Feature: DroneCAN DNA (Dynamic Node Allocation) Server

[daijoubu]

Summary

Implement a DroneCAN DNA allocation server in INAV to enable plug-and-play support for peripherals that ship configured for dynamic node allocation (node_id=0).

Background

Many DroneCAN peripherals ship with node_id=0, expecting an allocator to assign them an ID at runtime. Currently, users must manually configure each peripheral's node ID. A DNA server in INAV would automatically handle this.

The DroneCAN specification supports two allocator modes:

• Non-redundant (single) - Simple, suitable for flight controllers
• Redundant (Raft) - Complex, for multi-allocator fault-tolerant networks

INAV should implement non-redundant mode - the spec explicitly states this is valid.

How DNA Allocation Works

1. Anonymous node (node_id=0) broadcasts Allocation request
   - first_part_of_unique_id = true
   - unique_id contains first 6 bytes of 16-byte UID

2. Server receives request, echoes back unique_id bytes
   - Node sends next chunk (first_part_of_unique_id = false)

3. After all 16 bytes matched, server assigns node_id
   - Look up existing allocation or assign new ID
   - Broadcast Allocation with node_id set
   - Node becomes active

Data Structures

// Allocation table entry
typedef struct {
    uint8_t unique_id[16];      // Node's unique identifier
    uint8_t node_id;            // Assigned node ID (1-125)
    uint8_t flags;              // Valid flag, etc.
} dnaAllocationEntry_t;

// Server state
typedef struct {
    dnaAllocationEntry_t entries[DNA_MAX_NODES];  // Allocation table
    uint8_t pendingUniqueId[16];    // UID being accumulated
    uint8_t pendingOffset;          // Bytes received so far
    uint8_t nextAvailableId;        // Next ID to assign (counts down from 125)
    timeMs_t lastRequestTime;       // For timeout handling
} dnaServer_t;

#define DNA_MAX_NODES 8             // Support up to 8 dynamic peripherals

Storage: 8 entries × 18 bytes = 144 bytes + state ≈ 170 bytes

Settings

- name: dronecan_dna_server
  description: "Enable DNA allocation server for plug-and-play DroneCAN peripherals"
  default_value: OFF
  field: dna_server_enabled
  type: bool

- name: dronecan_dna_max_nodes
  description: "Maximum dynamic node allocations"
  default_value: 8
  min: 1
  max: 16

Implementation Phases

Phase	Task	Effort
1	Data structures	1 hour
2	Request handler	2-3 hours
3	Integration into dronecan.c	1-2 hours
4	Settings	30 min
5	Persistence (optional)	2 hours
6	Testing	2-3 hours
Total		6-10 hours

Files to Create/Modify

• New: src/main/drivers/dronecan/dronecan_dna_server.c
• New: src/main/drivers/dronecan/dronecan_dna_server.h
• Modify: src/main/drivers/dronecan/dronecan.c - Add handler
• Modify: src/main/fc/settings.yaml - Add settings

Reference Implementation

ArduPilot: libraries/AP_DroneCAN/AP_DroneCAN_DNA_Server.cpp

• Stores allocations in flash (1KB area)
• Supports up to 125 nodes
• Uses FNV-1a hash for fast UID lookup

Target Version

INAV 10.x (optional feature)