XU316 USB HiFi Decoder Zero-Code Product Configuration Protocol¶

Jointly Supported
XMOS Official Website: www.xmos.com
Phaten Audio Solutions Official Website: www.phaten-audio.com

Protocol Overview ¶

Functional Scope and Purpose

This document provides detailed specifications for the UART-based configuration protocol between XU316 USB HiFi Decoder zero-code products and MCU. The protocol offers a complete feature set for audio device configuration, status monitoring, and media control.

1. Protocol Foundation Specification ¶

1.1 Underlying Communication Protocol¶

Based on UART (Universal Asynchronous Receiver/Transmitter) Protocol

Parameter	Value
Baud Rate	115200 bps
Data Bits	8
Parity	None
Stop Bits	1
Flow Control	None

1.2 Frame Format and Data Transmission¶

General Frame Format

All commands and responses follow this frame format:

Field	Byte Count	Description
Frame Header	2	Fixed as 0x55aa
Version	1	Protocol version number
Command	1	Indicates frame function
Data Length	1	Length N of subsequent data, excluding final checksum byte
Data	N	Specific data content
Checksum	1	Sum of all bytes from frame header, modulo 256

Data Transmission Notes

All multi-byte data is transmitted in Big Endian mode. All example data in the protocol is shown in hexadecimal format.

1.3 Communication Mechanism¶

1.3.1 Acknowledgment Mechanism¶

Acknowledgment and Timeout Handling

All commands require response acknowledgment from the recipient
Default command timeout is 300ms, timeout indicates communication failure
Special commands may have different timeout values, specified in respective command descriptions

1.3.2 Retry and Fault Tolerance Mechanism¶

flowchart TD
    A[Send Command] --> B{Wait for Response}
    B -->|Timeout| C[Resend Command]
    C --> D{Retry Count<4?}
    D -->|Yes| B
    D -->|No| E[Use Default Configuration]
    B -->|Response Received| F[Process Response]

2. Device Startup and Initialization ¶

2.1 Startup Interaction Flow¶

sequenceDiagram
    participant XU316
    participant MCU
    participant Flash

    rect
        Note over XU316,Flash: System Loader Firmware


        rect
            Note over XU316,MCU: Power-On Startup Phase
            XU316->>MCU: Send start-up command (0x00)
            Note over XU316:
            alt Timeout with no response (max 4 attempts, if all fail enter USB->I2S mode directly)
                XU316->>MCU: Resend start-up command (0x00)
            end
            MCU-->>XU316: Return startup options
            Note over XU316: Parse startup options
        end

        rect
            Note over XU316,Flash: Basic Information Update Phase
            alt Startup option does not include 0x01 (do not update basic product info)
                XU316->>Flash: Read basic product info
                Flash-->>XU316: Return basic product info
            else Startup option includes 0x01 (update basic product info) or Flash data incomplete
                XU316->>MCU: Send read basic product info command (0x01)
                MCU-->>XU316: Return new basic product info
                XU316->>Flash: Save configuration
            end
        end

        rect
            Note over XU316,Flash: Power-On Configuration Retrieval Phase
            alt Startup option does not include 0x02 (do not update power-on config)
                XU316->>Flash: Read power-on configuration
                Flash-->>XU316: Return power-on configuration data
            else Startup option includes 0x02 (update power-on config) or Flash data incomplete
                XU316->>MCU: Send get power-on config command (0x02)
                MCU-->>XU316: Return new power-on config
                XU316->>Flash: Save new power-on config
            end
        end

        rect
            Note over XU316: Loading Application Mode Phase
            XU316->>MCU: Send get current mode command (0x03)
            MCU-->>XU316: Return current mode
            Note over XU316: Load corresponding mode based on current mode
         end

    end

    rect
        Note over XU316,MCU: APP Running Phase
        XU316->>MCU: Get current user config command (0x04)
        MCU-->>XU316: Return current user config
        Note over XU316: Initialize APP and apply current user config
        XU316->>MCU: Send startup complete command (0x05)
        MCU-->>XU316: Return completion command response
        par Parallel Processing
            loop Status Reporting
                XU316->>MCU: Status change or 15s timer send
            end
            loop Business Processing
                MCU->>XU316: Send business commands
                XU316-->>MCU: Respond to business commands
            end
        end
    end

2.2 Detailed Startup Flow Description¶

Power-On Startup and Options PhaseBasic Information Update PhasePower-On Configuration Retrieval PhaseApplication Firmware Loading PhaseApplication Initialization Phase

XU316 sends start-up command (command 0x00) to MCU at startup, including:
- UAC1.0 VID/PID
- UAC2.0 VID/PID
- Basic info CRC
- Power-on config info CRC
MCU receives startup command, checks if info needs updating, and sends corresponding reply
XU316 waits for MCU response
If timeout with no response, XU316 resends startup command up to 4 times
If still no response, directly loads default USB configuration and enumerates USB
If normal response received, XU316 parses startup options

Execution Condition: Startup options include 0x01 (update basic product info)

Steps:

XU316 sends 0x01 command to request reading basic product info
MCU returns new basic product info to XU316
XU316 updates and saves configuration to internal storage

Execution Condition: Startup options include 0x02 (update power-on config) or Flash data is incomplete

Steps:

XU316 sends 0x02 command to request getting power-on configuration
MCU returns new power-on configuration to XU316
XU316 updates and saves configuration to internal storage

Steps:

XU316 sends 0x03 command to get current input/output mode
MCU returns current mode info to XU316
XU316 loads corresponding input/output mode based on returned mode

Steps:

XU316 sends 0x04 command to get current user configuration
MCU returns current user configuration to XU316
XU316 initializes application and applies related configuration
XU316 sends 0x05 command to indicate startup complete
MCU returns confirmation response

3. Protocol Command Set ¶

3.1 Command Classification Overview¶

Startup and Basic Commands (0x00-0x0F)Business Control Commands (0x20-0x2F)HID-MCU Passthrough Commands (0xEE-0xEF)DAC Control Commands (0xF0-0xFF)

Command	Command Description	Direction
0x00	Start-up	XU316→MCU
0x01	Read product info	XU316→MCU
0x02	Read power-on config info	XU316→MCU
0x03	Get current input/output mode	XU316→MCU
0x04	Get current user configuration	XU316→MCU
0x05	Startup complete command	XU316→MCU

Command	Command Description	Direction
0x20	Report application status	XU316→MCU
0x21	Media control	MCU→XU316
0x22	Report playback audio stream format and type	XU316→MCU
0x23	Set input/output mode	MCU→XU316
0x24	XU316 send playback volume	XU316→MCU
0x25	Send recording volume	XU316→MCU
0x26	Switch MCLK	MCU→XU316

Command	Command Description	Direction
0xEE	HID-initiated command passed through XU316 to MCU	XU316→MCU

Command	Command Description	Direction
0xF0	DAC configuration selection command	MCU→XU316

Command Usage Instructions

All commands must follow basic frame format specification
Each command requires recipient acknowledgment for successful execution
Business control commands (0x20 and above) can only be used after device startup complete

3.2 Basic Function Command Details¶

3.2.1 Start-up (0x00)¶

Command FormatFunction DescriptionUsage FlowNotes

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x00
Data Length:   1 byte  - 17
Data:         17 bytes
              B0:     Restart reason (0x00 power-on restart, 0x01 mode switch restart, 0xFF other reason)
              B1-2:   USB Vendor ID (UAC1.0)
              B3-4:   USB Product ID (UAC1.0)
              B5-6:   USB Vendor ID (UAC2.0)
              B7-8:   USB Product ID (UAC2.0)
              B9-12:  Basic info 32-bit CRC
              B13-16: Power-on config info 32-bit CRC
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x00
Data Length:   1 byte  - 0x1
Data:          1 byte
              B0: Startup options
                  0x00 Use all default info
                  0x01 Need to update basic product info
                  0x02 Need to update power-on config info
                  0x04 Need to update other config info
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is sent first by XU316 after power-on or restart to notify MCU that device has started
XU316 sends currently stored product info CRC and config info CRC to MCU
MCU compares CRC to determine if XU316 config info needs updating
MCU notifies XU316 of subsequent operations to execute through startup options field in response

flowchart TB
    A[XU316 Startup] -->B[Send 0x00 Command]
    B -->C{MCU Response}
    C -->|Timeout| D[Resend Command]
    D -->E{Retry Count<4?}
    E -->|Yes| C
    E -->|No| F[Use Default Configuration]
    C -->|Normal Response| G[Parse Startup Options]
    G -->|0x01| H[Update Basic Product Info]
    G -->|0x02| I[Update Power-On Config Info]
    G -->|0x04| J[Update Other Config Info]
    G -->|0x00| K[Continue Startup Flow]

If MCU has no response, XU316 will use stored default configuration to continue startup
Restart reason field can be used by MCU to identify specific reason for XU316 restart for different handling
When multiple info items need updating, MCU can combine multiple options through bit operations

3.2.2 Read Product Info (0x01)¶

Command FormatFunction DescriptionData Structure

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x01
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x01
Data Length:   1 byte  - 0x3C (60 bytes)
Data:         60 bytes - Product basic info, see data field description
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 to get basic product info such as VID/PID, product name, etc.
Execution condition: Startup options include 0x01 flag or product info CRC mismatch
After receiving this info, XU316 will update internally stored product basic info

Product basic info data structure (60 bytes):

VID1 (UAC1.0):        2 bytes
PID1 (UAC1.0):        2 bytes
VID2 (UAC2.0):        2 bytes
PID2 (UAC2.0):        2 bytes
ManufactureName:     16 bytes (string)
ProductName:         16 bytes (string)
SerialNumber:        16 bytes (string)
CRC:                  4 bytes (32-bit CRC checksum)

3.2.3 Read Power-On Config Info (0x02)¶

Command FormatFunction DescriptionData Structure

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x02
Data Length:   1 byte  - 0x00
Data:          0 bytes - No data
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x02
Data Length:   1 byte  - 0x0E (14 bytes)
Data:         14 bytes - Power-on config info, see section 4.1-Power-On Config Info
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 to get initial power-on configuration info
Execution condition: Startup options include 0x02 flag or power-on config CRC mismatch
XU316 will set default input/output mode, volume and other parameters based on this config info

Power-on config info data structure (14 bytes):

Default input/output mode:       5 bytes
Mute time:                       2 bytes (0-65535ms)
Microphone default volume:       1 byte
DAC left channel default volume: 1 byte
DAC right channel default volume:1 byte
CRC:                             4 bytes (32-bit CRC checksum)

3.2.4 Get Current Input/Output Mode (0x03)¶

Command FormatFunction Description

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x03
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x03
Data Length:   1 byte  - 0x05 (5 bytes)
Data:          5 bytes - Input/output mode, see data field section
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 at startup to query currently enabled input/output mode
XU316 will load corresponding application firmware based on returned mode
This command is used for mode matching and confirmation during device startup

3.2.5 Get Current User Configuration (0x04)¶

Command FormatFunction Description

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x04
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x04
Data Length:   1 byte  - 0xE (14 bytes)
Data:         14 bytes - User config parameters, see section 4.1-User Config Parameters
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 to get currently user-selected volume, mode and other configurations
Executed after application firmware loaded, before application startup
Application will initialize corresponding parameters based on returned info

3.2.6 Startup Complete Command (0x05)¶

Command FormatFunction Description

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x05
Data Length:   1 byte  - N
Data:          N bytes
              B0: Startup status (0 startup success, 1 mode mismatch, other values startup failure)
              B1-BN: Application runtime parameters, see section 4.1-Application Runtime Parameters
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x05
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command indicates XU316 startup flow has completed and can begin normal operation
Contains startup status info to notify MCU if startup succeeded or encountered problems
All subsequent business commands can only be used after this command is successfully sent

3.3 Business Control Command Details¶

Usage Prerequisites

The following commands can only be used after XU316 startup complete (after sending 0x05 command and receiving response)

3.3.1 Report Application Status (0x20)¶

Command FormatFunction Description

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x20
Data Length:   1 byte  - N
Data:          N bytes - Application runtime parameters, see section 4.1-Application Runtime Parameters
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x20
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 to report current application status to MCU
Typically sent when status changes, such as volume change, mode switch, etc.
MCU can update UI display or adjust related functions based on this info

3.3.2 Media Control (0x21)¶

Command FormatFunction DescriptionControl Button Mapping Table

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x21
Data Length:   1 byte  - 0x01 (1 byte)
Data:          1 byte  - Media control command
              0x00 Volume Up / Vol Up
              0x01 Volume Down / Vol Down
              0x02 Play/Pause / PLAY/PAUSE
              0x03 Next Track / NEXT
              0x04 Previous Track / PREV
              0x05 Fast Forward / FORWARD
              0x06 Rewind / REWIND
              0x07 Mute / MUTE
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x21
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by MCU to send media control commands to XU316
After receiving command, XU316 will convert to corresponding HID command and send to computer
Suitable for implementing remote control or physical button control of media playback

Control Code	Function	USB HID Usage
0x00	Volume Up	Increase system volume
0x01	Volume Down	Decrease system volume
0x02	Play/Pause	Control media playback state
0x03	Next Track	Switch to next song
0x04	Previous Track	Switch to previous song
0x05	Fast Forward	Fast forward in current track
0x06	Rewind	Rewind in current track
0x07	Mute	Toggle system mute state

3.3.3 Report Playback Audio Stream Format and Type (0x22)¶

Command FormatFunction Description

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x22
Data Length:   1 byte  - 0x02 (2 bytes)
Data:          2 bytes - Audio stream format and type, see audio stream format and type field
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x22
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 to report current audio stream format and type to MCU
Typically sent when playback starts or format changes
MCU can update display based on this info, such as showing PCM/DSD/MQA/DOP status

3.3.4 Set Input/Output Mode (0x23)¶

Command FormatFunction Description

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x23
Data Length:   1 byte  - 0x05 (5 bytes)
Data:          5 bytes - Input/output mode, see input/output mode field
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x23
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by MCU to request XU316 switch to specific input/output mode
Typically triggered by user operation, such as pressing mode selection button
XU316 may need to restart to load new mode firmware

3.3.5 Send Playback Volume (0x24)¶

Command FormatFunction Description

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x24
Data Length:   1 byte  - 0x02 (2 bytes)
Data:          2 bytes
              Byte 1: Left channel (0xFF Mute, 0-0dB, -127: -127dB)
              Byte 2: Right channel (0xFF Mute, 0-0dB, -127: -127dB)
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x24
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 to report current playback volume to MCU

3.3.6 Send Recording Volume (0x25)¶

Command FormatFunction Description

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x25
Data Length:   1 byte  - 0x01 (1 byte)
Data:          1 byte  - 0xFF Mute, 0-0dB -127: -127dB
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x25
Data Length:   1 byte  - 0x00
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 to report current microphone recording volume to MCU
Reserved command, currently not used

3.3.7 Switch MCLK (0x26)¶

Command FormatFunction Description

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x26
Data Length:   1 byte  - 1
Data:          1 byte  - 0: Internal MCLK, 1: External MCLK
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x26
Data Length:   1 byte  - 0
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used by XU316 to control switching master clock source
Can switch between using internal clock or external clock
Important for certain audio application scenarios requiring precise synchronization

3.3.8 Set Unmute (0x27)¶

Command FormatFunction Description

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x27
Data Length:   1 byte  - 2
Data:          2 bytes -
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x27
Data Length:   1 byte  - 0
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

DAC unmute time delay during mode switching, unit is milliseconds

3.3.9 Send Audio Format Time Delay (0x28)¶

Command FormatFunction Description

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0x28
Data Length:   1 byte  - 2
Data:          2 bytes -
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0x28
Data Length:   1 byte  - 0
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

Send audio format time delay

3.3.10 Get Firmware Version Command (0xF1)¶

Command FormatFunction Description

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0xF1
Data Length:   1 byte  - 2
Data:          2 bytes -
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0xF1
Data Length:   1 byte  - 0
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

Get firmware version

3.4 DAC Configuration Selection (0xF0)¶

Command FormatFunction Description

MCU Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0xF0
Data Length:   1 byte  - 4
Data:          4 bytes
              Byte 0: 0: Enable I2C DAC configuration  1: Disable I2C DAC configuration
              Byte 1 - 3: reserved
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

XU316 Returns

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0xF0
Data Length:   1 byte  - 0
Data:          0 bytes
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

Test command for MCU to set DAC configuration selection in XU316. Let XU316 configure DAC via DAC I2C or MCU configure DAC itself
This command is product-specific and not supported by all products. Please refer to product specification for support details.

3.5 HID and MCU Data Passthrough Commands via XU316¶

3.5.1 HID Passthrough Data to MCU via XU316 (0xEE)¶

Command FormatFunction Description

XU316 Sends

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x00
Command:       1 byte  - 0xEE
Data Length:   1 byte  - 0x39 (57 bytes), due to HID protocol limitation, data length must be 57 bytes
Data:         57 bytes - Due to HID protocol limitation, must be 57 bytes passthrough data
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

MCU Returns (can return multiple frames)

Frame Header:  2 bytes - 0x55aa
Version:       1 byte  - 0x03
Command:       1 byte  - 0xEE
Data Length:   1 byte  - 0x39 (57 bytes), due to HID protocol limitation, data length must be 57 bytes
Data:         57 bytes - Due to HID protocol limitation, must be 57 bytes passthrough data
Checksum:      1 byte  - Sum of all bytes from frame header, modulo 256

This command is used for HID-initiated passthrough data to MCU via XU316
Generally passthrough data is MCU OTA data or MCU data reply to HID

4. Data Structure Definitions ¶

4.1 Product Configuration Data Structures¶

1. Product Basic Info2. Power-On Config Info3. Application Runtime Parameters4. User Config Parameters

Field	Byte Count	Description
VID1	2	USB Vendor ID (UAC1.0)
PID1	2	USB Product ID (UAC1.0)
VID2	2	USB Vendor ID (UAC2.0)
PID2	2	USB Product ID (UAC2.0)
ManufactureName	16	USB Manufacture Name (string, max 16 bytes)
ProductName	16	USB Product Name (string, max 16 bytes)
SerialNumber	16	Product Serial Number (string, max 16 bytes)
CRC	4	32-bit CRC checksum calculated for all fields

CRC Usage Notes

MCU can determine if product basic info needs updating based on CRC value returned by XU316. When CRC mismatch occurs, should send complete product basic info.

Field	Byte Count	Description
Default input/output mode	5	See input/output mode field description
Mute time	2	0-65535 (ms)
Microphone default volume	1	See microphone volume field description
DAC left channel default volume	1	See DAC volume field description
DAC right channel default volume	1	See DAC volume field description
CRC	4	32-bit CRC checksum calculated for all fields

Field	Byte Count	Description
Input/output mode	5	See input/output mode field description
Mute time	2	0-65535 (ms)
Microphone volume	1	See microphone volume field description
DAC left channel volume	1	See DAC volume field description
DAC right channel volume	1	See DAC volume field description
CRC	4	32-bit CRC checksum calculated for all fields

Field	Byte Count	Description
Input/output mode	5	See input/output mode field description
Mute time	2	0-65535 (ms)
Microphone volume	1	See microphone volume field description
DAC left channel volume	1	See DAC volume field description
DAC right channel volume	1	See DAC volume field description
CRC	4	32-bit CRC checksum calculated for all fields

4.2 Input/Output Mode Data Format¶

Bit Field Definitions

Byte	Function Description
BYTE 0-BYTE4	Specific value definitions refer to product specification

4.3 Control Parameter Data Formats¶

Restart ReasonPower-On ModeVolume Control ParametersAudio Stream FormatAudio Type

Value	Description
0x00	Power-on restart
0x01	Mode switch restart
0xFF	Other reason restart

Value	Description
0x00	Default mode, use power-on config info parameters at startup
0x01	Power-off memory mode, use user config parameters from MCU at startup

Microphone Volume

Value	Description
0xFF	Mute
0x00-0xFE	Volume value, specific mapping defined by application

DAC Volume

Value	Description
0x00	Mute
0x01-0xFF	Volume value, specific mapping defined by application

Value	Format	Parameters
0x00	AUDIO_PCM_44100	44.1kHz PCM
0x01	AUDIO_PCM_48000	48kHz PCM
0x02	AUDIO_PCM_88200	88.2kHz PCM
0x03	AUDIO_PCM_96000	96kHz PCM
0x04	AUDIO_PCM_176400	176.4kHz PCM
0x05	AUDIO_PCM_192000	192kHz PCM
0x06	AUDIO_PCM_352800	352.8kHz PCM
0x07	AUDIO_PCM_384000	384kHz PCM
0x08	AUDIO_PCM_705600	705.6kHz PCM
0x09	AUDIO_PCM_768000	768kHz PCM
0x0A	AUDIO_PCM_1441200	1.4112MHz PCM
0x0B	AUDIO_PCM_1536000	1.536MHz PCM
0x0C	AUDIO_PCM_32000	32kHz PCM
0x0D	AUDIO_PCM_64000	64kHz PCM
0x0E	AUDIO_PCM_128000	128kHz PCM
0x0F	AUDIO_PCM_256000	256kHz PCM
0x10	AUDIO_PCM_512000	512kHz PCM
0x11	AUDIO_DSD_64	DSD64
0x12	AUDIO_DSD_128	DSD128
0x13	AUDIO_DSD_256	DSD256
0x14	AUDIO_DSD_512	DSD512
0x15	AUDIO_DSD_1024	DSD1024
0x16	AUDIO_MQA_44100	44.1kHz MQA
0x17	AUDIO_MQA_88200	88.2kHz MQA
0x18	AUDIO_MQA_176400	176.4kHz MQA
0x19	AUDIO_MQA_352800	352.8kHz MQA
0x1A	AUDIO_MQA_705600	705.6kHz MQA
0x1B	AUDIO_MQA_1411200	1.4112MHz MQA
0x1C	AUDIO_MQA_2822400	2.8224MHz MQA
0x1D	AUDIO_MQA_5644800	5.6448MHz MQA
0x1E	AUDIO_MQA_48000	48kHz MQA
0x1F	AUDIO_MQA_96000	96kHz MQA
0x20	AUDIO_MQA_192000	192kHz MQA
0x21	AUDIO_MQA_384000	384kHz MQA
0x22	AUDIO_MQA_768000	768kHz MQA
0x23	AUDIO_MQA_1536000	1.536MHz MQA
0x24	AUDIO_MQA_3072000	3.072MHz MQA
0x25	AUDIO_MQA_6144000	6.144MHz MQA
0xFF	AUDIO_NO_USED	Not used

Value	Type	Description
0x00	PCM	Standard PCM audio
0x01	DoP	Reserved
0x02	MQA	MQA encoded audio
0x03	MQB	MQB encoded audio
0x04	MQA_Studio	MQA Studio encoding
0x05	DSD Native	DSD encoded audio

5. Consultation and Feedback¶

Click to expand consultation and feedback form

XU316 USB HiFi Decoder Zero-Code Product Configuration Protocol¶

Protocol Overview ¶

1. Protocol Foundation Specification ¶

1.1 Underlying Communication Protocol¶

1.2 Frame Format and Data Transmission¶

1.3 Communication Mechanism¶

1.3.1 Acknowledgment Mechanism¶

1.3.2 Retry and Fault Tolerance Mechanism¶

2. Device Startup and Initialization ¶

2.1 Startup Interaction Flow¶

2.2 Detailed Startup Flow Description¶

3. Protocol Command Set ¶

3.1 Command Classification Overview¶

3.2 Basic Function Command Details¶

3.2.1 Start-up (0x00)¶

3.2.2 Read Product Info (0x01)¶

3.2.3 Read Power-On Config Info (0x02)¶

3.2.4 Get Current Input/Output Mode (0x03)¶

3.2.5 Get Current User Configuration (0x04)¶

3.2.6 Startup Complete Command (0x05)¶

3.3 Business Control Command Details¶

3.3.1 Report Application Status (0x20)¶

3.3.2 Media Control (0x21)¶

3.3.3 Report Playback Audio Stream Format and Type (0x22)¶

3.3.4 Set Input/Output Mode (0x23)¶

3.3.5 Send Playback Volume (0x24)¶

3.3.6 Send Recording Volume (0x25)¶

3.3.7 Switch MCLK (0x26)¶

3.3.8 Set Unmute (0x27)¶

3.3.9 Send Audio Format Time Delay (0x28)¶

3.3.10 Get Firmware Version Command (0xF1)¶

3.4 DAC Configuration Selection (0xF0)¶

3.5 HID and MCU Data Passthrough Commands via XU316¶

3.5.1 HID Passthrough Data to MCU via XU316 (0xEE)¶

4. Data Structure Definitions ¶

4.1 Product Configuration Data Structures¶

4.2 Input/Output Mode Data Format¶

4.3 Control Parameter Data Formats¶

5. Consultation and Feedback¶

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