phaten-audio/en/docs/dev_doc/EQ_Protocols/EQ_HID_Protocol.md

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Zero-Code Firmware Series EQ HID Control Protocol and Command Set	EQ HID control protocol for zero-code firmware series devices, including message structure, command set, and field descriptions for mode switching, parameter read/write, and device information retrieval.	EQ, HID, Control Protocol, Command Set, USB HID, XU316, Zero-Code Firmware, Phaten Audio

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Zero-Code Firmware Series EQ HID Control Protocol and Command Set

1. Protocol Foundation Specifications

1.1 Underlying Communication Protocol

Based on USB HID (Human Interface Device) protocol.

Parameter	Value
Report ID	0x01
Packet Size	64 bytes
Transfer Direction	Bidirectional (Host <-> Device)

1.2 Message Format and Data Transmission

Common Message Format All commands and responses follow the Report structure below:

Field	Bytes	Description
Report ID	1	Fixed as 0x01
Sync Header	1	Fixed as 0x77 (command start identifier)
Command Code	1	Indicates specific operation (e.g., 0x8A)
Data Area	61	Specific data content (unused bytes typically filled with 0)

Data Transmission Notes

• Byte Order: All multi-byte data is transmitted in Little Endian mode.
• Floating Point: Follows IEEE 754 float format.

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2. Protocol Command Set

2.1 Command Classification Overview

Command Code	Command Description	Direction	Function
0x8A	SET_EQ_MODE	Host→Device	Switch current EQ mode
0x8B	GET_EQ_MODE	Host→Device	Get current EQ mode information (mode number, gain, name)
0x8C	SET_MODE_GAIN_AND_NAME	Host→Device	Set overall gain and name for specified mode
0x8D	SET_EQ_PARAMS	Host→Device	Send single filter parameters
0x8E	GET_EQ_PARAMS	Host→Device	Read single filter parameters
0x8F	GET_DEVICE_INFO	Host→Device	Get device basic information (PID, VID, SN, etc.)
0x90	RESET_EQ_PARAMS	Host→Device	Reset EQ parameters (restore presets)

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3. Basic Function Command Details

3.1 Switch EQ Mode (0x8A)

Host Sends

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header
2	1	0x8A	Command code
3	1	Mode	Mode value 0-5: Preset modes 6-8: User modes 9: Bypass
4-63	60	Reserved	Reserved bytes (0x00)

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3.2 Get Current EQ Mode Information (0x8B)

Host Sends

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header
2	1	0x8B	Command code
3-63	61	Reserved	Reserved bytes (0x00)

Device Returns (Response)

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header 1
2	1	0x8B	Sync header 2 (echo command code)
3	1	Mode	Current mode value
4-7	4	Gain	Overall gain (int32, little endian, range 0~-50dB)
8-23	16	Name	Mode name (UTF-8 string)
24-63	40	Reserved	Reserved bytes

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3.3 Set Mode Overall Gain and Name (0x8C)

Host Sends

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header
2	1	0x8C	Command code
3	1	Mode	Target mode value (0-9)
4-7	4	Gain	Overall gain (int32, little endian)
8-23	16	Name	Mode name (UTF-8 string)
24-63	40	Reserved	Reserved bytes

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3.4 Send EQ Parameters (0x8D)

Host Sends

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header
2	1	0x8D	Command code
3	1	Mode	Mode value (0-9)
4	1	Band	Filter index (0-7)
5	1	Type	Filter type (see table below)
6-9	4	Freq	Center frequency Hz (float, little endian)
10-13	4	Q	Q value (float, little endian)
14-17	4	BW	Bandwidth Hz (float, little endian)
18-21	4	Gain	Gain dB (float, little endian)
22-63	42	Reserved	Reserved bytes

Filter Type Codes

Code	Type	Code	Type
0x00	Bypass	0x06	Band Reject
0x01	All Pass	0x07	Notch
0x02	Peak	0x08	Constant Q
0x03	Low Pass	0x09	Low Shelf
0x04	High Pass	0x0A	High Shelf
0x05	Band Pass

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3.5 Read EQ Parameters (0x8E)

Host Sends

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header
2	1	0x8E	Command code
3	1	Mode	Mode value (0-9)
4	1	Band	Filter index (0-7)
5-63	59	Reserved	Reserved bytes

Device Returns (Response)

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header 1
2	1	0x8E	Sync header 2 (echo command code)
3	1	Mode	Mode value
4	1	Band	Filter index
5	1	Type	Filter type
6-9	4	Freq	Center frequency (float, little endian)
10-13	4	Q	Q value (float, little endian)
14-17	4	BW	Bandwidth (float, little endian)
18-21	4	Gain	Gain (float, little endian)
22-63	41	Reserved	Reserved bytes

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3.6 Get Device Information (0x8F)

Host Sends

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header
2	1	0x8F	Command code
3-63	61	Reserved	Reserved bytes

Device Returns (Response)

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header 1
2	1	0x8F	Sync header 2 (echo command code)
3-4	2	PID	Product ID (uint16, little endian)
5-6	2	VID	Vendor ID (uint16, little endian)
7-22	16	Product	Product string (UTF-8)
23-38	16	Vendor	Vendor string (UTF-8)
39-54	16	SN	Serial number string (UTF-8)
55-63	9	Reserved	Reserved bytes

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3.7 Reset EQ Parameters (0x90)

Host Sends

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header
2	1	0x90	Command code
3	1	Mode	Mode number (0-9) 0xFF indicates reset all modes
4-63	60	Reserved	Reserved bytes

Device Returns (Response)

Byte Position	Length	Content	Description
0	1	0x01	Report ID
1	1	0x77	Sync header 1
2	1	0x90	Sync header 2 (echo command code)
3	1	Status	Status code (0x00=success, 0x01=failure)
4-63	60	Reserved	Reserved bytes

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