| BMP280 | A digital barometric pressure and temperature sensor by Bosch. Communicates over I2C. |
| Bun | A JavaScript runtime and package manager used by the monitor application. |
| Chirp Spread Spectrum (CSS) | The modulation technique used by LoRa. Data is encoded into frequency sweeps (chirps) that are resistant to interference. |
| DIO1 | A pin on the SX1262 radio chip that pulses high when a packet has been received. Used for interrupt-driven receive. |
| ESP32 | A low-cost dual-core microcontroller by Espressif. Runs the Sensor Net firmware. |
| Flooding mesh | A mesh routing strategy where every node rebroadcasts any packet it has not already seen. Simple but uses more airtime than targeted routing. |
| GPIO | General-Purpose Input/Output. Physical pins on a microcontroller that can be configured as digital inputs or outputs. |
| hPa | Hectopascal. A unit of atmospheric pressure. 1 hPa = 100 Pa. Standard atmosphere is approximately 1013.25 hPa. |
| Hop | One relay step in the mesh network. A packet with hops=2 was relayed by two intermediate nodes before reaching the receiver. |
| I2C | Inter-Integrated Circuit. A two-wire serial protocol (SDA + SCL) for connecting low-speed peripherals to a microcontroller. |
| ISR | Interrupt Service Routine. A function triggered directly by hardware (such as the DIO1 pin going high). Runs immediately, interrupting the normal program flow. |
| Jitter | A random delay added before retransmitting a relayed packet. Prevents multiple nodes from relaying simultaneously and causing collisions. |
| LoRa | Long Range. A radio modulation technique by Semtech for low-power, long-range IoT communication. |
| Mesh network | A network topology where every node can relay packets for other nodes, extending coverage without a central router. |
| msg_id | A 32-bit unique identifier attached to each packet. Used for deduplication in the mesh. Computed as node_id XOR sequence_counter. |
| Nanopb | A C implementation of Protocol Buffers designed for embedded systems. Generates plain C structs with no dynamic memory allocation. |
| Non-blocking | Code that returns immediately rather than waiting inside a delay() call. All timing in Sensor Net uses millis() checks instead of blocking delays. |
| PlatformIO | A build system and package manager for embedded firmware projects. Manages compilers, board support, and library dependencies. |
| Protobuf | Protocol Buffers. A language-neutral binary serialization format by Google. Used for compact, versioned message encoding. |
| Ring buffer | A fixed-size FIFO data structure where new entries overwrite the oldest when the buffer is full. Used for the seen-message table. |
| RSSI | Received Signal Strength Indicator. A measurement of how strong a received radio signal is, in dBm. Closer to 0 = stronger. |
| SNR | Signal-to-Noise Ratio. The difference between the signal level and the background noise level, in dB. Higher = cleaner signal. LoRa can decode signals with negative SNR. |
| SPI | Serial Peripheral Interface. A four-wire high-speed serial bus used to communicate with the SX1262 LoRa radio chip. |
| Spreading Factor (SF) | A LoRa parameter that controls the range vs. data rate trade-off. Range: 7 (fastest, shortest range) to 12 (slowest, longest range). |
| SQLite | A lightweight, file-based relational database. The monitor application stores all sensor reports in a SQLite database. |
| SX1262 | Semtech’s LoRa radio transceiver chip. Used on the Heltec WiFi LoRa 32 V3 board. |
| Sync word | A LoRa network identifier. Only radios with the same sync word can communicate. Functions like a channel selector. |
| Tauri | A framework for building desktop applications with a web frontend (React/TypeScript) and a native backend (Rust). |
| TMP102 | A 12-bit I2C digital temperature sensor by Texas Instruments. Resolution: 0.0625 degrees C. |
| TTL | Time-To-Live. The maximum number of relay hops a packet can traverse before being dropped. Set by MESH_MAX_HOPS. |
| Vext | The peripheral power rail on the Heltec V3 board. Controlled by GPIO 36 (active LOW). Powers the OLED display and external peripherals. |
| Vite | A fast JavaScript bundler and development server. Used by the monitor application for the React frontend. |
