I don't have a C11 macropad, but Pilaf asked me on the customMK Discord if I could help, so I took an educated guess at what the JSON should contain to be able to work with VIA, and Pilaf has confirmed that it works!
It looks like C11 exists entirely outside of the QMK/VIA ecosystem (possibly because it integrates wireless?), so I don't see VIA incorporating the C11 VIA JSON file anytime soon. That just means that you'll need to manually import the JSON file into VIA every time you want to reassign the keys. Regardless, to get VIA to recognize the C11, copy and paste the text below into notepad, save it as something like "C11.json", and then import the JSON file into VIA:
{
"name": "C11 by Cary Works",
"vendorId": "0x8101",
"productId": "0x4311",
"lighting": "qmk_rgblight",
"matrix": { "rows": 2, "cols": 6 },
"layouts": {
"keymap": [
["0,0", "0,1", "0,2", "0,3", "0,4", "0,5"],
[{"x":0.5},"1,0", "1,1", "1,2", "1,3", "1,4"]
]
}
}
Edit June 2, 2022: It looks like there are multiple versions of the C11 with different USB VID and PIDs. Since those are what VIA uses to identify a specific keyboard, if the above text doesn't work for a JSON file, try this instead:
{
"name": "C11 by Cary Works",
"vendorId": "0x1EA7",
"productId": "0x7777",
"lighting": "qmk_rgblight",
"matrix": { "rows": 2, "cols": 6 },
"layouts": {
"keymap": [
["0,0", "0,1", "0,2", "0,3", "0,4", "0,5"],
[{"x":0.5},"1,0", "1,1", "1,2", "1,3", "1,4"]
]
}
}