This example demonstrates how to setup the USB block of an Infineon MCU using Segger's emUSB-device middleware to implement a USB audio device and HID audio playback control which then connects to the PC via the USB interface. The example uses FreeRTOS.
This code example shows how to use the Infineon MCU to enumerate a standard USB audio device and HID consumer control over the USB interface. The PC host sees the device as:
- Audio playback device
- Microphone/recording device
- Remote control handling volume, play/pause
The Infineon MCU device works as a bridge between the audio data streamed from the USB host and the I2S block, which connects to an audio codec. The audio codec outputs the audio data to a speaker or headphones. The same audio codec can input microphone data and stream to the Infineon MCU device, which bridges to the USB interface.
CAPSENSE™ buttons are used to play/pause and change the volume of the data streamed to the Infineon MCU device. Any press of CAPSENSE™ buttons is reported back to the host over USB HID consumer control.
Figure 1. Block diagram
Provide feedback on this code example.
- ModusToolbox™ v3.2 or later (tested with v3.2)
- Board support package (BSP) minimum required version: 4.0.0
- Programming language: C
- Associated parts: All PSoC™ 6 MCU parts
- GNU Arm® Embedded Compiler v11.3.1 (
GCC_ARM) - Default value ofTOOLCHAIN - Arm® Compiler v6.16 (
ARM) - IAR C/C++ Compiler v9.40.2 (
IAR)
- PSoC™ 6 Wi-Fi Bluetooth® Pioneer Kit (
CY8CKIT-062-WIFI-BT) – Default value ofTARGET - PSoC™ 62S2 Wi-Fi Bluetooth® Pioneer Kit (
CY8CKIT-062S2-43012) - PSoC™ 62S1 Wi-Fi Bluetooth® Pioneer Kit (
CYW9P62S1-43438EVB-01) - PSoC™ 62S1 Wi-Fi Bluetooth® Pioneer Kit (
CYW9P62S1-43012EVB-01) - PSoC™ 62S2 Evaluation Kit (
CY8CEVAL-062S2,CY8CEVAL-062S2-LAI-4373M2,CY8CEVAL-062S2-MUR-43439M2,CY8CEVAL-062S2-LAI-43439M2,CY8CEVAL-062S2-MUR-4373EM2,CY8CEVAL-062S2-MUR-4373M2,CY8CEVAL-062S2-CYW43022CUB)
This code example requires an external analog microphone/speaker headset connected to the AK4954A audio codec. You must connect the CY8CKIT-028-TFT shield to the Arduino header if you are using any of the pioneer kits.
Note: The PSoC™ 6 Bluetooth® LE Pioneer Kit (CY8CKIT-062-BLE) and the PSoC™ 6 Wi-Fi Bluetooth® Pioneer Kit (CY8CKIT-062-WIFI-BT) ship with KitProg2 installed. ModusToolbox™ requires KitProg3. Before using this code example, make sure that the board is upgraded to KitProg3. The tool and instructions are available in the Firmware Loader GitHub repository. If you do not upgrade, you will see an error like "unable to find CMSIS-DAP device" or "KitProg firmware is out of date".
See the ModusToolbox™ tools package installation guide for information about installing and configuring the tools package.
This example uses the Audacity tool to record and play sound. You can also use any software tool that plays music.
The ModusToolbox™ tools package provides the Project Creator as both a GUI tool and a command line tool.
Use Project Creator GUI
-
Open the Project Creator GUI tool.
There are several ways to do this, including launching it from the dashboard or from inside the Eclipse IDE. For more details, see the Project Creator user guide (locally available at {ModusToolbox™ install directory}/tools_{version}/project-creator/docs/project-creator.pdf).
-
On the Choose Board Support Package (BSP) page, select a kit supported by this code example. See Supported kits.
Note: To use this code example for a kit not listed here, you may need to update the source files. If the kit does not have the required resources, the application may not work.
-
On the Select Application page:
a. Select the Applications(s) Root Path and the Target IDE.
Note: Depending on how you open the Project Creator tool, these fields may be pre-selected for you.
b. Select this code example from the list by enabling its check box.
Note: You can narrow the list of displayed examples by typing in the filter box.
c. (Optional) Change the suggested New Application Name and New BSP Name.
d. Click Create to complete the application creation process.
Use Project Creator CLI
The 'project-creator-cli' tool can be used to create applications from a CLI terminal or from within batch files or shell scripts. This tool is available in the {ModusToolbox™ install directory}/tools_{version}/project-creator/ directory.
Use a CLI terminal to invoke the 'project-creator-cli' tool. On Windows, use the command-line 'modus-shell' program provided in the ModusToolbox™ installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox™ tools. You can access it by typing "modus-shell" in the search box in the Windows menu. In Linux and macOS, you can use any terminal application.
The following example clones the "emUSB-Device: Audio device" application with the desired name "USBAudioDevice" configured for the CY8CKIT-062-WIFI-BT BSP into the specified working directory, C:/mtb_projects:
project-creator-cli --board-id CY8CKIT-062-WIFI-BT --app-id mtb-example-usb-device-audio-freertos --user-app-name USBAudioDevice --target-dir "C:/mtb_projects"
The 'project-creator-cli' tool has the following arguments:
| Argument | Description | Required/optional |
|---|---|---|
--board-id |
Defined in the field of the BSP manifest | Required |
--app-id |
Defined in the field of the CE manifest | Required |
--target-dir |
Specify the directory in which the application is to be created if you prefer not to use the default current working directory | Optional |
--user-app-name |
Specify the name of the application if you prefer to have a name other than the example's default name | Optional |
Note: The project-creator-cli tool uses the
git cloneandmake getlibscommands to fetch the repository and import the required libraries. For details, see the "Project creator tools" section of the ModusToolbox™ tools package user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).
After the project has been created, you can open it in your preferred development environment.
Eclipse IDE
If you opened the Project Creator tool from the included Eclipse IDE, the project will open in Eclipse automatically.
For more details, see the Eclipse IDE for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_ide_user_guide.pdf).
Visual Studio (VS) Code
Launch VS Code manually, and then open the generated {project-name}.code-workspace file located in the project directory.
For more details, see the Visual Studio Code for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_vscode_user_guide.pdf).
Keil µVision
Double-click the generated {project-name}.cprj file to launch the Keil µVision IDE.
For more details, see the Keil µVision for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_uvision_user_guide.pdf).
IAR Embedded Workbench
Open IAR Embedded Workbench manually, and create a new project. Then select the generated {project-name}.ipcf file located in the project directory.
For more details, see the IAR Embedded Workbench for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_iar_user_guide.pdf).
Command line
If you prefer to use the CLI, open the appropriate terminal, and navigate to the project directory. On Windows, use the command-line 'modus-shell' program; on Linux and macOS, you can use any terminal application. From there, you can run various make commands.
For more details, see the ModusToolbox™ tools package user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).
-
Connect the CY8CKIT-028-TFT shield to the Pioneer Kit.
-
Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.
-
Program the board using one of the following:
Using Eclipse IDE
-
Select the application project in the Project Explorer.
-
In the Quick Panel, scroll down, and click <Application Name> Program (KitProg3_MiniProg4).
In other IDEs
Follow the instructions in your preferred IDE.
Using CLI
From the terminal, execute the
make programcommand to build and program the application using the default toolchain to the default target. The default toolchain is specified in the application's Makefile but you can override this value manually:make program TOOLCHAIN=<toolchain>Example:
make program TOOLCHAIN=GCC_ARMAfter programming, the application starts automatically and confirm that the user LED turned on.
-
-
Connect a headphone or earphones to the audio jack of the CY8CKIT-028-TFT shield.
-
Connect another USB cable from your PC (or reuse the same cable used to program the kit) to the USB device connector (see the kit user guide for its location).
-
On the PC, verify that a new USB device is enumerated as a Speaker/Microphone and named as "emUSB Audio Device".
-
Use your audio software to specify the microphone or speaker. In the Audacity software tool, select the microphone and speaker name as "emUSB Audio Device".
-
Record some sound. In Audacity, press Record
. Stop at any time by pressing Stop 
. -
Press Play
to play the record and confirm that the sound is recorded correctly. -
Open a music player on the PC and play a song. Use the CAPSENSE™ slider to change the volume.
Note: You need to set the Speaker "emUSB Audio Device" as the default speaker device in your OS.
-
Press the left CAPSENSE™ button (BTN0) in the kit to play/pause a soundtrack.
You can debug the example to step through the code.
In Eclipse IDE
Use the <Application Name> Debug (KitProg3_MiniProg4) configuration in the Quick Panel. For details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ user guide.
Note: (Only while debugging) On the CM4 CPU, some code in
main()may execute before the debugger halts at the beginning ofmain(). This means that some code executes twice – once before the debugger stops execution, and again after the debugger resets the program counter to the beginning ofmain(). See KBA231071 to learn about this and for the workaround.
In other IDEs
Follow the instructions in your preferred IDE.
The CY8CKIT-028-TFT shield contains the audio codec AK4954A, which is a 32-bit stereo codec with a microphone.
If using AK4594A, the PSoC™ 6 MCU device configures the audio codec through the I2C Master (SCB) and streams the audio data through the I2S interface, which operates as Slave (Tx) and Master (Rx).
The codecs also require a Master clock (MCLK), which is generated by the PSoC™ 6 MCU device using a PWM (TCPWM). This clock is set to be 384x the frame rate. In this application, the frame rate can be set to 16 ksps and 22.05 ksps, requiring MCLK of 6.144 MHz and 8.4672 MHz, respectively. See the limitations section for more details.
Note that the recommended method to generate the MCLK is through the HFCLK4, which allows connecting directly to an external pin. In this case, the PLL can source the HFCLK1 (audio subsystem) and HFCLK4, and any other available clock can drive the HFCLK0 (system clock).
The firmware implements a bridge between the USB and I2S blocks. The emUSB descriptor implements the audio device class with three endpoints and the HID device class with one endpoint:
- Audio IN endpoint: Sends the audio data to the USB host
- Audio OUT endpoint: Receives the audio data from the USB host
- Audio Feedback endpoint: Controls the sample rate in the OUT endpoint
- HID audio/playback control endpoint: Controls the volume and audio play/ pause
The example project firmware uses FreeRTOS on the CM4 CPU. The following tasks are created in the main.c file:
-
Audio app task: Implements the high-level functions related to the audio. For example, requests to and volume.
-
Audio IN task: Implements the functions related to the audio IN Endpoint.
-
Audio OUT task: Implements the functions related to the audio OUT Endpoint.
-
Touch task: Implements the user interface related to CAPSENSE™.
-
Idle task: Goes to sleep.
Figure 2. Audio OUT and feedback endpoints flow
Figure 3. Audio IN endpoint flow
The Audio IN task waits for a recording request from the USB host. When it receives the request, it prepares I2S Rx to sample a new frame. It initially writes a null frame to the Audio IN Endpoint buffer to initiate the recording. The frame size depends on the sample rate (16 ksps), the number of channels (2x), and the duration of USB transfer (1 ms). The overall equation is:
Frame size = Sample rate x Number of channels x Transfer time
In this example, the frame size is equal to 16000 x 2 x 0.001 = 32 samples. Note that the Audio IN Endpoint Callback reads all the data available in the I2S Rx FIFO. In ideal conditions, it reads 32 samples, but it might read more or less samples, depending on the clock differences between the PSoC™ 6 MCU audio subsystem clock and the Host USB clock. Two additional samples are added on top of the frame size to define the maximum Audio IN and OUT endpoint size.
In the Touch task, the firmware uses the CAPSENSE™ resource to scan finger touches on the kit's buttons and slider. The left button (BTN0) plays or pauses a soundtrack. This is achieved by sending a command over the HID Audio/Playback Control endpoint. The CAPSENSE™ slider controls the volume. It also sends a command over the HID and configures the volume played in the audio codec.
The application has DMA enabled by default. Follow these steps to disable the DMA feature and ensure that the application functions without DMA:
- Remove the
USBD_ENABLE_DMAfrom the DEFINE variable in the Makefile. - Disable all DMA DataWire in the DMA tab from the device configurator.
- Turn off all DMA channel for endpoints in the USB personality from the device configurator.
- Disable the 'Enable DMA mode' in the USB personality from the device configurator.
A speaker and a microphone audio configuration must be defined by creating an “USB audio design” file (extension .uad). This file specifies all characteristics of the audio device and is converted by the USBAudioDeviceGenerator.exe tool into a C source file and a C header file, that should be used to build the audio application. The tool provided in emUSB-Device middleware library. For more details, see Section 17.2 from emUSB-Device User Guide & Reference Manual.
The /configs/speaker_mic_configs files contains the default audio configuration for the application and also provided the USB audio design file (speaker_mic_configs.uad).
The USB Audio Device Generator tool is a command line tool that can be invoked from a command shell:
USBAudioDeviceGenerator.exe [-s] [-o=<output-file>] <USB-audio-design-file>
-s = Silent execution (except for errors).
-o = Base name for the generated .c and .h files.
If not specified, the name of the USB audio design file is used.
This code example has the following limitations:
-
The maximum endpoint buffer size combined for all audio endpoints is limited to 192B. This code example supports sample rates of up to 16 ksps and 22.05 ksps because of this limitation.
Note: The clock configurations in the custom BSP provided in the templates folder support a 16 ksps sample rate.
Table 1. Project files
| File | Description |
|---|---|
| main.c (CM4) | Contains the main function, which is the entry point for executing the application. The main function sets up the user tasks and starts the RTOS scheduler. It also implements the Idle task. |
| audio_app.c/h | Contain the tasks that handles the audio-related blocks, such as the USB audio events and I2S control, handles recording requests to the Audio IN endpoint and handles playing requests to the Audio OUT endpoint. It also contain macros and functions related to the USB audio device class. |
| speaker_mic_configs.c/h | Contains a speaker and a microphone audio configuration generated by Seggers emUSBD Audio Device Generator tool. |
| touch.c/h | Handle CAPSENSE™ calls. |
| ak4954a.c/h | Implement the driver for the AK4954A audio codec. |
| rtos.h | Contains macros and handles for the FreeRTOS components in the application. |
| FreeRTOSConfig.h | Contains the FreeRTOS settings and configuration. Non-default settings are marked with inline comments. For details of FreeRTOS configuration options, see the FreeRTOS customization webpage. |
Table 2. Application resources
| Resource | Alias/object | Purpose |
|---|---|---|
| SCB (I2C) (HAL) | mi2c | I2C master driver to configure the audio codec |
| TCPWM (PWM) (HAL) | mclk_pwm | PWM to clock the external audio codec |
| USBDEV (HAL) | CYBSP_USBDEV | USB Device configured with Audio and HID Descriptors |
| I2S (HAL) | CYBSP_I2S | Interface with the audio codec |
| CAPSENSE™ (PDL) | CYBSP_CSD | Scan for button and slider touches |
| Resources | Links |
|---|---|
| Application notes | AN228571 – Getting started with PSoC™ 6 MCU on ModusToolbox™ AN215656 – PSoC™ 6 MCU: Dual-CPU system design |
| Code examples | Using ModusToolbox™ on GitHub |
| Device documentation | PSoC™ 6 MCU datasheets PSoC™ 6 technical reference manuals |
| Development kits | Select your kits from the evaluation board finder |
| Libraries on GitHub | mtb-pdl-cat1 – PSoC™ 6 Peripheral Driver Library (PDL) mtb-hal-cat1 – Hardware Abstraction Layer (HAL) library retarget-io – Utility library to retarget STDIO messages to a UART port |
| Middleware on GitHub | emUSB-Device – emUSB-Device emUSB-Device API reference – emUSB-Device API reference psoc6-middleware – Links to all PSoC™ 6 MCU middleware |
| Tools | ModusToolbox™ – ModusToolbox™ software is a collection of easy-to-use libraries and tools enabling rapid development with Infineon MCUs for applications ranging from wireless and cloud-connected systems, edge AI/ML, embedded sense and control, to wired USB connectivity using PSoC™ Industrial/IoT MCUs, AIROC™ Wi-Fi and Bluetooth® connectivity devices, XMC™ Industrial MCUs, and EZ-USB™/EZ-PD™ wired connectivity controllers. ModusToolbox™ incorporates a comprehensive set of BSPs, HAL, libraries, configuration tools, and provides support for industry-standard IDEs to fast-track your embedded application development. |
Infineon provides a wealth of data at www.infineon.com to help you select the right device, and quickly and effectively integrate it into your design.
Document title: CE237100 – emUSB-Device: Audio device
| Version | Description of change |
|---|---|
| 1.0.0 | New code example |
| 1.1.0 | Updated to support ModusToolbox™ v3.1 and CAPSENSE™ middleware v4.X |
| 2.0.0 | Updated to support ModusToolbox™ v3.2 Updated to support new audio class with explicit feedback in OUT endpoint and DMA Added support for CY8CEVAL-062S2-MUR-4373EM2, CY8CEVAL-062S2-MUR-4373M2, and CY8CEVAL-062S2-CYW43022CUB kits |
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