Scarlet build guide

 

Testing your PCB

Check that your PCB and daughterboard are working by connecting the PCB to your computer, installing the VIA Configurator application, navigating to the Key Tester tab, enabling Test Matrix, and bridging each key on the PCB by touching the two pads beside each hotswap socket or by inserting a switch into the PCB and pressing on the switch stem.

If the PCB is not recognized by VIA, begin troubleshooting steps by first flashing the VIA firmware onto the PCB using the QMK Toolbox application. If QMK Toolbox does not detect the PCB after entering DFU mode either by holding down esc while plugging the PCB into your computer or by shorting the two gold RST pads on the bottom of the PCB, then either the microcontroller on the PCB has failed, the JST cable is defective, or (very unlikely) the USB-C daughterboard is defective. If you require further help with troubleshooting, feel free to ask in our Discord server or contact us directly.

 

Installing stabilizers

Install your stabilizers into the PCB, required for left shift, spacebar, right shift, enter, and backspace. It is recommended to insert switches and keycaps for each stabilizer to test them for rattle and other undesirable stabilizer noise as they cannot be uninstalled after assembly, making tuning and other modifications more difficult or impossible.

Note: Durock V2 stabilizers are larger than Cherry spec and are known to cause issues. Scarlet's plates have larger cutouts to accommodate Durock V2 stabilizers. However, the larger footprint of Durock V2 stabilizers requires the enter stabilizer to be installed before the right shift stabilizer.

Scarlet assembly

 

Inserting switches

Insert your switches into the plate and PCB, ensuring that the switch is fully seated into the plate and clipped in, and that the PCB is resting up against the switches for maximum contact with the hotswap sockets. When using a soft plate material such as POM and polycarbonate, you may need to pull up on the plate to ensure the switches are clipped into the plate as the flexible nature of the plate will bend downwards as the switch is inserted, causing the switch to not be clipped in properly.

While the Scarlet PCB reinforces the hotswap sockets by adhering them to the PCB using an epoxy, it is still recommended to support the sockets by holding the socket using your index finger while inserting the switch with your thumb. This will prevent any forces from pushing the socket away from the PCB.

Note: the multi-layout hotswap PCB requires certain switches to be flipped upside-down in a North-facing orientation. These switches include regular caps lockleft control, left windowsleft alt, and spacebar for 7u spacebar; and right windows, right menu, and right control for 6.25u spacebar.

Scarlet assembly

 

Installing the daughterboard

Take the USB-C daughterboard and insert one end of the JST cable into the JST connector on the daughterboard. Place the daughterboard into the bottom case with the USB-C connector facing upwards, then fasten it to the case using the included black M2x3mm screws. The other end of the JST cable should be inserted into the JST connector on the bottom of the Scarlet PCB.

In the event that the daughterboard needs to be replaced, such as a loose USB-C connector, any C3-revision Unified USB-C daughterboard will work. The earlier C2 revision may be compatible with Scarlet, however, it lacks features such as ESD, over-current, and over-voltage protection.

Note: remember to be careful when disassembling the keyboard as you can accidentally pull the JST connector off the daughterboard or main PCB if you pull too quickly and with too much force.

Daughterboard

 

Mounting: top mount

After installing your stabilizers and switches into the PCB, the PCB assembly will need to be mounted to the case. For a firmer typing experience and higher pitched sound signature, the plate can be screwed to the top case using the included silver colored M2x4mm screws.

Modifications to top mount include burger mount, where small silicone o-rings are placed between the plate and top case to isolate the plate from the case for acoustics, between the plate and screw for a cushioned feel, or both. As Scarlet uses a daughterboard for the USB-C port, burger mount with an o-ring between the plate and top case will not cause the USB-C port to be misaligned when the PCB assembly shifts downwards. Burger mount is recommended to be employed with longer M2x6mm screws as the o-rings will decrease the amount of threading the screws have to hold onto.

Scarlet top mount

 

Mounting: gasket mount

For a softer typing experience, lower pitched sound signature, and reduced case reverb, the PCB assembly can be mounted using gasket mount. The included silicone gasket is wrapped around the PCB assembly between the plate and PCB, and then rests on the bottom case at the semi-circle mounting posts around the perimeter. Ensure that the plate is not screwed to the top case as this will prevent the gasket from cushioning the keystrokes by compressing and allowing the plate to shift downwards. The top case is then installed, pushing the plate down and securing the PCB assembly in place. If you experience difficulty fully closing the top case, tuck the silicone gasket into the PCB and plate assembly and ensure it does not sit too far out.

For an even softer typing experience—and in some configurations an even lower pitched sound signature—an ultra-soft 20A silicone gasket is available as an add-on item. Different configurations of silicone hardnesses, mounting styles, and plate materials will dramatically change the overall feel and sound of Scarlet. Boba switches have commonly been recommended by users to be paired with a stiffer and higher pitched plate such as aluminum compared to POM, while the soft and muted nature of POM and gasket mount complement linear switches.

Even further customization can be had with custom plate materials such as FR4, carbon fiber, and copper. The plate outline file is available for those who want to manufacture their own plates.

Gasket mount

 

Assembling the case

Place the top case over the bottom case, ensuring the top case is flush with the bottom. Next, flip the case over. It is recommended to use the ledge on the sides and rear of the case for more leverage and easier handling.

Scarlet assembly

Fasten the eight included black M2x6mm screws from the bottom. Next, apply the four included 3M bumpon feet.

Note: for a deeper sound signature, the bumpons can be omitted. Beware that this exposes the case to scratches as it will make direct contact with the surface it sits on. It is recommended only to do this with a deskmat.

Scarlet case bottom

 

Installing your keycaps

The final step is to install your keycaps.

The keycaps shown in the render is ePBT Samurai.

Scarlet keyboard kit

 

Customizing the keymap and macros

The Scarlet PCB firmware is compatible with QMK, VIA, and Remap, allowing you to customize your keymap and macros without the use of proprietary software. Use VIA for on-the-fly key remapping and macro customization, or use Remap to perform all of those functions in a browser, removing the need for a dedicated application.

Note: Remap is currently limited to browsers that support the WebHID API.

 

Congratulations!

You have assembled your Scarlet keyboard kit and it is now ready for use. We hope you enjoy this keyboard, and encourage you to experiment with custom plate materials and mounting styles to tailor the sound and typing experience of Scarlet to your personal preferences.