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ri edited this page Apr 14, 2026 · 1 revision

USB Protocol

Note: On Linux, OpenWave uses wIndex=0x3303 instead of 0x3300 to bypass snd-usb-audio's interface ownership check. The firmware accepts both — see How it works for details.

Device

  • Vendor ID: 0x0FD9 (Elgato)
  • Product ID: 0x007D (Wave XLR), 0x007E (DFU mode)
  • Control Interface: Interface 3 — Class 0xFF, SubClass 0xF0, 0 endpoints
  • Audio Interfaces: 0-2 — standard USB Audio Class 1.0
  • DFU Interface: 4

Transport

All control communication uses USB Class requests on EP0:

  • Read: bmRequestType=0xA1 (IN, Class, Interface)
  • Write: bmRequestType=0x21 (OUT, Class, Interface)
  • bRequest: 0x85 (read), 0x05 (write)
  • wIndex: 0x3300 (protocol standard) / 0x3303 (Linux workaround)

NOT Vendor requests — the type bits are Class (01), not Vendor (10).

Commands

bmRequestType bRequest wValue wLength Description
0xA1 0x85 0x0000 34 Read config (all settings)
0xA1 0x85 0x0001 10 Read metering (input levels)
0xA1 0x85 0x000A 2 Read API version
0xA1 0x85 0x000A 51 Read device info (FW version, serial)
0x21 0x05 0x0000 34 Write config (read-modify-write)

Config Struct (34 bytes, wValue=0x0)

Offset Size Type Field Encoding
0-1 2 uint16 LE input_gain Internal scale, ~linear with dB. 0x0000=0dB, 0x2200≈31dB
2 1 uint8 unknown 0x00
3 1 uint8 unknown 0xEC
4 1 uint8 input_mute 0=unmuted, 1=muted
5-8 4 — reserved all 0x00
9-10 2 int16 LE headphone_volume Signed Q8.8 dB. Divide by 256 for dB. Range: -30.5 to 0 dB
11-13 3 — reserved all 0x00
14 1 uint8 volume_select 1=knob→gain, 2=knob→HP volume
15 1 uint8 unknown 0xFF (likely clipguard or lowcut)
16-17 2 — unknown 0x00 0x00
18-26 9 — unknown all 0xFF (likely DSP enable flags)
27 1 uint8 unknown 0x01
28 1 uint8 unknown 0x01
29 1 uint8 unknown 0xFF
30 1 uint8 unknown 0x37 (55)
31 1 uint8 unknown 0x00
32 1 uint8 unknown 0x01
33 1 uint8 low_impedance 0=disabled, 1=enabled

Gain Encoding (bytes 0-1)

Little-endian uint16, internal scale (not direct dB).

USB Value (LE) Approx dB
0x0000 0
0x2200 ~31
0x2980 ~39
0x48C0 ~73

WebSocket API reports range 0-75 dB.

Headphone Volume (bytes 9-10)

Little-endian signed int16, Q8.8 fixed-point dB.

USB Value (LE) dB
0xE180 -30.5
0xF100 -15.0
0xFE33 -1.8
0x0000 0.0

Metering Block (10 bytes, wValue=0x1)

Offset Size Type Field
0-3 4 uint32 LE input_level_left
4-7 4 uint32 LE input_level_right
8-9 2 uint16 LE flag (always 0x0001)

Both levels are identical (mono mic). Range: ~0x00-0xFF.

Device Info Block (wValue=0xA)

Short read (2 bytes): returns API version, e.g. 01 03 = v1.3.

Full read (51 bytes):

Offset  Meaning
0-1     API version (01 03)
6-8     Firmware version (03 07 03 = v3.7.3?)
27-46   Device UID + serial number (ASCII)
47-50   Hardware info

Polling Pattern

Wave Link polls at 10 Hz (100ms interval):

  1. Read config (wValue=0x0, 34 bytes)
  2. Read meters (wValue=0x1, 10 bytes)
  3. Sleep ~100ms
  4. Repeat

No device-push notifications — purely host-polled.

Startup / Reconnect Sequence

  1. Read API version (wValue=0xA, 2 bytes)
  2. Read config (wValue=0x0, 34 bytes)
  3. Read meters (wValue=0x1, 10 bytes)
  4. Read full device info (wValue=0xA, 51 bytes)
  5. Read config again
  6. Write config (wValue=0x0, 34 bytes) — restores saved settings
  7. Begin steady-state 10 Hz polling

Write Protocol

Read-modify-write — always read the full 34-byte config first, modify desired bytes, write back the entire struct.

Unmapped Parameters

From binary analysis of Wave Link, these exist but byte offsets are unknown:

  • Clipguard enable, Low-cut enable
  • Headphone mute, Direct monitor level
  • Phantom power (48V), Gain lock
  • LED brightness/colors
  • DSP effects (compressor, EQ, expander) — likely use additional wValue addresses

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