A Raspberry and Logitech Jam

My old Logitech K750 keyboard has been with me for more than 12 years and is poised for a second life with a Raspberry Pi. What powered the keyboard all this time were the solar panels above the row of function keys. The collected energy, whether from daylight or lamplight, was stored in a Maxell ML2023 rechargeable button battery seen below:


ML2023 Rechargeable Battery

So far, I’ve only had to replace the battery twice, but Logitech (intentionally) did not make it easy, as I needed a spudger tool to gently pry the battery tray open. Do not use the similarly sized CR2023 battery, as it is not rechargeable and would pose a fire hazard.

Being solar powered, it follows that the keyboard would be wireless. Connection to a computer is over a 2.4GHz USB dongle, which Logitech calls a Unifying Receiver. Living up to the name, this receiver also let me connect an old Logitech M335 mouse.

While there were many Logitech models listed in the Raspberry Pi’s keyboard settings, there wasn’t one for the K750. Instead, I identified the keyboard as an Apple Aluminum ANSI keyboard and it worked perfectly, including recognizing the numpad.

The setup wouldn’t be complete without the Linux open source Solaar App which you can install from the Raspberry Pi Preferences menu:

Add Logitech Unifying Receiver

Similar to Logitech’s native Solar App for Mac and Windows, Solaar lets you monitor the status of your paired devices:

Solaar App


The screen shot above shows the M335 mouse and the K750 keyboard. The grayed-out K400 is not connected, and corresponds to a Logitech keyboard with a built-in track pad.

The Logitech K750 isn’t the mechanical siren that is the Nuphy Air75, but tactile feedback from its scissor switches (I think) is neat and precise. I also like that the space bar and control keys along the bottom are slightly convex, while most of the other keys are slightly concave. Missing, though, is a caps lock LED, presumably to limit power draw from the battery. Low power, however, was never a problem, even when typing in a darkened room.

If you don’t already own a K750, you can learn more about it from countless favorable reviews on the internet, including one written in 2012 on Macworld. Unfortunately, Logitech no longer makes this keyboard, and their website indicates it is out of stock.

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