XMOS XU316 HiFi USB Decoder ZeroCode Firmware Configuration Protocol¶

I. 💡 ZeroCode Firmware Functional Scope¶

• The firmware focuses exclusively on audio-related functions and does not handle buttons, indicators, or other functions unrelated to core functionality.
• Other user interaction features are managed by the MCU.
• MCU and XU316 communicate bidirectionally via UART for command and data exchange.
• The firmware communicates with the computer via HID.

II. XU316 and MCU Configuration Protocol¶

1. Low-Level Protocol¶

Based on UART (Universal Asynchronous Receiver/Transmitter) protocol

Terminology¶

2. Frame Format¶

Notes All multi-byte data is transmitted in big-endian format. Examples in the protocol are in hexadecimal.

3. XU316 Startup Sequence and MCU Interaction Process¶

3.1 Power-on Startup and Startup Options Phase (Only runs during manual power-on startup)¶

Steps:

1. XU316 startup sends a start command (command 0x00) to the MCU, including UAC1.0 VID/PID, UAC2.0 VID/PID, basic information CRC, and power-on configuration CRC.
2. MCU receives the startup command, checks whether basic information and power-on configuration need to be updated, and sends the corresponding response to XU316. XU316 waits for MCU to respond to startup for up to 3 seconds.
3. If no response is received within 300ms, XU316 resends the startup command up to 4 times. If no response is received after 4 attempts, it loads the default USB configuration and enumerates USB.
4. MCU responds to the startup command to XU316, including startup options.
5. XU316 parses the startup options.

3.2 Basic Information Update Phase (Only runs during manual power-on startup)¶

Condition: Startup options include 0x01 (Update basic product information)

1. XU316 requests to read basic product information, sends command 0x01
2. MCU returns new basic product information to XU316.
3. XU316 updates and saves the configuration.

3.3 Power-on Configuration Acquisition Phase (Only runs during manual power-on startup)¶

Condition: Startup options include 0x02 (Update power-on configuration) or data read from Flash is incomplete.

1. XU316 requests to get power-on configuration. Sends command 0x02
2. MCU returns new power-on configuration to XU316.
3. XU316 updates and saves the configuration.

3.4 Loading Application Firmware Phase¶

Steps:

1. XU316 gets the current mode, sends command 0x03.
2. MCU returns the current mode to XU316.
3. XU316 loads the corresponding mode based on the current mode.

APP Running Phase¶

Steps:

1. XU316 gets the current user configuration (volume, etc.), command 0x04.
2. MCU returns the current user configuration to XU316.
3. XU316 initializes the APP and applies the current user configuration.
4. XU316 sends a startup completion command to MCU, command 0x05.
5. MCU returns a completion command response to XU316.

4. Command List¶

Notes:

1. All commands must follow the basic frame format
2. Some commands require confirmation response from the other party
3. Certain commands can only be used under specific conditions (such as OTA-related commands)
4. Command response timeout is typically 5 seconds
5. Application commands should be sent only after XU316 startup commands are completed

5. Protocol Mechanism¶

5.1 Confirmation Mechanism¶

• All commands require a confirmation reply from the other party
• Default command timeout is 5 seconds, after which it's considered failed, unless otherwise specified

6. Business Protocol¶

6.1 Basic Function Commands¶

6.1.1 Start Startup (Command: 0x00)¶

XU316 Sends:¶

MCU Response Field Description¶

6.1.2 Read Product Information (Command: 0x01)¶

XU316 Sends¶

MCU Response¶

6.1.3 Read Power-on Configuration Information (Command: 0x02)¶

XU316 Sends¶

MCU Response¶

6.1.4 Get Current Audio Mode (Command: 0x03)¶

XU316 Sends¶

MCU Response¶

6.1.5 Get Current User Configuration (Command: 0x04)¶

XU316 Sends¶

MCU Response¶

6.1.6 Startup Completion Command (Command: 0x05)¶

XU316 Sends¶

MCU Response¶

6.2 Business Control and Query Commands (Can only be sent after startup is complete)¶

6.2.1 Report Application Status (Command: 0x20)¶

XU316 Sends¶

MCU Response¶

6.2.2 Media Control (Command: 0x21)¶

MCU Sends¶

XU316 Response¶

6.2.3 Set Playback Audio Stream Format and Type (Command: 0x22)¶

XU316 Sends¶

MCU Response¶

6.2.4 Set Audio Mode (Command: 0x23)¶

MCU Sends¶

XU316 Response¶

6.2.5 Send Playback Volume (Command: 0x24)¶

XU316 Sends¶

MCU Response¶

6.2.6 Send Recording Volume (Command: 0x25)¶

XU316 Sends¶

MCU Response¶

6.3 MCU OTA Upgrade Commands (Pass-through Mode)¶

6.3.1 HID Start MCU OTA Upgrade Command¶

XU316 Sends: (HID Report ID1 Output Report 40 bytes)¶

MCU Response¶

6.3.2 HID Send MCU Upgrade Data Packet¶

XU316 Sends¶

MCU Response¶

6.3.3 HID Send MCU Upgrade End Packet¶

XU316 Sends¶

MCU Response¶

7. Business Information¶

7.1 Basic Product Information¶

The MCU can determine whether to update the basic product information based on the CRC returned by the XU316.

7.2 Power-on Configuration Information¶

The MCU can determine whether to update the power-on configuration information based on the CRC returned by the XU316.

7.3 Application Running Parameters¶

7.4 User Configuration Parameters¶

8. Data Field Description¶

8.1 Restart Reason¶

8.2 Startup Options¶

8.3 Audio Mode¶

8.4 Microphone Volume¶

8.5 DAC Volume¶

8.6 Power-on Mode¶

8.7 Media Control (Media Buttons)¶

8.8 Audio Stream Format and Type¶

Audio Stream Format¶

Audio Type¶