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emeet-pixyd

HID Protocol

The EMEET PIXY exposes a HID interface over /dev/hidraw*. The daemon uses this for camera mode control, audio mode selection, and gesture toggling.

Device Identification

Section titled “Device Identification”

The PIXY presents as USB vendor 328f with product 00c0 (original PIXY) or 0118 (PIXY 2K) — both expose the same HID control interface. The daemon probes /sys/class/hidraw matching this vendor/product pair (plus any IDs listed in EMEET_PIXYD_EXTRA_PRODUCT_IDS); other EMEET products are recognized but never receive vendor bytes — see Supported Devices.

Command Structure

Section titled “Command Structure”

Each command consists of:

  1. A 9-byte config report written to the hidraw device
  2. A commit report to trigger execution
  3. A 200ms sleep between reports to respect the device’s processing time

Responses are 64-byte reads parsed by byte position.

Bidirectional Communication

Section titled “Bidirectional Communication”

The daemon supports both writing (sending commands) and reading (querying state) over the same hidraw device.

Writing

Section titled “Writing”
// Config report: 9 bytes
// Commit report: triggers execution
// 200ms sleep between them

Reading

Section titled “Reading”
// 64-byte response read
// Parsed by byte position

Operations

Section titled “Operations”

Set Camera State

Section titled “Set Camera State”

Controls the camera mode:

Mode Description
Tracking AI face tracking enabled
Idle Camera on, no tracking
Privacy Hardware lens shutter engaged

Set Audio Mode

Section titled “Set Audio Mode”

Controls the audio processing:

Mode Value Description
NC nc Noise cancellation + DSP
Live live Raw audio
Original original Original mode

Set Gesture

Section titled “Set Gesture”

Toggles gesture control on/off.

Error Handling

Section titled “Error Handling”
  • HID send failures trigger a probeDevices() re-scan to find the correct device path
  • The HIDDevice interface embeds fmt.Stringer — every implementation must provide String() for error context
  • queryHIDState[T] is a generic function for type-safe HID queries
  • Errors include dev=%s context for the device path

Generic HID Query

Section titled “Generic HID Query”
func queryHIDState[T any](dev HIDDevice, query []byte, parse func([]byte) T) (T, error)

This generic function abstracts the write-read-parse pattern for type-safe HID queries.

Concurrency

Section titled “Concurrency”

HID access is serialized by Daemon.hidMu (sync.Mutex). This ensures only one HID operation runs at a time, preventing protocol corruption from concurrent writes.

The lock is separate from the V4L2 lock (v4l2Mu) so that the 200ms HID sleep does not block PTZ commands.

Where to go next

Section titled “Where to go next”