yamete-sensor-kickstart

What it is: a tiny open-source helper that kickstarts the built-in BMI286 accelerometer on Apple Silicon MacBooks so the Yamete App Store build can read its 100Hz report stream.

Why you need it: Yamete on the Mac App Store runs under App Sandbox. The sandbox silently blocks the IORegistry writes that tell the accelerometer to start reporting, so inside the sandbox Yamete cannot wake the sensor on its own. Until something outside the sandbox kickstarts the sensor, the adapter reports as unavailable and the app falls back to microphone + headphone-motion only.

Who should install it: users on an M1 / M2 / M3 / M4 MacBook Air or MacBook Pro who want the tactile detection channel (desk slaps and taps picked up through the laptop chassis) in addition to the microphone. On Macs without the BMI286 (iMac, Mac Mini, Mac Studio, Mac Pro, Intel Macs), this helper does nothing useful. There is no sensor to kickstart.

Who should NOT install it: anyone who is not comfortable compiling a ~250-line Swift source file and installing a LaunchDaemon as root. The microphone detection path in the App Store build works on every Mac with zero setup, and headphone-motion works whenever AirPods / Beats are connected. You don't need this helper for Yamete to function.

Report issues (please!)

If this helper doesn't work on your Mac, we want to know. The AppleSPUHIDDriver property surface is undocumented. Apple can change it at any macOS update, and it is physically only available on a subset of Apple Silicon MacBooks we haven't all tested. Verification relies on the community.

File a report here: https://github.com/Studnicky/yamete/issues/new

Please include:

• Your Mac model: e.g., "MacBook Pro 14-inch, M2 Pro, 2023". The "About This Mac" dialog has all of this.
• Your macOS version: full string including the point release, e.g. 14.5 (23F79).
• What you were expecting vs. What happened: one line each is fine.
• Output of the probe command, before and after running kickstart:

/usr/local/libexec/yamete-sensor-kickstart probe
/usr/local/libexec/yamete-sensor-kickstart kickstart
/usr/local/libexec/yamete-sensor-kickstart probe

• The last 20 lines of the LaunchDaemon log (after a reboot if you can reproduce the issue at boot):

tail -20 /var/log/yamete-sensor-kickstart.log

• The last 20 lines of the Yamete app log (helpful for cross- referencing the probe result with what Yamete actually saw):

tail -20 "$HOME/Library/Containers/com.studnicky.yamete/Data/Library/Application Support/Yamete/logs/yamete-$(date +%Y-%m-%d).log"

Reports on Macs where this does work are just as valuable as reports where it doesn't. We are building a known-working matrix and every data point helps.

Safety notes

1. This is an open-source helper, not an Apple-sanctioned interface. The three property writes it issues (ReportInterval, SensorPropertyReportingState, SensorPropertyPowerState on the AppleSPUHIDDriver service) are Apple-internal driver commands. They are invoked via public IOKit functions with no private API imports, but the property keys themselves are undocumented. A future macOS update can change or remove this surface without warning.
2. It runs as root via a LaunchDaemon. That is necessary because LaunchDaemons execute outside of any user's App Sandbox. Review the source (yamete-sensor-kickstart.swift) before running the installer if you want to audit exactly what it does. It is short enough to read in a few minutes.
3. It does not touch the network, write to user data, load kexts, install launch agents as other users, or persist anything other than the LaunchDaemon plist + the compiled binary. The install paths are /usr/local/libexec/yamete-sensor-kickstart and /Library/LaunchDaemons/com.studnicky.yamete.sensor-kickstart.plist. The uninstall script removes both.
4. sudo is required for the install and uninstall scripts. You will be prompted for your admin password.

Files in this directory

• yamete-sensor-kickstart.swift. The helper source (single file, uses only Foundation and IOKit). Implements four subcommands:
• probe. Report whether the sensor is currently streaming
• kickstart. One-shot: write the activation properties and exit
• deactivate. One-shot: stop streaming (for testing)
• daemon. Long-lived: run kickstart on startup, then subscribe to IOKit system power notifications via IORegisterForSystemPower and re-run kickstart on every wake event. This is how the shipping LaunchDaemon invokes the helper.
• com.studnicky.yamete.sensor-kickstart.plist. The LaunchDaemon plist. RunAtLoad = true, KeepAlive = true, ProcessType = Background. the helper starts at boot in daemon mode, kickstarts the sensor once, then parks itself in CFRunLoopRun waiting for wake notifications. Idle CPU cost is zero (it is asleep on a run loop). Logs to /var/log/yamete-sensor-kickstart.log.
• install.sh. Compiles the Swift file with swiftc, copies the binary to /usr/local/libexec/, copies the plist to /Library/LaunchDaemons/, and loads it with launchctl bootstrap.
• uninstall.sh. Unloads the LaunchDaemon and removes both files plus the log.

Installation

Download all four files into a fresh directory and run:

chmod +x install.sh uninstall.sh
./install.sh

The installer will:

1. Verify the Mac is arm64 (Apple Silicon).
2. Compile yamete-sensor-kickstart.swift with swiftc.
3. Smoke-test the compiled binary against the probe subcommand.
4. Unload any previously-installed version of the LaunchDaemon.
5. Copy the binary and plist to their system locations (sudo prompt).
6. Load the LaunchDaemon with launchctl bootstrap (triggers RunAtLoad . The daemon starts, kickstarts the sensor immediately, and registers its wake watcher).
7. Probe the sensor again to confirm the kickstart succeeded.

If the final probe succeeds, launch or relaunch Yamete. Open the menu bar dropdown, expand the Sensors section, and toggle Accelerometer on. You should see the accelerometer detecting desk taps alongside the microphone.

From the next reboot onward, the LaunchDaemon starts automatically at boot and Yamete picks up the live sensor without any further action. The daemon runs for the whole session. It re-runs the kickstart on every wake event so sleep / lid close / display sleep cannot cool it out from under the app.

Uninstallation

./uninstall.sh

This unloads the LaunchDaemon, removes the installed files, and removes the log. After uninstall, the accelerometer goes cold on the next reboot and Yamete silently falls back to microphone + headphone-motion.

Troubleshooting

probe: active=false after installing The LaunchDaemon may have run before the IOKit service matching became ready. Try forcing it to run again:

sudo launchctl kickstart -k system/com.studnicky.yamete.sensor-kickstart
/usr/local/libexec/yamete-sensor-kickstart probe

probe: no AppleSPUHIDDriver dispatchAccel=Yes service found Your Mac doesn't have the BMI286 accelerometer (iMac, Mac Mini, Mac Studio, Mac Pro, or Intel Mac). The helper won't help on this hardware; Yamete will run on microphone + headphone-motion only.

error: this helper is only useful on Apple Silicon Macs The installer detected an Intel architecture. Even if you're running the Intel build of macOS on Apple Silicon via Rosetta (you shouldn't be), the IOKit calls need native arm64. Nothing to do here.

Yamete still doesn't show the Accelerometer in the Sensors list Open the Yamete menu bar dropdown once after the helper has run. The sensor availability is probed when the dropdown opens. Also make sure you toggled the Accelerometer row on. The helper kickstarts the hardware but doesn't change Yamete's settings.

Does the sensor survive sleep/wake? Yes, two ways:

1. On the hardware we have tested, the BMI286 sits in Apple Silicon's always-on power domain and streams continuously at 100Hz across lid close / open cycles with no intervention. Verified empirically: a 35-second sleep period showed _num_events incrementing at the full 100 events/sec rate throughout sleep.
2. Defense in depth: the daemon subscribes to IOKit system power notifications via IORegisterForSystemPower and re-runs kickstart() on every kIOMessageSystemHasPoweredOn event. Even if a future macOS revision or a specific hardware configuration starts cooling the sensor during sleep, the daemon will re-run the kickstart the moment the system finishes waking.

You can confirm the wake handler is firing by tailing the log across a sleep cycle:

tail -f /var/log/yamete-sensor-kickstart.log
# ... close the lid, wait, open the lid ...
# expect a new line: "... daemon: system has powered on (re-running kickstart)"

If you ever see the sensor going cold despite the daemon running, please file an issue with your Mac model, macOS version, and the last 20 lines of /var/log/yamete-sensor-kickstart.log.

License

This helper is released under the MIT License (same as Yamete itself). Do whatever you like with it.