lora_msg_protocol.h

Go to the documentation of this file.

#ifndef LORA_MSG_PROTOCOL
#define LORA_MSG_PROTOCOL
 
#include "general/node_cfg.h"
 
#include <stdint.h>
 
// ============================================================================
// LoRa Message Types
// ============================================================================
// Message type IDs - use uint8_t for compact serialization
typedef enum
{
    LORA_REGISTRATION = 0x00,  // Registration of a new slave
    LORA_PERIODIC_INFO = 0x01, // Periodic status update (every 24h)
    LORA_ALARM = 0x02          // Alarm/tampering detected
} lora_msg_id_t;
 
// ============================================================================
// Wire Format Documentation (for TTN decoder)
// ============================================================================
/*
 * Wire format for LoRa messages. All values are little-endian.
 *
 * REGISTRATION MESSAGE (42 bytes total):
 *   Byte 0:      msg_type = 0x00
 *   Byte 1:      slave_id (0-15)
 *   Bytes 2-33:  device name as null-terminated string (32 bytes max)
 *   Bytes 34-37: longitude as int32 (multiply by 1e6 for actual value)
 *   Bytes 38-41: latitude as int32 (multiply by 1e6 for actual value)
 *
 * PERIODIC MESSAGE (2 + N*3 bytes, where N is the number of slaves):
 *   Byte 0:      msg_type = 0x01
 *   Byte 1:      slave_count (how many slaves follow)
 *   Then for each slave (i = 0 to slave_count-1):
 *     Byte 2+i*3:   slave_id
 *     Byte 3+i*3:   battery percentage (0-100)
 *     Byte 4+i*3:   moisture percentage (0-100)
 *   Max size is 50 bytes (for 16 slaves: 2 + 16*3 = 50)
 *
 * ALARM MESSAGE (2 bytes total):
 *   Byte 0:      msg_type = 0x02
 *   Byte 1:      slave_id of the device that triggered the alarm
 */
 
// ============================================================================
// C Struct Definitions (for internal use, not wire format)
// ============================================================================
 
// Status data for a single slave in periodic messages
typedef struct
{
    uint8_t slave_id;
    uint8_t battery_percentage;
    uint8_t moisture;
} periodic_slave_status_t;
 
// Registration message (internal representation)
typedef struct
{
    uint8_t msg_type; // LORA_REGISTRATION
    uint8_t slave_id;
    char name[32];
    int32_t longitude; // Fixed-point, multiply by 1e6
    int32_t latitude;  // Fixed-point, multiply by 1e6
} lora_reg_msg_t;
 
// Periodic status message (internal representation)
typedef struct
{
    uint8_t msg_type; // LORA_PERIODIC_INFO
    uint8_t slave_count;
    periodic_slave_status_t slaves[MAX_SLAVE_NUM];
} lora_periodic_msg_t;
 
// Alarm message (internal representation)
typedef struct
{
    uint8_t msg_type; // LORA_ALARM
    uint8_t slave_id;
} lora_alarm_msg_t;
 
// ============================================================================
// FIFO Packet for queuing LoRa messages
// ============================================================================
// This is written to lora_fifo by state machine / handlers
// and read by send_lora() to send the appropriate message
 
typedef struct
{
    uint8_t msg_type; // LORA_REGISTRATION, LORA_PERIODIC_INFO, or LORA_ALARM
    uint8_t slave_id; // Relevant for registration and alarm (ignored for periodic)
} lora_fifo_packet_t;
 
#endif // LORA_MSG_PROTOCOL