Software

There is no first-party software support for the Leopold FC660C—all functionality is hardware based. This is why the Hasu controllers are even a thing, and you can head over to this web-based TMK configurator to start customization of the keyboard if you have done the Hasu mod. The keyboard and controller are recognized immediately, which is always a good sign showing things are working well thus far. There is a handy guide on Github which explains the key mapping further; it is quite useful since some of the options may seem confusing by themselves. There are up to eight programmable layers, including the base layer which comes pre-populated as seen in the video above. The other layers are empty (TRNS, short for transparent) to begin with, and any assignment done here also needs to have a function on the base layer to switch over to the new layer(s). We see a lot of options, not only to allow for media playback and volume shortcuts, but also Fn keys, program shortcuts, macros, and mouse actions. There is also the ability to control how the actuation works, be it by holding down a key to initiate an action, tapping another key instead for something else and so on. Play with the options here, fill out the layers as desired, and do read the guide on Github to be sure you haven't messed up.


With the new firmware file downloaded, you now need to install the flashing tool for the Atmel USB microcontroller used on the Hasu board, which can since the takeover be found on the Microchip website. Unfortunately, even though it mentions there is a version including Java runtime environment, you will only find a standalone installer for Windows or Linux that has you separately install Java if not already on your system. With the installation done, you now need to press the flashing button on the back of the keyboard and manually select the new file to flash it onto the microcontroller. At this point, the keyboard is still in firmware flashing mode, so go ahead and do a physical disconnect of the USB cable and re-connect it to now have the keyboard running on the new firmware. This is clearly not a beginner-friendly approach to customization, and why we see larger companies dedicate entire teams to developing software programs based on the skeleton file from the hardware manufacturer.

Performance

The Leopold FC660C supports 6-key rollover USB (+1 modifier) out of the box, which goes up to NKRO with the Hasu mod, both of which tested successfully using Aqua's test. Switch Hitter confirmed no chatter with these keys either, and you can see above what functions get dedicated keys on the base layer before any customization.

This is effectively a tale of two keyboards: the Leopold FC660C as it comes in the retail packaging and it with the Hasu mod that allows more customization. That's not to say there is nothing you can do with the FC660C as-is since there are also pre-programmed functions associated with layers, which is where the front-facing legends come into play. The vast majority are associated with the Fn key layer, and a couple with the Esc key. Then there are the dip switches which trade some key positions as well as lock or unlock the Win key. I would rather remap the Win key instead of losing a whole precious key, especially as the dip switches on the back are not the easiest to toggle without tools. Then there's the key layout we discussed before, with two keys using up a lot of space inefficiently for my books. Making it worse is the use of one of those keys for Insert, which is barely used in typical typing to begin with and often just a detriment. Leopold does need to update the keyboard to allow for native key mapping and layers as a first-party feature, and change over to USB Type-C connectivity while you are at it!


The form factor and keycaps are not what you are buying the FC660C for; it is obviously for the Topre switches. For those interested, KeyChatter has a nice primer on Topre switches, which provides a good base for understanding these electrostatic capacitive switches. These are switches with a rubber dome for tactile feedback that work based on the measured capacitance without any metal parts touching each other, which results in consistent, reproducible typing over long periods of time. Varmilo came up with a novel EC switch that is a hybrid of this and the more standard mechanical switch design, which allows them to decouple the feedback mechanisms outside of actuation. But with the expiration of the Topre switch patent over 15 years ago, it was only a matter of time before we saw alternatives with the same tactile design as was the case with NIZ and its Plum keyboards as well as the i-Rocks version with the K70E before.

Topre did have a few tricks up its sleeve in introducing a silent version of its switches, all of which still relish pedigree in the keyboard market today. The feel of these switches is of course subjective and can only really be described in words since I can't relate the sensory feedback objectively otherwise. Compared to the average membrane switch that some may want to compare these to, these feel a lot better throughout, and not having to bottom out is always a good thing. That said, it is easier said than done with the stock 45 gf springs; the force-travel curve will indicate as much since the minute you get past the tactile feedback, the conical spring collapses upon itself. The tactile feedback is consistent and satisfying, and calling it a refined membrane switch would not be too big a stretch, which is why we see a lot of such comments online. During the review of the NIZ Plum, I wasn't able to fully compare those clone switches to the OG. Not so now, and I have to say that Niz comes really close but Topre is still the better typing experience. These silent versions are also a fantastic modification for those who want the Topre experience to be quieter than even with the usual switch.


Speaking of which, let's talk about the typing experience and how the LeopoldFC660C Low Noise sounds. As always, the sound of a keyboard is based on more than just the switch type. So when comparing sound clips, consider the keyboard as a whole. In this case, I have provided above an example sound clip of me typing on the keyboard sample at ~85 WPM as it comes out of the box with the Topre 45g Silent switches. For context, you can find sound clips from other keyboards here, including those with tactile switches. There is very little stopping you from bottoming out, but it still does not feel or sound like a 45 gf mechanical switch—the Cherry MX Brown is probably the most popular analogue. What you get here is a far deeper thock when bottoming out, with a crisp snap with the upstroke. The stabilizers are also very good, even if not quite lubed from what I see. All this makes the FC660C Low Noise keyboard an extremely quiet one, which is perfect for the work environment as long as these keys and the form factor are for you.