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

[{"id":"b3b88507.4c4778","type":"rpi-sensehat out","z":"ec37e354.13c82","name":"","x":469,"y":30,"wires":[]},{"id":"e00b82a.f1ff48","type":"rpi-sensehat in","z":"ec37e354.13c82","name":"","motion":true,"env":false,"stick":false,"x":99,"y":30,"wires":[["3571a1b3.ca8e5e"]]},{"id":"3571a1b3.ca8e5e","type":"function","z":"ec37e354.13c82","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":279,"y":30,"wires":[["b3b88507.4c4778"]]}]