Protocol Buffer Definitions

The Nano uses Protocol Buffers for structured data serialization. Below are the key message and enum definitions used in the device communication.

Message Types

Basic Values

message IntegerValue {
  int32 value = 1;
}

message StringValue {
  string value = 1;
}

message BoolValue {
  bool value = 1;
}

Sensor Data

message SensorValue {
  int32 value = 1;        // Scaled by 10 for temperatures
  UnitType units = 2;     // Temperature unit
  SensorType type = 3;    // Type of sensor
}

message SensorValueList {
  repeated SensorValue values = 1;
}

Device Information

message FirmwareInfo {
  string commit_id = 1;   // Git commit hash
  string tag = 2;        // Version tag
  int32 date_code = 3;   // Build date code
}

message DeviceStatus {
  CookingState state = 1;
  int32 target_temp = 2;  // Scaled by 10
  int32 current_temp = 3; // Scaled by 10
  int32 timer_remaining = 4;
  UnitType unit = 5;
}

Enumerations

Temperature Units

enum UnitType {
  CELSIUS = 0;
  FAHRENHEIT = 1;
}

Device States

enum CookingState {
  IDLE = 0;
  PREHEATING = 1;
  COOKING = 2;
  TIMER_COMPLETE = 3;
  ERROR = 4;
}

Sensor Types

enum SensorType {
  WATER_TEMP = 0;
  TRIAC_TEMP = 1;
  AMBIENT_TEMP = 2;
}

Command Domains

enum DomainType {
  CONFIG = 1;  // Configuration domain
}

Usage in BTLE Communication

Encoding Commands

When sending a command with a payload:

1. Serialize the appropriate protocol buffer message
2. Combine with domain and message type bytes
3. COBS encode the complete message
4. Append a zero byte terminator

Example process for setting temperature to 65.5°C:

1. Create IntegerValue with value 655 (65.5 × 10)
2. Serialize to binary format
3. Prepend [CONFIG_DOMAIN, SET_TEMP_SETPOINT]
4. COBS encode
5. Append 0x00 terminator
6. Transmit over BTLE

Decoding Responses

When receiving a response:

1. Collect all chunks until message is complete
2. Remove terminator byte (0x00)
3. COBS decode
4. Extract domain and message type
5. Parse remaining payload using appropriate protocol buffer type

Example process for decoding sensor values:

1. Collect complete message
2. COBS decode
3. Extract domain and message type
4. Parse payload as SensorValueList
5. Process each sensor reading

Best Practices

Scale Factors

When working with temperature values:

// Encoding
scaled_temp = temperature_celsius * 10

// Decoding
actual_temp = sensor_value.value / 10.0

Message Handling

1. Define Protocol

   // Using appropriate language-specific protobuf library
   Define message types according to the schema above

2. Serialize Messages

   // Using protobuf serialization in your language
   Convert message object to binary data

3. Handle Responses

   // Using protobuf parsing in your language
   Parse binary data into appropriate message type

Message Size

Remember that BLE has a 20-byte MTU limit. Large protocol buffer messages will be automatically chunked during transmission.

Temperature Scale

For the Nano device, temperature values use a scale factor of 10 (not 100 as in other devices).