Add collapsible differential OTA example for Ikoka Stick

docs/ota_station_g2_to_ikoka_stick.md

@@ -160,6 +160,90 @@ application update needs no copy of the old firmware.
 This locally packaged application is unsigned and uses explicit manual
 installation; the separate bootloader package remains signed.
 
+<details id="differential-upgrade" markdown="1">
+<summary>Optional: differential firmware upgrade (smaller download)</summary>
+
+A differential update sends a patch from the Ikoka Stick's exact running
+application to the new application. It can reduce LoRa transfer time. The
+bootloader update in step 7 still uses the signed full bootloader package.
+
+Prepare the new binary and full package above first. Use this option only
+when you also have the **original application DFU ZIP for the firmware
+currently running on the Ikoka Stick**. A matching version label or a rebuild
+of the same commit is not enough. If that original file is unavailable, use
+the full update above.
+
+On **Ikoka Stick — Repeater Admin**, get its current identity:
+
+```text
+ver
+ota self
+```
+
+Copy the original application DFU ZIP onto **Raspberry Pi** as
+`downloads/ikoka-stick-33dbm-repeater-running.zip`. In the Pi terminal, paste
+the 16-character `base_hash` from that fresh `ota self` reply when prompted:
+
+```bash
+read -r -p 'Current Ikoka Stick base_hash (16 hex characters): ' IKOKA_BASE_HASH
+export IKOKA_BASE_HASH
+python3 - <<'PY'
+import hashlib, json, os, re, struct, zipfile
+from pathlib import Path
+expected = os.environ['IKOKA_BASE_HASH'].strip().upper()
+assert re.fullmatch(r'[0-9A-F]{16}', expected), 'Invalid base_hash'
+with zipfile.ZipFile('downloads/ikoka-stick-33dbm-repeater-running.zip') as archive:
+    app = json.loads(archive.read('manifest.json'))['manifest']['application']
+    image = archive.read(app['bin_file'])
+trailer = image[-56:]
+assert len(trailer) == 56 and trailer[:4] == b'EndF', 'Missing EndF'
+assert struct.unpack_from('<I', trailer, 4)[0] == len(image) - 56
+assert hashlib.sha256(image[:-56]).digest()[:8] == trailer[8:16], 'Body hash mismatch'
+assert struct.unpack_from('<I', trailer, 20)[0] == 0xE5331F02, 'Wrong application target'
+assert trailer[24:].rstrip(b'\0') == b'ikoka_stick_nrf_33dbm', 'Wrong board'
+assert trailer[8:16].hex().upper() == expected, 'This is not the running firmware'
+Path('inputs/ikoka-stick-33dbm-repeater-running.bin').write_bytes(image)
+print('Exact running application confirmed:', expected)
+PY
+```
+
+Stop if any check fails. Then build and check the **in-place** nRF52 delta:
+
+```bash
+motatool build \
+  --base inputs/ikoka-stick-33dbm-repeater-running.bin \
+  --fw inputs/ikoka-stick-33dbm-repeater.bin \
+  --patch-type in-place \
+  --out inputs/ikoka-stick-33dbm-repeater-delta.mota
+motatool verify inputs/ikoka-stick-33dbm-repeater-delta.mota
+motatool inspect inputs/ikoka-stick-33dbm-repeater-delta.mota
+ls -lh serve/ikoka-stick-33dbm-repeater.mota inputs/ikoka-stick-33dbm-repeater-delta.mota
+```
+
+Check `codec_id` is `2 (detools-in-place)`, `base_hash` matches the live Ikoka
+Stick, target is `E5331F02`, and the new version/hardware match the full
+package. Let motatool derive the safe workspace from the firmware; do not
+override its memory or target checks. Compare package sizes and keep the full
+update if the delta is not smaller. `verify` checks the delta container's
+integrity; it does not prove that you selected the running base image.
+
+To serve the delta, replace the full application package in the serving
+folder **before starting motatool**:
+
+```bash
+cp inputs/ikoka-stick-33dbm-repeater-delta.mota serve/ikoka-stick-33dbm-repeater.mota
+```
+
+Continue with steps 4–9. In step 8, choose the **application, delta** row and
+use its own eight-character manifest ID with `ota pull <APP_MID8> flash`,
+then `ota install` when ready. The target's `base_hash` must still match
+immediately before that pull. Updating only the bootloader in step 7 leaves
+the running application unchanged, so it does not invalidate the delta base.
+After installation, check the same new firmware version and expected
+post-install body hash printed earlier in step 3.
+
+</details>
+
 ## 4. Identify the Station G2's USB port
 
 On **Raspberry Pi — terminal**:

mkdocs.yml

@@ -112,6 +112,9 @@ nav:
           - Older releases: old-releases/index.md
       - Test Results: test-results/index.md
 
+markdown_extensions:
+  - md_in_html
+
 theme:
   name: material
   logo: _assets/meshcore.svg