Print and optionally write offsets to duck_config

[kristof]

Here's how the script handles the JSON output and config file saving:

Step 1: Print the JSON Object

    print("=== New offsets ===")
    print(json.dumps({"joints_offsets": hwi.joints_offsets}, indent=2))
    print("===================")

After calibrating all joints, it prints the offsets as formatted JSON:

=== New offsets ===
{
  "joints_offsets": {
    "right_hip_yaw": 0.05,
    "right_hip_roll": -0.02,
    "right_hip_pitch": 0.03,
    ...
  }
}
===================

The indent=2 makes it human-readable with proper formatting.

---

Step 2: Ask to Save

    save = input(f"\nSave to {DUCK_CONFIG_PATH}? (Y/n): ").lower()
    if save == "y" or save == "":

Prompts the user: Save to ~/duck_config.json? (Y/n):

• Press Enter or Y → saves
• Press N → skips saving

---

Step 3: Load Existing Config (if it exists)

        if os.path.exists(DUCK_CONFIG_PATH):
            with open(DUCK_CONFIG_PATH, "r") as f:
                config = json.load(f)
        else:
            config = {}

Key behavior: It doesn't overwrite the entire file — it loads the existing config first. This preserves other settings like eyes, speaker, antennas, etc.

---

Step 4: Update Only joints_offsets

        # Update only the joints_offsets key
        config["joints_offsets"] = hwi.joints_offsets

Only the joints_offsets key is replaced. All other config values remain untouched.

---

Step 5: Write Back

        with open(DUCK_CONFIG_PATH, "w") as f:
            json.dump(config, f, indent=2)
        
        print(f"✓ Saved offsets to {DUCK_CONFIG_PATH}")

Writes the merged config back to the file with nice formatting.

---

Visual Flow

┌─────────────────────────────────────────────────┐
│  Calibration complete                           │
└─────────────────────────────────────────────────┘
                    │
                    ▼
        ┌───────────────────────┐
        │  Print JSON to console │  ← Always happens
        │  (copy-paste backup)   │
        └───────────────────────┘
                    │
                    ▼
        ┌───────────────────────┐
        │  Save to config? (Y/n) │
        └───────────────────────┘
               │         │
          Y/Enter        N
               │         │
               ▼         ▼
    ┌─────────────────┐  "Not saved. You can
    │ Load existing   │   copy the JSON above
    │ duck_config.json│   manually."
    │       │         │
    │       ▼         │
    │ Merge offsets   │
    │       │         │
    │       ▼         │
    │ Write file      │
    │       │         │
    │       ▼         │
    │ "✓ Saved..."    │
    └─────────────────┘

---

Why This Design?

1. Always prints JSON → You have a backup even if you don't save
2. Confirms before writing → Won't accidentally overwrite your config
3. Merges, doesn't replace → Preserves other config settings
4. Default is Yes → Pressing Enter saves (convenient for quick workflows)

⚠️ Why not write to the EEPROM of the servo?

• If you put offsets in a file, you always have:
  • Backups
  • Version history
  • Ability to reset to defaults instantly (for example when swapping a broken servo)
• Servo EEPROM usually supports ~100k writes (sometimes less).
  Writing them repeatedly will degrade the EEPROM.