node-red-nodes/hardware/sensehatsim/examples/Compass.json

[
    {
        "id": "104a54e7.6656cb",
        "type": "rpi-sensehatsim out",
        "z": "7756eff1.08d0a",
        "name": "",
        "x": 470,
        "y": 300,
        "wires": []
    },
    {
        "id": "a3786fbb.b3ff9",
        "type": "rpi-sensehatsim in",
        "z": "7756eff1.08d0a",
        "name": "",
        "motion": true,
        "env": false,
        "stick": false,
        "x": 120,
        "y": 300,
        "wires": [
            [
                "931798d.9640d68"
            ]
        ]
    },
    {
        "id": "931798d.9640d68",
        "type": "function",
        "z": "7756eff1.08d0a",
        "name": "Compass",
        "func": "// Based on the Compass example provided by\n// the Sense HAT python library\n// https://github.com/RPi-Distro/python-sense-hat/tree/master/examples\n\nvar led_loop = [4, 5, 6, 7, 15, 23, 31, 39, 47, 55, 63, 62, 61, 60, 59, 58, 57, 56, 48, 40, 32, 24, 16, 8, 0, 1, 2, 3];\nvar led_degree_ratio = led_loop.length / 360.0;\nvar dir = (360 - msg.payload.compass)%360;\n\nfunction getXY(dir) {\n    var led_index = Math.floor(led_degree_ratio * (dir%360));\n    var offset = led_loop[led_index];\n    return [offset % 8,Math.floor(offset / 8)];\n}\n\nvar previous = context.get('previous');\nmsg.payload = '';\n\nvar position = getXY(dir);\nif (!previous || position[0] != previous[0][0] || position[1] != previous[0][1]) {\n    if (previous) {\n        msg.payload = previous[0][0]+\",\"+previous[0][1]+\",off,\"+\n                      previous[1][0]+\",\"+previous[1][1]+\",off,\";\n    } else {\n        msg.payload = \"*,*,off,\";\n    }\n    previous = [\n        position,\n        getXY(dir+180)\n    ];\n    msg.payload += previous[0][0]+\",\"+previous[0][1]+\",red,\"+\n                  previous[1][0]+\",\"+previous[1][1]+\",white\"\n    \n    context.set('previous',previous);\n    return msg;\n}\nreturn null;\n\n",
        "outputs": 1,
        "noerr": 0,
        "x": 280,
        "y": 300,
        "wires": [
            [
                "104a54e7.6656cb"
            ]
        ]
    },
    {
        "id": "434680a8.c2e54",
        "type": "comment",
        "z": "7756eff1.08d0a",
        "name": "Simple compass for Sense Hat",
        "info": "Generates a compass, showing north (red) and south (white).\n\nBased on the python example provided with the Sense Hat: https://github.com/RPi-Distro/python-sense-hat/tree/master/examples\n\nThe accuracy of the compass will depend on callibrating the Sense Hat\ninternal compass. Search the Sense Hat forums for a guide on how to\ndo this.\n",
        "x": 190,
        "y": 260,
        "wires": []
    }
]