phaten-audio/en/docs/dev_doc/protocols/XMOS_EQ_HID_Protocol.md

---
title: XMOS EQ HID Communication Protocol Specification
description: 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.
keywords: EQ, HID, Control Protocol, Command Set, USB HID, XU316, Zero-Code Firmware, Phaten Audio
authors:
  - admin
tags:
  - Protocol
  - XMOS
  - EQ
  - HID
search:
  boost: 2
---

# XMOS EQ HID Communication Protocol Specification

--8<-- "common/phaten_xmos_support_img.md"

## Protocol Overview :material-file-document-outline:

!!! abstract "Functional Scope and Purpose"
    This document provides detailed specifications for the communication protocol between XMOS EQ HID devices and PC-based GUI software. The protocol offers a complete feature set for EQ mode control, parameter configuration, and device information retrieval.

## 1. Protocol Foundation Specification :material-connection:

### 1.1 Underlying Communication Protocol

**Based on USB HID (Human Interface Device) Protocol**

| Parameter | Value |
|:---------------:|:--------------------:|
| Transmission Method | USB HID |
| Data Packet Size | 64 bytes (including 1-byte Report ID 0x01) |
| Effective Data | 63 bytes |
| Byte Order | Little Endian |
| Sync Header | 0x77 (fixed at byte 1, Report ID at byte 0) |

### 1.2 HID Device Identification

| Parameter | Value | Description |
|:----------:|:--------:|:-----------------------------------------:|
| Usage Page | 0xff82 or 0xff83 | HID device type identifier |
| Report ID | 0x01 | First byte (byte 0) when sending |
| Transmission Mode | Non-blocking mode | Prevents GUI freezing |

### 1.3 Communication Mechanism

!!! warning "Data Transmission Notes"
    - All data is transmitted in Little Endian byte order
    - Sync header 0x77 is fixed at byte 1 (byte 0 is Report ID = 0x01)
    - Recommend minimum 5ms interval between commands to avoid device processing delays

### 1.4 Data Packet Structure

!!! note "64-Byte Packet Convention"
    - Both PC requests and device responses use fixed-length 64-byte packets
    - Byte 0 is fixed as `report_id = 0x01`
    - Byte 1 is fixed as `sync_header = 0x77`
    - Byte 2 is `cmd_header` (command header)
    - All unused bytes must be padded with 0

## 2. Protocol Command Set :material-code-tags:

### 2.1 Command Classification Overview

!!! note "Command Usage Instructions"
    1. All commands must include Report ID 0x01 (byte 0) and sync header 0x77 (byte 1)
    2. Total packet length is fixed at 64 bytes (including Report ID)
    3. Unused bytes must be padded with 0

#### 2.1.1 Command Header Definitions

| Command Header | Command Name | Function Description | Direction |
|:------:|:--------:|:--------:|:----:|
| 0x8A | SET_EQ_MODE | Switch current EQ mode | PC → Device |
| 0x8B | GET_EQ_MODE | Get current EQ mode information (mode number, gain, name) | PC → Device |
| 0x8C | SET_MODE_GAIN_AND_NAME | Set overall gain and name for specified mode | PC → Device |
| 0x8D | SET_EQ_PARAMS | Send single filter parameters | PC → Device |
| 0x8E | GET_EQ_PARAMS | Read single filter parameters | PC ↔ Device |
| 0x8F | GET_DEVICE_INFO | Get basic device information (PID/VID/SN) | PC ↔ Device |
| 0x90 | RESET_EQ_PARAMS | Reset EQ parameters (restore presets) | PC ↔ Device |
| 0x91 | GET_EQ_MODE_COUNT | Get EQ mode count information | PC ↔ Device |
| 0x92 | SET_AND_SAVE_EQ_MODE | Set and save EQ mode | PC ↔ Device |
| 0x93 | SET_VOLUME | Set device volume level | PC → Device |
| 0x94 | GET_VOLUME | Get device volume level | PC ↔ Device |
| 0x95 | GET_LED_INFO | Get LED information (index and name) | PC ↔ Device |
| 0x96 | SET_LED_SWITCH | Set LED switch | PC ↔ Device |
| 0x97 | GET_LED_SWITCH | Get LED switch status | PC ↔ Device |
| 0x98 | GET_LED_STATUS | Get LED status (RGB/display status) | PC ↔ Device |
| 0x99 | GET_LED_COUNT | Get LED total count | PC ↔ Device |
| 0x9A | GET_UAC_MODE_INFO | Get UAC mode information (count and names) | PC ↔ Device |
| 0x9B | SET_UAC_MODE | Set UAC mode | PC → Device |
| 0x9C | GET_CURRENT_UAC_MODE | Get current UAC mode | PC ↔ Device |
| 0x9D | SET_EQ_ENABLE | Set EQ enable switch | PC ↔ Device |
| 0x9E | GET_EQ_ENABLE | Get EQ enable switch | PC ↔ Device |
| 0x9F | GET_SAMPLE_FORMAT | Get sample rate and format | PC ↔ Device |
| 0xA0 | SET_GAIN_MODE | Set gain mode | PC → Device |
| 0xA1 | GET_GAIN_MODE | Get gain mode | PC ↔ Device |
| 0xA2 | SET_FILTER_MODE | Set filter mode | PC → Device |
| 0xA3 | GET_FILTER_MODE | Get filter mode | PC ↔ Device |
| 0xA4 | SET_GAME_MODE | Set game mode | PC → Device |
| 0xA5 | GET_GAME_MODE | Get game mode | PC ↔ Device |
| 0xA6 | GET_FIRMWARE_VERSION | Get firmware version | PC ↔ Device |
| 0xA7 | SET_EQ_BAND_COUNT | Set EQ band count | PC → Device |
| 0xA8 | GET_EQ_BAND_COUNT | Get EQ band count | PC ↔ Device |
| 0xB0 | SET_EX3D_CMD | Set EX3D command | PC ↔ Device |
| 0xB1 | GET_EX3D_CMD | Get EX3D command | PC ↔ Device |
| 0x80 | SET_UPSAMPLE | Set sampling rate upsampling | PC → Device |
| 0x81 | GET_UPSAMPLE | Get sampling rate upsampling status | PC ↔ Device |

### 2.2 Detailed Command Formats

#### 2.2.1 Switch EQ Mode (0x8A)

**Function**: Switch current EQ mode

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8A |
| 3 | 1 | mode | Mode value (0-6: preset modes, 7-9: user modes) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.2 Get Current EQ Mode Information (0x8B)

**Function**: Get current mode value, overall gain, and mode name

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8B |
| 3 | 1 | mode | Mode value (0-9: specified mode; 0xFF: get current mode info) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8B (echo) |
| 3 | 1 | mode | Current mode value |
| 4-7 | 4 | gain | Overall gain (int32, little endian, range -50dB ~ 0dB) |
| 8-23 | 16 | name | Mode name (UTF-8 string) |
| 24-63 | 40 | reserved | Reserved fields (fill with 0) |

**Usage Notes**:

- Send `mode = 0xFF` to return the currently active EQ mode information
- Send `mode = 0-9` to return the specified mode gain and name (does not switch the current mode)

#### 2.2.3 Set Mode Overall Gain and Name (0x8C)

**Function**: Set overall gain and name for target mode

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8C |
| 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 fields (fill with 0) |

#### 2.2.4 Set EQ Parameters (0x8D)

**Function**: Send single filter parameters

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8D |
| 3 | 1 | mode | Mode value (0-9) |
| 4 | 1 | band | Filter index (0-7) |
| 5 | 1 | type | Filter type code |
| 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 fields (fill with 0) |

**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 |  |  |

**Data Format Notes**:

!!! info "Floating Point and Byte Order"
    - All floating-point numbers follow IEEE 754 float standard with little endian byte order
    - All multi-byte integers use Little Endian byte order

#### 2.2.5 Read EQ Parameters (0x8E)

**Function**: Read parameters of specified filter

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8E |
| 3 | 1 | mode | Mode value (0-9) |
| 4 | 1 | band | Filter index (0-7) |
| 5-63 | 59 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8E (echo) |
| 3 | 1 | mode | Mode value |
| 4 | 1 | band | Filter index |
| 5 | 1 | type | Filter type code |
| 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 | 41 | reserved | Reserved fields (fill with 0) |

#### 2.2.6 Get Device Information (0x8F)

**Function**: Get basic device identification information

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8F |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x8F (echo) |
| 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 fields (fill with 0) |

#### 2.2.7 Reset EQ Parameters (0x90)

**Function**: Reset EQ parameters for specified mode or all modes

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x90 |
| 3 | 1 | mode | Mode number (0-9, 0xFF = reset all modes) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x90 (echo) |
| 3 | 1 | status | Status code (0x00=success, 0x01=failure) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.8 Get EQ Mode Count (0x91)

**Function**: Get total EQ modes and preset mode count (excluding disabled modes)

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x91 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x91 (echo) |
| 3 | 1 | total | Total modes (e.g., 0-9 means 10 modes) |
| 4 | 1 | preset_total | Preset mode count (e.g., 0-6 means 7 presets) |
| 5-63 | 59 | reserved | Reserved fields (fill with 0) |

#### 2.2.9 Set and Save EQ Mode (0x92)

**Function**: Set current EQ mode and save to Flash, automatically restored on power up

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x92 |
| 3 | 1 | mode | Mode value (e.g., 0-9; 0-6 presets, 7-9 user) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x92 (echo) |
| 3 | 1 | status | Status code (0x00=success, 0x01=failure) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.10 Set Volume Level (0x93)

**Function**: Set device output volume level

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x93 |
| 3 | 1 | volume | Volume level (0-60) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Parameter Description**:

- Volume level range: 0-60 (total 61 levels)
- 0: Minimum volume (approx -127.5dB)
- 60: Maximum volume (0dB)

#### 2.2.11 Get Volume Level (0x94)

**Function**: Read current device volume level

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x94 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x94 (echo) |
| 3 | 1 | volume | Current volume level (0-60) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.12 Get LED Information (0x95)

**Function**: Read LED index and LED name

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x95 |
| 3 | 1 | led_index | LED index (0-7) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x95 (echo) |
| 3 | 1 | led_index | LED index (0-7) |
| 4-19 | 16 | led_name | LED name (UTF-8 string) |
| 20-63 | 44 | reserved | Reserved fields (fill with 0) |

#### 2.2.13 Set LED Switch (0x96)

**Function**: Set LED switch status

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x96 |
| 3 | 1 | led_index | LED index (0-7) |
| 4 | 1 | onoff | LED switch (0=OFF, 1=ON) |
| 5-63 | 59 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x96 (echo) |
| 3 | 1 | status | Status code (0x00=success, 0x01=failure) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.14 Get LED Switch Status (0x97)

**Function**: Read LED switch status

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x97 |
| 3 | 1 | led_index | LED index (0-7) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x97 (echo) |
| 3 | 1 | led_index | LED index (0-7) |
| 4 | 1 | onoff | LED switch (0=OFF, 1=ON) |
| 5-63 | 59 | reserved | Reserved fields (fill with 0) |

#### 2.2.15 Get LED Status (0x98)

**Function**: Read LED RGB color and display status

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x98 |
| 3 | 1 | led_index | LED index (0-7) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x98 (echo) |
| 3 | 1 | led_index | LED index (0-7) |
| 4 | 1 | r | R color value (0-255) |
| 5 | 1 | g | G color value (0-255) |
| 6 | 1 | b | B color value (0-255) |
| 7 | 1 | led_status | LED status (0=Off, 1=Solid, 2=Slow Flash, 3=Fast Flash, 4=Breathing) |
| 8-63 | 56 | reserved | Reserved fields (fill with 0) |

#### 2.2.16 Get LED Total Count (0x99)

**Function**: Read total number of LEDs supported by device

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x99 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x99 (echo) |
| 3 | 1 | led_total | Total LEDs |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.17 Get UAC Mode Information (0x9A)

**Function**: Read UAC mode count and name list

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9A |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9A (echo) |
| 3 | 1 | count | Total UAC modes (e.g., 2) |
| 4-11 | 8 | name0 | Mode 0 name (UTF-8, max 8 bytes) |
| 12-19 | 8 | name1 | Mode 1 name (UTF-8, max 8 bytes) |
| 20-63 | 44 | reserved | Reserved fields (fill with 0) |

#### 2.2.18 Set UAC Mode (0x9B)

**Function**: Set UAC mode (UAC1.0/UAC2.0)

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9B |
| 3 | 1 | uac_mode | UAC mode value (0=UAC2.0, 1=UAC1.0) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Device Processing**:

- Note: Device will not send response after reboot

#### 2.2.19 Get Current UAC Mode (0x9C)

**Function**: Read current UAC mode and name

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9C |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9C (echo) |
| 3 | 1 | uac_mode | Current UAC mode value (0=UAC2.0, 1=UAC1.0) |
| 4-11 | 8 | uac_name | Current UAC mode name (UTF-8, max 8 bytes) |
| 12-63 | 52 | reserved | Reserved fields (fill with 0) |

#### 2.2.20 Set EQ Enable Switch (0x9D)

**Function**: Set EQ enable switch (Enable/Disable)

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9D |
| 3 | 1 | enable | EQ Enable (0=OFF, 1=ON) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9D (echo) |
| 3 | 1 | status | Status code (0x00=success, 0x01=failure) |
| 4 | 1 | enable | Current EQ enable status (0=OFF, 1=ON) |
| 5-63 | 59 | reserved | Reserved fields (fill with 0) |

#### 2.2.21 Get EQ Enable Status (0x9E)

**Function**: Read current EQ enable status

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9E |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9E (echo) |
| 3 | 1 | enable | Current EQ enable status (0=OFF, 1=ON) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.22 Get Sampling Format (0x9F)

**Function**: Read current audio sampling rate and format

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9F |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x9F (echo) |
| 3-6 | 4 | samp_rate | Sampling rate (uint32, little endian, e.g., 48000) |
| 7-10 | 4 | samp_format | Sample format (uint32, little endian) |
| 11-63 | 53 | reserved | Reserved fields (fill with 0) |

#### 2.2.23 Set Gain Mode (0xA0)

**Function**: Set gain adjustment mode (input gain/output gain)

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA0 |
| 3 | 1 | gain_mode | Gain mode (0=Input Gain, 1=Output Gain) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.24 Get Gain Mode (0xA1)

**Function**: Read current gain adjustment mode

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA1 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA1 (echo) |
| 3 | 1 | gain_mode | Current gain mode (0=Input Gain, 1=Output Gain) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.25 Set Filter Mode (0xA2)

**Function**: Set DAC filter mode

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA2 |
| 3 | 1 | filter_mode | Filter mode value (0-7) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Filter Mode Definitions**:

- 0: Minimum Phase filter (default)
- 1: Linear Phase Apodizing Fast Roll-off filter
- 2: Linear phase fast roll-off filter
- 3: Linear Phase Fast Roll-off low-ripple filter
- 4: Linear phase slow roll-off filter
- 5: Minimum phase fast roll-off filter
- 6: Minimum phase slow roll-off filter
- 7: Minimum Phase Fast Roll-Off Low Dispersion

#### 2.2.26 Get Filter Mode (0xA3)

**Function**: Read current DAC filter mode

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA3 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA3 (echo) |
| 3 | 1 | filter_mode | Current filter mode (0-7) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.27 Set Game Mode (0xA4)

**Function**: Set game mode

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA4 |
| 3 | 1 | game_mode | Game mode (0=No effect, 1=FPS, 2=Virtual 7.1) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.28 Get Game Mode (0xA5)

**Function**: Read current game mode

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA5 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA5 (echo) |
| 3 | 1 | game_mode | Current game mode (0=No effect, 1=FPS, 2=Virtual 7.1) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.29 Get Firmware Version (0xA6)

**Function**: Read device firmware version (BCD format)

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA6 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA6 (echo) |
| 3 | 1 | major_bcd | Major version (BCD, e.g. 0x01 means 1) |
| 4 | 1 | minor_bcd | Minor version (BCD, e.g. 0x00 means 0) |
| 5 | 1 | patch_bcd | Patch version (BCD, e.g. 0x0C means 12) |
| 6-63 | 58 | reserved | Reserved fields (fill with 0) |

**Version Format Description**:

- Version uses BCD (Binary Coded Decimal) format
- Example: `0x01 0x00 0x0C` represents version `1.0.12`

#### 2.2.30 Set EQ Band Count (0xA7)

**Function**: Set EQ band count. Supports dynamic switching among 8/16/24/32 bands to control how many DSP cores participate in processing.

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA7 |
| 3 | 1 | band_count | EQ band count (8=Core0 only, 16=Core0+Core1, 24=Core0+Core1+Core2, 32=all 4 cores) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Device Processing**:

- Only accepts 8, 16, 24, 32; other values are rejected
- Saved to Flash (independent file `eq_band_cnt`) and restored on power-up

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA7 (echo) |
| 3 | 1 | status | Status code (0x00=success, 0x01=failure) |
| 4 | 1 | band_count | Current EQ band count (8/16/24/32) |
| 5-63 | 59 | reserved | Reserved fields (fill with 0) |

#### 2.2.31 Get EQ Band Count (0xA8)

**Function**: Read current EQ band count

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA8 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xA8 (echo) |
| 3 | 1 | band_count | Current EQ band count (8/16/24/32) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

#### 2.2.32 Set EX3D Command (0xB0)

**Function**: Send EX3D set command, encapsulating all EX3D SET commands

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xB0 |
| 3-6 | 4 | ex3d_cmd | EX3D command code (includes SET flag, refer to ex3d_protocol.md) |
| 7-10 | 4 | param1 | Parameter 1 (depends on EX3D command) |
| 11-14 | 4 | param2 | Parameter 2 (depends on EX3D command) |
| 15-18 | 4 | param3 | Parameter 3 (depends on EX3D command) |
| 19-63 | 45 | reserved | Reserved or extended parameters |

**EX3D Command Code Description**:

- Base command range: 0x80-0x94
- SET command format: `Base Command & ~0x0100` (clear 9th bit)
- Supported SET commands:
  - 0x81: CMD_OPEN (Open EX3D)
  - 0x82: CMD_ONOFF (Set EX3D Switch)
  - 0x83: CMD_ANGLE (Set Angle)
  - 0x84: CMD_SOUND_FIELD (Set Sound Field)
  - 0x85: CMD_MUTE (Set Mute)
  - 0x86: CMD_ON_GAIN (Set On Gain)
  - 0x87: CMD_LMT_THRESHOLD (Set Limiter Threshold)
  - 0x88: CMD_UPMIX (Set Upmix)
  - 0x89: CMD_LFE (Set LFE Gain)
  - 0x8A: CMD_OFF_GAIN (Set Off Gain)
  - 0x8E: CMD_LMT_ATTACKK_TIME (Set Limiter Attack Time)
  - 0x8F: CMD_LMT_RELEASE_TIME (Set Limiter Release Time)
  - 0x90: CMD_TEST_CANCEL (Cancel Test)
  - 0x91: CMD_TEST_STEP (Test Step)
  - 0x92: CMD_TEST_ROTATE (Test Rotate)
  - 0x93: CMD_EXPAND_GAIN (Set Expand Gain)
  - 0x94: CMD_REDUCE_GAIN (Set Reduce Gain)

**Device Processing**:

- Parses EX3D command code, extracts base command and parameters
- Calls corresponding EX3D handler (hid_receive_task_in_c)
- Executes setting operation based on command type

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xB0 (echo) |
| 3 | 1 | status | Status code (0x00=success, 0x01=failure) |
| 4-7 | 4 | ex3d_cmd | EX3D command code (echo) |
| 8-11 | 4 | result | Return value (some commands return 0xFFFFFFFF for parameter error) |
| 12-63 | 52 | reserved | Reserved fields |

**Usage Instructions**:

- This command unifies all EX3D setting commands
- Parameter format consistent with original EX3D protocol
- For detailed EX3D command descriptions, refer to ex3d_protocol.md

#### 2.2.33 Get EX3D Command (0xB1)

**Function**: Read EX3D parameters, encapsulating all EX3D GET commands

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xB1 |
| 3-6 | 4 | ex3d_cmd | EX3D command code (includes GET flag, refer to ex3d_protocol.md) |
| 7-10 | 4 | param1 | Parameter 1 (depends on EX3D command, e.g., channel, index) |
| 11-63 | 53 | reserved | Reserved or extended parameters |

**EX3D Command Code Description**:

- Base command range: 0x80-0x94
- GET command format: `Base Command | 0x0100` (set 9th bit)
- Supported GET commands:
  - 0x180: CMD_CH_NUM (Get Channel Count)
  - 0x182: CMD_ONOFF (Get EX3D Switch)
  - 0x183: CMD_ANGLE (Get Angle)
  - 0x184: CMD_SOUND_FIELD (Get Sound Field)
  - 0x185: CMD_MUTE (Get Mute)
  - 0x186: CMD_ON_GAIN (Get On Gain)
  - 0x187: CMD_LMT_THRESHOLD (Get Limiter Threshold)
  - 0x188: CMD_UPMIX (Get Upmix)
  - 0x189: CMD_LFE (Get LFE Gain)
  - 0x18A: CMD_OFF_GAIN (Get Off Gain)
  - 0x18B: CMD_SOUND_FIELD_NUM (Get Sound Field Count)
  - 0x18C: CMD_SOUND_FIELD_NAME (Get Sound Field Name)
  - 0x18D: CMD_LEVEL (Get Level)
  - 0x18E: CMD_LMT_ATTACKK_TIME (Get Limiter Attack Time)
  - 0x18F: CMD_LMT_RELEASE_TIME (Get Limiter Release Time)
  - 0x193: CMD_EXPAND_GAIN (Get Expand Gain)
  - 0x194: CMD_REDUCE_GAIN (Get Reduce Gain)

**Device Processing**:

- Parses EX3D command code, extracts base command and parameters
- Calls corresponding EX3D handler (hid_receive_task_in_c)
- Returns current parameter value

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0xB1 (echo) |
| 3-6 | 4 | ex3d_cmd | EX3D command code (echo) |
| 7-10 | 4 | result1 | Result 1 (depends on command) |
| 11-14 | 4 | result2 | Result 2 (some commands need multiple results, e.g. angle, multi-channel data) |
| 15-18 | 4 | result3 | Result 3 (extended result, e.g. multi-channel data) |
| 19-63 | 45 | reserved | Other results or padding (max 14 uint32 values, total < 63 bytes) |

**Return Value Description**:

- Return value count and format depend on specific EX3D command
- Single value command: returns 1 uint32
- Multi-value command (e.g. angle): returns multiple uint32
- String command (e.g. sound field name): first returns length (uint32), then string data
- For detailed return formats, refer to ex3d_protocol.md

**Usage Instructions**:

- This command unifies all EX3D reading commands
- Parameter format consistent with original EX3D protocol
- For detailed EX3D command descriptions, refer to ex3d_protocol.md

#### 2.2.34 Set Sampling Rate Upsampling (0x80)

**Function**: Set device sampling rate upsampling switch

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x80 |
| 3 | 1 | upsample | Upsample status (0=Disable, 1=Enable) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

**Parameter Description**:

- Upsample status: 0=Disable upsampling, 1=Enable upsampling

**Return Value**:

No direct return value. To confirm upsampling status, use GET_UPSAMPLE (0x81).

#### 2.2.35 Get Sampling Rate Upsampling (0x81)

**Function**: Read device current sampling rate upsampling status

**Request Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x81 |
| 3-63 | 61 | reserved | Reserved fields (fill with 0) |

**Response Format (64 bytes)**:

| Offset | Length | Field Name | Description |
|:----:|:----:|:------:|:----:|
| 0 | 1 | report_id | Fixed value: 0x01 |
| 1 | 1 | sync_header | Sync header: 0x77 |
| 2 | 1 | cmd_header | Command header: 0x81 (echo) |
| 3 | 1 | upsample | Current upsample status (0=Disabled, 1=Enabled) |
| 4-63 | 60 | reserved | Reserved fields (fill with 0) |

## 3. Data Flow and Timing :material-timeline-clock:

### 3.1 Typical Operation Flows

#### 3.1.1 Mode Switching Flow
1. GUI sends SET_EQ_MODE command (0x8A)
2. Device updates internal mode state
3. GUI sends GET_EQ_MODE command (0x8B) for confirmation
4. Device responds with current mode state

#### 3.1.2 Parameter Setting Flow
1. GUI sends SET_EQ_MODE command to switch to target mode (0x8A)
2. Send commands for all 8 filters sequentially (0x8D)
3. Device receives and updates internal parameter cache
4. Optional: Send GET_EQ_PARAMS command to verify parameters (0x8E)

#### 3.1.3 Parameter Reading Flow
1. GUI sends SET_EQ_MODE command to switch to target mode (0x8A)
2. GUI sends GET_EQ_PARAMS request (0x8E)
3. Device prepares response data
4. GUI reads response

### 3.2 Timing Requirements and Constraints

!!! warning "Timing Requirements"
    - **Command Interval**: Minimum 5ms recommended
    - **Read Delay**: Wait 100ms after sending read request
    - **Mode Switching**: Wait for device internal state to stabilize after completion

!!! danger "Protocol Limitations and Constraints"
    **Hardware Limitations**

    - **Filter Count**: Fixed at 8 filters (MAX_EQ_BANDS = 8)
    - **Mode Count**: Supports 10 modes (0-9). Mode meanings are defined by firmware.
    - **Sample Rate Support**: 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz (device capability, independent of protocol fields)

    **Parameter Ranges**

    | Parameter | Range | Format |
    |:----:|:----:|:----:|
    | Center frequency (freq) | 20Hz - 20kHz | float (little endian) |
    | Q value (q) | 0.1 - 30.0 | float (little endian) |
    | Bandwidth (bw) | 1Hz - 20kHz | float (little endian) |
    | Gain (gain) | -24dB - +24dB | float (little endian) |
    | Overall gain (mode gain) | -50dB - 0dB | int32 (little endian) |

## 4. Preset Mode Definitions :material-equalizer:

### 4.1 Mode Classification

| Mode Index | Mode Name | Description | Type |
|:--------:|:--------:|:--------:|:----:|
| 0 | JAZZ | Jazz music optimization | Preset Mode |
| 1 | POP | Pop music optimization | Preset Mode |
| 2 | ROCK | Rock music optimization | Preset Mode |
| 3 | ClASIC | Classical music optimization | Preset Mode |
| 4 | R&B | Rhythm & blues optimization | Preset Mode |
| 5 | 3A Game | AAA game audio optimization | Preset Mode |
| 6 | FPS | FPS game audio optimization | Preset Mode |
| 7 | User 1 | User-defined mode 1 | User Mode |
| 8 | User 2 | User-defined mode 2 | User Mode |
| 9 | User 3 | User-defined mode 3 | User Mode |

!!! info "Mode Characteristics"
    - **Preset Modes**: Factory presets, non-modifiable, optimized for specific music genres
    - **User Modes**: Support user-defined parameters, can be saved and reset

---

## 5. Key Features :material-star:

### 5.1 Device-Side Coefficient Calculation

- The host only sends parameters (`freq`/`q`/`bw`/`gain`)
- The device calculates filter coefficients in real time based on the parameters

### 5.2 Parameter Formats

- Floating-point parameters: `freq`, `q`, `bw`, `gain` use IEEE 754 `float` (Little Endian)
- Overall gain: `int32` (Little Endian, range `-50dB ~ 0dB`)

### 5.3 Error Handling

- Packet length validation
- Sync header validation
- Parameter range validation
- Filter index boundary validation

### 5.4 Mode Management

- Supports EQ mode switching and saving
- After switching modes, it is recommended to read back state for synchronization

## 6. Notes :material-alert:

1. **Timing Requirements**: After sending parameters, wait for device processing before sending the next command
2. **Data Completeness**: All 8 filters’ parameters should be sent, even if some filters are unused
3. **Mode Synchronization**: After setting a mode, call the read-mode command to ensure synchronization
4. **Error Recovery**: If communication fails, reconnect and retry
5. **Parameter Validation**: Device validates parameter ranges; out-of-range values are clamped or rejected

---

## Consultation and Feedback

<details>
<summary>Click to expand consultation and feedback form</summary>

--8<-- "common/customer_form.md"

</details>