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/stop
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/stop 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™ software v3.1 or later (tested with v3.1)
- 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 v9.30.1 (
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)
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. The ModusToolbox™ software 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".
This example uses the Audacity tool to record and play sound. You can also use any software tool that plays music.
Create the project and open it using one of the following:
In Eclipse IDE for ModusToolbox™ software
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Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox™ Application). This launches the Project Creator tool.
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Pick a kit supported by the code example from the list shown in the Project Creator - Choose Board Support Package (BSP) dialog. When you select a supported kit, the example is reconfigured automatically to work with the kit. To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can use the Library Manager to select or update the BSP and firmware libraries used in this application. To access the Library Manager, click the link from the Quick Panel.
You can also just start the application creation process again and select a different kit.
If you want to use the application 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.
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In the Project Creator - Select Application dialog, choose the example by enabling the checkbox.
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(Optional) Change the suggested New Application Name.
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The Application(s) Root Path defaults to the Eclipse workspace which is usually the desired location for the application. If you want to store the application in a different location, you can change the Application(s) Root Path value. Applications that share libraries should be in the same root path.
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Click Create to complete the application creation process.
For more details, see the Eclipse IDE for ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mt_ide_user_guide.pdf).
In command-line interface (CLI)
ModusToolbox™ software provides the Project Creator as both a GUI tool and the command line tool, "project-creator-cli". The 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™ software 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™ software installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox™ software 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 "project-creator-cli" tool has the following arguments:
| Argument | Description | Required/optional |
|---|---|---|
--board-id |
Defined in the <id> field of the BSP manifest |
Required |
--app-id |
Defined in the <id> 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 |
The following example clones the "[mtb-example-usb-device-audio-freertos](https://github.com/Infineon/mtb-example-usb-device-audio-freertos)" application with the desired name "USBAaudioRecorder" 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 USBAudioRecorder --target-dir "C:/mtb_projects"
Note: The project-creator-cli tool uses the git clone and make getlibs commands to fetch the repository and import the required libraries. For details, see the "Project creator tools" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).
To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can invoke the Library Manager GUI tool from the terminal using make library-manager command or use the Library Manager CLI tool "library-manager-cli" to change the BSP.
The "library-manager-cli" tool has the following arguments:
| Argument | Description | Required/optional |
|---|---|---|
--add-bsp-name |
Name of the BSP that should be added to the application | Required |
--set-active-bsp |
Name of the BSP that should be as active BSP for the application | Required |
--add-bsp-version |
Specify the version of the BSP that should be added to the application if you do not wish to use the latest from manifest | Optional |
--add-bsp-location |
Specify the location of the BSP (local/shared) if you prefer to add the BSP in a shared path | Optional |
Following example adds the CY8CKIT-062-WIFI-BT BSP to the already created application and makes it the active BSP for the app:
~/ModusToolbox/tools_3.1/library-manager/library-manager-cli --project "C:/mtb_projects/USBAudioRecorder" --add-bsp-name CY8CKIT-062-WIFI-BT --add-bsp-version "latest-v4.X" --add-bsp-location "local"
~/ModusToolbox/tools_3.1/library-manager/library-manager-cli --project "C:/mtb_projects/USBAudioRecorder" --set-active-bsp APP_CY8CKIT-062-WIFI-BT
In third-party IDEs
Use one of the following options:
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Use the standalone Project Creator tool:
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Launch Project Creator from the Windows Start menu or from {ModusToolbox™ software install directory}/tools_{version}/project-creator/project-creator.exe.
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In the initial Choose Board Support Package screen, select the BSP, and click Next.
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In the Select Application screen, select the appropriate IDE from the Target IDE drop-down menu.
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Click Create and follow the instructions printed in the bottom pane to import or open the exported project in the respective IDE.
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Use command-line interface (CLI):
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Follow the instructions from the In command-line interface (CLI) section to create the application.
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Export the application to a supported IDE using the
make <ide>command. -
Follow the instructions displayed in the terminal to create or import the application as an IDE project.
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For a list of supported IDEs and more details, see the "Exporting to IDEs" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).
Note: Initially, the customized configuration files such as design.cyqspi, design.cycapsense, and design.modus are present in the templates/TARGET_< BSP-NAME >/config folder and are copied automatically from this folder to bsps/TARGET_< BSP-NAME >/config during library updates. The build system reads all these configurations from the bsps/TARGET_< BSP-NAME >/config folder.
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Connect the CY8CKIT-028-TFT shield to the Pioneer Kit.
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Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.
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Program the board using one of the following:
Using Eclipse IDE for ModusToolbox™ software
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Select the application project in the Project Explorer.
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In the Quick Panel, scroll down, and click <Application Name> Program (KitProg3_MiniProg4).
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_ARM**Note:** Before building the application, ensure that the *deps* folder contains the BSP file (*TARGET_xxx.mtb*) corresponding to the TARGET. Execute the `make getlibs` command to fetch the BSP contents before building the application. After programming, the application starts automatically. -
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Connect a headphone or earphones to the audio jack of the CY8CKIT-028-TFT shield.
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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).
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On the PC, verify that a new USB device is enumerated as a Speaker/Microphone and named as "4-Audio Control".
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Use your audio software to specify the microphone or speaker. In the Audacity software tool, select the microphone and speaker name as "4-Audio Control".
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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 "4-Audio Control" as the default speaker device in your OS.
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Press the left CAPSENSE™ button (BTN0) in the kit to play/pause a soundtrack.
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Press the right CAPSENSE™ button (BTN1) in the kit to stop a soundtrack.
You can debug the example to step through the code. In the 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™ software user guide.
Note: (Only while debugging) On the CM4 CPU, some code in main() may execute before the debugger halts at the beginning of main(). 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 of main(). See KBA231071 to learn about this and for the workaround.
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 two 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
- 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:
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Audio app task: Implements the high-level functions related to the audio. For example, requests to and volume.
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Audio IN task: Implements the functions related to the audio IN Endpoint.
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Audio OUT task: Implements the functions related to the audio OUT Endpoint.
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Touch task: Implements the user interface related to CAPSENSE™.
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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 and the right button (BTN1) stops 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.
This code example has the following limitations:
-
The emUSB-device descriptor has provision only to initialize IN and OUT endpoints. A third FEEDBACK endpoint cannot be initialized. The purpose of the FEEDBACK endpoint is to synchronize the clocks between the USB host and the PSoC™ 6 MCU audio subsystem in the OUT endpoint flow.
-
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 task that handles the audio-related blocks, such as the USB audio events and I2S control. |
| audio_in.c/h | Contain the task that handles recording requests to the Audio IN endpoint. These files also implement the Audio IN Data Endpoint callback. |
| audio_out.c/h | Contain the task that handles playing requests to the Audio OUT endpoint. These files also implement the Audio OUT Data endpoint callback. |
| audio.h | Contains macros related to the emUSB-device descriptor. |
| cycfg_emusbdev.c/h | Contain macros and functions related to the USBFS block and USB audio device class. |
| 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™ software AN215656 – PSoC™ 6 MCU: Dual-CPU system design |
| Code examples | Using ModusToolbox™ software 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 | Eclipse IDE for ModusToolbox™ software – ModusToolbox™ software is a collection of easy-to-use software and tools enabling rapid development with Infineon MCUs, covering applications from embedded sense and control to wireless and cloud-connected systems using AIROC™ Wi-Fi and Bluetooth® connectivity devices. |
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.
For PSoC™ 6 MCU devices, see How to design with PSoC™ 6 MCU - KBA223067 in the Infineon Developer community.
Document title: CE237100 – emUSB-Device: Audio device
| Version | Description of change |
|---|---|
| 1.0.0 | New code example |
| 1.1.0 | Update to support ModusToolbox™ v3.1 and CAPSENSE™ middleware v4.X |
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