some Logitech firmware can also be updated in Linux using `fwupdmgr`. WARNING: Updating firmware can cause a piece of hardware to to become permanently non-functional if something goes wrong with the update or the update installs the wrong firmware. Solaar does keep track of some of the changeable state of a device between invocations. When Solaar starts it restores on-line devices to their previously-known state. Also, while running Solaar restores devices to their previously-known state when the device comes on line. Querying a device for its current state can require quite a few HID++ interactions. These interactions can temporarily slow down the device, so Solaar tries to internally cache information about devices. If the device state is changed by some other means, even sometimes by another invocation of Solaar, this cached information may become incorrect. Currently there is no way to force an update of the cached information besides terminating Solaar and starting it again. ## Battery Icons For many devices, Solaar shows the approximate battery level via icons that show up in both main Solaar window and the system tray. Solaar used to use several heuristics to determine which icon names to use for this purpose, but as more and more battery icon schemes have been developed this has become impossible to do well. Solaar now uses the eleven standard battery icon names `battery-{full,good,low,critical,empty}[-charging]` and `battery-missing`. Solaar will use the symbolic versions of these icons if started with the option `--battery-icons=symbolic`. Because of bugs external to Solaar these symbolic icons may be nearly invisible in dark themes. [solaar]: https://github.com/pwr-Solaar/Solaar [logitech]: https://www.logitech.com [unifying]: https://en.wikipedia.org/wiki/Logitech_Unifying_receiver