qmk_firmware/keyboards/handwired/splittest/bluepill/keyboard.json

{
    "matrix_pins": {
        "cols": ["B1"],
        "rows": ["B10"]
    },
    "split": {
        "handedness": {
            "pin": "A7"
        }
    },
    "diode_direction": "COL2ROW",
    "development_board": "bluepill",
    "features": {
        "bootmagic": false,
        "mousekey": false,
        "extrakey": false,
        "console": true
    }
}