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| 1 | +package bthome |
| 2 | + |
| 3 | +import ( |
| 4 | + "bytes" |
| 5 | + "encoding/binary" |
| 6 | + "errors" |
| 7 | + "fmt" |
| 8 | + "io" |
| 9 | +) |
| 10 | + |
| 11 | +/* |
| 12 | +* |
| 13 | +01 02 03 04 05 06 07 08 09 10 11 12 13 14 |
| 14 | +44 00 2c 01 64 05 14 05 00 2d 01 3f 00 00 |
| 15 | +0x01-0x01 44 = header |
| 16 | +0x02-0x03 00 = property type (packet id) |
| 17 | +0x03-0x04 2c = 44 packet id |
| 18 | +0x04-0x05 01 = property type (battery) |
| 19 | +0x05-0x06 64 = battery level 100% |
| 20 | +0x06-0x07 05 = property type (illuminance) |
| 21 | +0x07-0x0A 14 05 00 = the illuminance value |
| 22 | +0x0A-0x0B 2d = property type (window state) |
| 23 | +0x0B-0x0C 01 = 1 = Open 0 = Closed |
| 24 | +0x0C-0x0D 3F = property type (rotation) |
| 25 | +0x0D-0x0F 00 00 = rotation value 0 |
| 26 | +*/ |
| 27 | + |
| 28 | +// Parse - Parses bthome encoded data |
| 29 | +// https://bthome.io/format/#sensor-data |
| 30 | +func Parse(data []byte) (*SensorData, error) { |
| 31 | + if len(data) < 3 { |
| 32 | + return nil, fmt.Errorf("bthome: invalid data length: %d", len(data)) |
| 33 | + } |
| 34 | + |
| 35 | + r := bytes.NewReader(data) |
| 36 | + header, err := r.ReadByte() |
| 37 | + if err != nil { |
| 38 | + return nil, fmt.Errorf("bthome: failed to read header id: %w", err) |
| 39 | + } |
| 40 | + if header != 0x44 { |
| 41 | + return nil, fmt.Errorf("bthome: invalid header type: %d", header) |
| 42 | + } |
| 43 | + |
| 44 | + var sensorData SensorData |
| 45 | + for { |
| 46 | + propertyType, err := r.ReadByte() |
| 47 | + if err != nil { |
| 48 | + if errors.Is(err, io.EOF) { |
| 49 | + break |
| 50 | + } |
| 51 | + return nil, fmt.Errorf("bthome: failed to read property type: %d", propertyType) |
| 52 | + } |
| 53 | + |
| 54 | + switch propertyType { |
| 55 | + case 0x00: // packet id |
| 56 | + /** |
| 57 | + https://bthome.io/format/#misc-data |
| 58 | + * The packet id is optional and can be used to filter duplicate data. |
| 59 | + * This allows you to send multiple advertisements that are exactly the same, to improve the chance that the advertisement arrives. |
| 60 | + * BTHome receivers should only process the advertisement if the packet id is different compared to the previous one. |
| 61 | + * The packet id is a value between 0 (0x00) and 255 (0xFF), and should be increased on every change in data. |
| 62 | + * Note that most home automation software already have some other filtering for unchanged data. |
| 63 | + * The use of a packet id is therefore often not needed. |
| 64 | + **/ |
| 65 | + packetId, err := r.ReadByte() |
| 66 | + if err != nil { |
| 67 | + return nil, err |
| 68 | + } |
| 69 | + sensorData.PacketId = packetId |
| 70 | + case 0x01: // battery % |
| 71 | + battery, err := r.ReadByte() |
| 72 | + if err != nil { |
| 73 | + return nil, fmt.Errorf("bthome: failed to read battery: %w", err) |
| 74 | + } |
| 75 | + sensorData.BatteryPercent = battery |
| 76 | + case 0x05: // illuminance lux |
| 77 | + illuminance, err := readIlluminance(r) |
| 78 | + if err != nil { |
| 79 | + return nil, fmt.Errorf("bthome: failed to read illuminance: %w", err) |
| 80 | + } |
| 81 | + sensorData.IlluminanceLux = illuminance |
| 82 | + case 0x2D: // window bool |
| 83 | + windowState, err := r.ReadByte() |
| 84 | + if err != nil { |
| 85 | + return nil, fmt.Errorf("bthome: failed to read window state: %w", err) |
| 86 | + } |
| 87 | + sensorData.WindowState = windowState |
| 88 | + case 0x3A: // button |
| 89 | + var buttonEvent uint16 |
| 90 | + if err := binary.Read(r, binary.BigEndian, &buttonEvent); err != nil { |
| 91 | + return nil, fmt.Errorf("bthome: failed to read button event: %w", err) |
| 92 | + } |
| 93 | + sensorData.ButtonEvent = buttonEvent |
| 94 | + case 0x3F: // rotation ° |
| 95 | + var rotation int16 |
| 96 | + if err := binary.Read(r, binary.BigEndian, &rotation); err != nil { |
| 97 | + return nil, fmt.Errorf("bthome: failed to read rotation: %w", err) |
| 98 | + } |
| 99 | + sensorData.RotationDegrees = float32(rotation) / 10. |
| 100 | + default: |
| 101 | + return nil, fmt.Errorf("bthome: unknown property type: %d", propertyType) |
| 102 | + } |
| 103 | + } |
| 104 | + |
| 105 | + return &sensorData, nil |
| 106 | +} |
| 107 | + |
| 108 | +func readIlluminance(r io.Reader) (float32, error) { |
| 109 | + var component12 uint16 |
| 110 | + err := binary.Read(r, binary.BigEndian, &component12) |
| 111 | + if err != nil { |
| 112 | + return 0, err |
| 113 | + } |
| 114 | + |
| 115 | + var component3 byte |
| 116 | + err = binary.Read(r, binary.BigEndian, &component3) |
| 117 | + if err != nil { |
| 118 | + return 0, err |
| 119 | + } |
| 120 | + |
| 121 | + illuminance := uint32(component12)<<8 | uint32(component3) |
| 122 | + return float32(illuminance) / 100., nil |
| 123 | +} |
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