Two Android-only BLE defects, both of which BlueZ hides and both of which
made a working Click pod look like broken hardware.
droidplug writes ENABLE_NOTIFICATION_VALUE to the CCCD whatever the
characteristic supports. A characteristic that indicates but does not
notify rejects that write, so the Click's Sync TX channel
(00000004-19ca-…, read/indicate) failed to subscribe on every pod with
"Unable to write descriptor". The patch picks the value from the
characteristic's properties.
droidplug also never calls requestMtu, so Android stayed at the 23-byte
default and a notification carried 20 bytes. The pods send up to 106.
Anything longer arrived truncated mid-field and failed to parse, which
looks exactly like a pod that has gone quiet — the frames were being cut
off, not withheld. Requesting 517 settles at 251 against this hardware,
and a 105-byte frame now arrives whole.
Both are applied by the sync script after it lifts the Java out of the
crate, each guarded by a grep that fails the sync loudly if upstream
moves the line rather than silently producing an unpatched build.
Also ignore the .gradle cache that IDE Gradle daemons drop into
src-tauri/android/app, which they mistake for a project root because of
the build.gradle.kts template living there.
Verified on the tablet: no subscribe failures, longest Click frame 105
bytes where the cap was 20, and both paddles shifting.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
G-4 said port to Android without rewriting the core, and nothing in
crates/core, crates/ble or crates/fit needed touching (NFR-5) — the
Android work is two files of glue and a Gradle project.
btleplug's Android backend is a hybrid crate: the GATT work happens in
Java and Rust drives it over JNI. `platform::init` has to run once with a
JNIEnv, and it cannot come from Rust's own startup — JNI resolves classes
with the calling thread's class loader, and a thread Rust spawned has
only the bootstrap loader. So MainActivity.onCreate calls into
src/android.rs, before super.onCreate: TauriActivity's super chain
synchronously starts the thread that runs `run()`, which builds AppState
and starts scanning while we are still in onCreate. Lose that race and
droidplug's global_adapter() — an `expect` — panics inside the scan task,
silently, for the life of the process.
Failing soft here is not enough for the same reason, so init sets a READY
flag and devices.rs asks before every call in. Bluetooth switched off at
launch then reads as an ordinary "no adapter", which the connection
screen already knows how to show, and onResume retries so switching it on
and coming back works.
The Java half is not a maven dependency. Upstream tells you to publish a
0.1.1-SNAPSHOT artifact to mavenLocal by hand, which no CI runner can
reproduce and which drifts from the crate silently — the failure is a
NoSuchMethodError at the first scan, not a build error. Instead
sync-android-sources.sh lifts the classes out of the btleplug and
jni-utils crate sources at exactly the versions in Cargo.lock, so a
mismatch is impossible by construction.
gen/ stays generated and untracked, so everything hand-written lives in
src-tauri/android/ and is copied back after each `tauri android init`.
check-android-sources.sh fails the build if a source exists only under
gen/ or differs from its tracked copy: both are files git has never seen
and the next init deletes, and the resulting APK builds, installs, and
behaves as though they were never written.
Permissions are split at API 31, because asking for one the platform does
not know is a permanent denial. neverForLocation on BLUETOOTH_SCAN is a
promise we can keep honestly: every scan filters by service UUID, so no
location permission is needed on Android 12+.
Also: tracing to logcat, since Android has no stdout and the default
writer drops every line into a closed fd.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Gears are expressed as an offset to the commanded gradient, leaving the
physics on the route's true gradient so shifting changes effort, not speed.
Neutral gear commands exactly the route gradient, so an un-shifted ride is
unchanged.
Cadence is not in FTMS on this trainer but is on its Zwift channel, decoded
against captured frames. The undeclared FTMS trailing bytes were ruled out:
wheel RPM restated at a fixed 73.8x speed.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Cargo workspace with core/ble/fit/probe crates. crates/core/src/types.rs
is the fixed contract between the BLE layer, ride engine and UI.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
dtourolleandClaude Opus 5