Koi (Casio Smart Outdoor Watch WSD-F10) and Ayu (Casio Pro Trek Smart WSD-F20) are a pair of humongous watches with secondary, daylight readable displays. The WSD-F20 has GPS while the WSD-F10 does not. The ports are experimental because of bricking issues.

WARNING: RISK OF BRICKING! READ BELOW --- This is not the Casio WSD-F21HR. That is a different watch, see medaka.

Description

Koi is Casio's first WearOS watch. It is huge. The WSD-F10 was the first watch to introduce a dual-layer display, which was then made popular by catfish. Ayu is the successor to koi and added GPS. Both watches have flat tyres at the bottom of their round displays, as well as charging indicator lights next to their magnetic charging connectors. While koi and ayu's straps mount in the same way, their different shape means that koi and ayu's straps aren't intercompatible. Make sure you buy the correct straps for your watch.

koi

Koi is a large watch with a single piece bezel. The front has labels for the 'tool' and 'app' buttons and a 'sensor' label next to the pressure sensor port.

ayu

Ayu's main differentiator is the addition of GPS, but the watch is also redesigned to be more in line with Casio's Pro Trek brand. The bezel is covered in text, on top of the text present on koi.

Second Display

The second display has 5 16-segment digits in the center, 4 7-segment digits at the bottom, a battery icon in the bottom left, a 21x7 pixel matrix at the top and two separator lines above and below the central large digits.

Timekeeping

Whenever the colour LCD is not on, the monochrome LCD comes on. This shows Date and day of week in the dot matrix, hours and minutes in the middle and seconds at the bottom. The separator lines are not shown normally.

'Timepiece' mode

It is possible to power off the main system while the secondary LCD continues to show the time. When in this mode, pressing the power button quickly will cause the backlight to come on for a few seconds. The separator lines are shown when in timepiece mode.

Data display mode

It is also possible to show arbitrary data on the dot matrix and central display. Under casio's software, this could show compass bearing, tide times, sunrise/sunset times, altitude (with altitude graph), air pressure (with air pressure graph) and calories burned.

When displaying arbitrary data, the bottom section instead shows hours and minutes with a colon separator.
Apart from the colon, the central display also has an apostrophe after the second digit and after the 3rd digit. The last digit of the central display only shows in arbitrary data mode, and is smaller than the main 4.
It is possible to write any number to the central 5 16-segment digits, and to show any combination of digits and punctuation.
It is possible to write up to 4 characters of text to the top dot matrix.
If text and numbers aren't sufficient, it is possible to write arbitrary graphics to the dot matrix and the central digits.

HARDWARE ISSUES

These watches are expensive and problematic. Buyer Beware!!!

BRICKING ISSUES

Bugs in the original WearOS software can cause these watches to brick themselves. While they seem to be quite stable under AsteroidOS, it seems that messing with the bootloader and continuing to use WearOS can cause the watches to corrupt their own bootloader and bootloop forever. Our only advice is to flash with extreme caution and chat on matrix before doing so.

WearOS activation bug

Other bugs in WearOS can cause the watch to get stuck at the WearOS activation screen after a factory reset. If this happens to your device, you can still flash AsteroidOS and it should work fine.

Display delamination issues

If you see a strange fuzzy or cracked look around the flat tyre, that is the display delaminating. This will cause the touch digitiser to fail. The watch is still usable, but you won't be able to tap the entire screen. Don't buy any watch where you can see this happening.

Getting USB

USB is not exposed on the outside of these watches.

koi

The USB access procedure is not known.

ayu

TODO!!!

Repair

The watches can be easily disassembled by removing 4 phillips screws on the back. The watch is sealed with a gasket, so water resistance is not compromised by disassembly. Replacement parts are available, but expensive.

Miscellaneous hardware docs

Keys

The central key is the power button. The top and bottom keys are volume up and down respectively.

Manually getting to fastboot

Hold the top key while powering on the watch. Navigate the menu using the top key and select using the power button.