More information: read the article on Medium
reading the undocumented mems accelerometer on apple silicon macbooks via iokit hid
what is this
apple silicon chips (M1/M2/M3/M4) have a hard to find mems accelerometer managed by the sensor processing unit (SPU). it's not exposed through any public api or framework. this project reads raw 3-axis acceleration data at ~800hz via iokit hid callbacks.
only tested on macbook pro m3 pro so far - might work on other apple silicon macs but no guarantees
how it works
the sensor lives under AppleSPUHIDDevice in the iokit registry, on vendor usage page 0xFF00, usage 3. the driver is AppleSPUHIDDriver which is part of the sensor processing unit. we open it with IOHIDDeviceCreate and register an asynchronous callback via IOHIDDeviceRegisterInputReportCallback. data comes as 22-byte hid reports with x/y/z as int32 little-endian at byte offsets 6, 10, 14. divide by 65536 to get the value in g. callback rate is ~100hz
you can verify the device exists on your machine with:
ioreg -l -w0 | grep -A5 AppleSPUHIDDevice
quick start
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