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| 1 | +package bthome |
| 2 | + |
| 3 | +import ( |
| 4 | + "bytes" |
| 5 | + "encoding/binary" |
| 6 | + "errors" |
| 7 | + "fmt" |
| 8 | + "io" |
| 9 | +) |
| 10 | + |
| 11 | +const ( |
| 12 | + encryptionFlag = 1 << 0 |
| 13 | + triggerBasedDeviceFlag = 1 << 2 |
| 14 | + versionFlag = (1 << 3) - 1 |
| 15 | +) |
| 16 | + |
| 17 | +// Parse - Parses bthome encoded data |
| 18 | +// https://bthome.io/format/#sensor-data |
| 19 | +func Parse(data []byte) (*SensorData, error) { |
| 20 | + if len(data) < 3 { |
| 21 | + return nil, fmt.Errorf("bthome: invalid data length: %d", len(data)) |
| 22 | + } |
| 23 | + |
| 24 | + r := bytes.NewReader(data) |
| 25 | + header, err := r.ReadByte() |
| 26 | + if err != nil { |
| 27 | + return nil, fmt.Errorf("bthome: failed to read header id: %w", err) |
| 28 | + } |
| 29 | + capabilityFlags := readCapabilities(header) |
| 30 | + if capabilityFlags.Version != 2 { |
| 31 | + return nil, fmt.Errorf("bthome: unsupported bthome version: %d", capabilityFlags.Version) |
| 32 | + } |
| 33 | + |
| 34 | + var sensorData SensorData |
| 35 | + sensorData.CapabilityFlags = capabilityFlags |
| 36 | + for { |
| 37 | + propertyType, err := r.ReadByte() |
| 38 | + if err != nil { |
| 39 | + if errors.Is(err, io.EOF) { |
| 40 | + break |
| 41 | + } |
| 42 | + return nil, fmt.Errorf("bthome: failed to read property type: %d", propertyType) |
| 43 | + } |
| 44 | + |
| 45 | + switch propertyType { |
| 46 | + case 0x00: // packet id |
| 47 | + /** |
| 48 | + * https://bthome.io/format/#misc-data |
| 49 | + * The packet id is optional and can be used to filter duplicate data. |
| 50 | + * This allows you to send multiple advertisements that are exactly the same, to improve the chance that the advertisement arrives. |
| 51 | + * BTHome receivers should only process the advertisement if the packet id is different compared to the previous one. |
| 52 | + * The packet id is a value between 0 (0x00) and 255 (0xFF), and should be increased on every change in data. |
| 53 | + * Note that most home automation software already have some other filtering for unchanged data. |
| 54 | + * The use of a packet id is therefore often not needed. |
| 55 | + **/ |
| 56 | + packetId, err := r.ReadByte() |
| 57 | + if err != nil { |
| 58 | + return nil, err |
| 59 | + } |
| 60 | + sensorData.PacketId = packetId |
| 61 | + case 0x01: // battery % |
| 62 | + battery, err := r.ReadByte() |
| 63 | + if err != nil { |
| 64 | + return nil, fmt.Errorf("bthome: failed to read battery: %w", err) |
| 65 | + } |
| 66 | + sensorData.BatteryPercent = battery |
| 67 | + case 0x05: // illuminance lux |
| 68 | + illuminance, err := readIlluminance(r) |
| 69 | + if err != nil { |
| 70 | + return nil, fmt.Errorf("bthome: failed to read illuminance: %w", err) |
| 71 | + } |
| 72 | + sensorData.IlluminanceLux = illuminance |
| 73 | + case 0x21: // motion state |
| 74 | + motion, err := r.ReadByte() |
| 75 | + if err != nil { |
| 76 | + return nil, fmt.Errorf("bthome: failed to read motion state: %w", err) |
| 77 | + } |
| 78 | + sensorData.MotionState = motion |
| 79 | + case 0x2D: // window state |
| 80 | + windowState, err := r.ReadByte() |
| 81 | + if err != nil { |
| 82 | + return nil, fmt.Errorf("bthome: failed to read window state: %w", err) |
| 83 | + } |
| 84 | + sensorData.WindowState = windowState |
| 85 | + case 0x2E: // humidity % |
| 86 | + humidity, err := r.ReadByte() |
| 87 | + if err != nil { |
| 88 | + return nil, fmt.Errorf("bthome: failed to read humidity: %w", err) |
| 89 | + } |
| 90 | + sensorData.HumidityPercent = humidity |
| 91 | + case 0x3A: // button |
| 92 | + var buttonEvent uint16 |
| 93 | + if err := binary.Read(r, binary.BigEndian, &buttonEvent); err != nil { |
| 94 | + return nil, fmt.Errorf("bthome: failed to read button event: %w", err) |
| 95 | + } |
| 96 | + sensorData.ButtonEvent = buttonEvent |
| 97 | + case 0x3F: // rotation ° |
| 98 | + var rotation int16 |
| 99 | + if err := binary.Read(r, binary.BigEndian, &rotation); err != nil { |
| 100 | + return nil, fmt.Errorf("bthome: failed to read rotation: %w", err) |
| 101 | + } |
| 102 | + sensorData.RotationDegrees = float32(rotation) / 10. |
| 103 | + case 0x45: // temperature °C |
| 104 | + var temperature int16 |
| 105 | + if err := binary.Read(r, binary.BigEndian, &temperature); err != nil { |
| 106 | + return nil, fmt.Errorf("bthome: failed to read temperature: %w", err) |
| 107 | + } |
| 108 | + sensorData.TemperatureCelsius = float32(temperature) / 10. |
| 109 | + default: |
| 110 | + return nil, fmt.Errorf("bthome: unknown property type: %d", propertyType) |
| 111 | + } |
| 112 | + } |
| 113 | + |
| 114 | + return &sensorData, nil |
| 115 | +} |
| 116 | + |
| 117 | +func readCapabilities(capabilityFlags byte) CapabilityFlags { |
| 118 | + encryption := (capabilityFlags & encryptionFlag) != 0 |
| 119 | + triggerBasedDevice := (capabilityFlags & triggerBasedDeviceFlag) != 0 |
| 120 | + version := (capabilityFlags >> 5) & versionFlag |
| 121 | + return CapabilityFlags{ |
| 122 | + Encryption: encryption, |
| 123 | + TriggerBasedDevice: triggerBasedDevice, |
| 124 | + Version: version, |
| 125 | + } |
| 126 | +} |
| 127 | + |
| 128 | +func readIlluminance(r io.Reader) (float32, error) { |
| 129 | + var component12 uint16 |
| 130 | + err := binary.Read(r, binary.BigEndian, &component12) |
| 131 | + if err != nil { |
| 132 | + return 0, err |
| 133 | + } |
| 134 | + |
| 135 | + var component3 byte |
| 136 | + err = binary.Read(r, binary.BigEndian, &component3) |
| 137 | + if err != nil { |
| 138 | + return 0, err |
| 139 | + } |
| 140 | + |
| 141 | + illuminance := uint32(component12)<<8 | uint32(component3) |
| 142 | + return float32(illuminance) / 100., nil |
| 143 | +} |
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