This repository is deprecated. Use the ModusToolbox™ example available here - https://github.com/Infineon/mtb-example-usb-device-audio-freertos
This example demonstrates how to use PSoC® 6 MCU to implement a USB audio device and HID audio playback control that connects to the PC via the USB interface. The example uses FreeRTOS.
This code example shows how to use the PSoC 6 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 PSoC 6 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 headphone. The same audio codec can input microphone data and stream to the PSoC 6 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 PSoC 6 MCU device. Any press on CapSense buttons are reported back to the host over USB HID Consumer Control.
Figure 1. Block Diagram
Provide feedback on this Code Example.
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Note: This code example version requires ModusToolbox software version 2.2 or later and is not backward compatible with v2.1 or older versions. If you can't move to ModusToolbox v2.2, please use the latest compatible version of this example: latest-v1.X.
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Board Support Package (BSP) minimum required version: 2.0.0
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Programming Language: C
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Associated Parts: All PSoC 6 MCU parts with USB
- GNU Arm® Embedded Compiler v9.3.1 (GCC_ARM) - Default value of
TOOLCHAIN - Arm compiler v6.11 (ARM)
- IAR C/C++ compiler v8.42.2 (IAR)
- PSoC 6 Wi-Fi BT Prototyping Kit (CY8CPROTO-062-4343W) - Default target
- PSoC 6 WiFi-BT Pioneer Kit (CY8CKIT-062-WIFI-BT)
- PSoC 62S2 Wi-Fi BT Pioneer Kit (CY8CKIT-062S2-43012)
- PSoC 62S1 Wi-Fi BT Pioneer Kit (CYW9P62S1-43438EVB-01)
- PSoC 62S1 Wi-Fi BT Pioneer Kit (CYW9P62S1-43012EVB-01)
- PSoC 64 Secure Boot Wi-Fi BT Pioneer Kit (CY8CKIT-064B0S2-4343W)
You must connect the CY8CKIT-028-TFT shield to the Arduino header if you are using any of the pioneer kits. You need a third-party module - Pmod I2S2: Stereo Audio Input and Output if you are using the CY8CPROTO-062-4343W kit. You need to solder this module to the Pmod header J15 on the kit.
Note: The PSoC 6 BLE Pioneer Kit (CY8CKIT-062-BLE) and the PSoC 6 WiFi-BT Pioneer Kit (CY8CKIT-062-WIFI-BT) ship with KitProg2 installed. 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.
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Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox Application).
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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 on 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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Optionally, change the suggested New Application Name.
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Enter the local path in the Application(s) Root Path field to indicate where the application needs to be created.
Applications that can share libraries can be placed 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 User Guide (locally available at {ModusToolbox install directory}/ide_{version}/docs/mt_ide_user_guide.pdf).
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Download and unzip this repository onto your local machine, or clone the repository.
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Open a CLI terminal and navigate to the application folder.
On Linux and macOS, you can use any terminal application. On Windows, navigate to the modus-shell directory ({ModusToolbox install directory}/tools_<version>/modus-shell) and run Cygwin.bat.
Note: Ensure that the deps folder contains the required BSP file (TARGET_xxx.mtb) corresponding to the TARGET. Use the Library Manager (
make modlibscommand) to select and download the BSP file. If the selected kit does not have the required resources or is not supported, the application may not work. -
Import the required libraries by executing the
make getlibscommand.
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Follow the instructions from the CLI section to download or clone the repository, and import the libraries using the
make getlibscommand. -
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.
For more details, see the "Exporting to IDEs" section of the ModusToolbox User Guide (locally available at {ModusToolbox install directory}/docs_{version}/mtb_user_guide.pdf.
If using a PSoC 64 Secure MCU kit (like CY8CKIT-064B0S2-4343W), the PSoC 64 Secure MCU must be provisioned with keys and policies before being programmed. Follow the instructions in the Secure Boot SDK User Guide to provision the device. If the kit is already provisioned, copy-paste the keys and policy folder to the application folder.
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Connect the CY8CKIT-028-TFT shield to the Pioneer Kit, or connect Pmod I2S2 to the CY8CPROTO-062-4343W kit.
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Connect the board to your PC using the provided USB cable through the KitProg USB connector.
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Program the board.
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Using Eclipse IDE for ModusToolbox:
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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).
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Using CLI:
From the terminal, execute the
make programcommand to build and program the application using the default toolchain to the default target. You can specify a target and toolchain manually:make program TARGET=<BSP> TOOLCHAIN=<toolchain>Example:
make program TARGET=CY8CPROTO-062-4343W TOOLCHAIN=GCC_ARMNote: Before building the application, ensure that the deps folder contains the BSP file (TARGET_xxx.mtb) corresponding to the TARGET. Execute the
make getlibscommand to fetch the BSP contents before building the application.After programming, the application starts automatically.
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Connect a headphone or earphone to the audio jack of the CY8CKIT-028-TFT shield, or to the Pmod I2S2 audio jack.
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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 computer, verify that a new USB device was enumerated as a Speaker/Microphone and named as "PSoC 6 USB Audio Device".
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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 "PSoC 6 USB Audio Device".
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Record some sound. In Audacity, press Record
. Stop at any time by pressing Stop 
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Play the record by pressing Play
and confirm that the sound was recorded correctly. -
Open a music player in the PC and start playing a song. Use the CapSense slider to change the volume.
Note: You might need to set the Speaker "PSoC 6 USB Audio Device" 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 sound track.
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Press the right CapSense button (BTN1) in the kit to stop a sound track.
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 more 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 of main(). This means that some code executes twice - 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 microphone. The PMod I2S2 module contains the Cirrus CS5343 and Cirrus CS4344 converters.
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 Master (Tx) and Slave (Rx).
If using Pmod I2S2, you do not need to configure it over I2C; the I2S interface operates as Master only (Tx and 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 48 ksps and 44.1 ksps, requiring MCLK of 18.432 MHz and 16.9344 MHz, respectively.
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 USB descriptor implements the Audio Device Class with four endpoints and the HID Device Class with one endpoint:
- Audio Control Endpoint: Controls the access to the audio streams
- 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 stream
The USB buffers store interleaved 24-bit audio stereo data. However, the I2S FIFO requires 32-bit accesses, even if you configured the FIFO word length to be 24-bit. To handle this disparity, the Audio OUT endpoint handler converts the USB 24-bit array to a 32-bit array, and then writes the 32-bit array to the I2S Tx FIFO. The Audio IN endpoint handler reads the 32-bit data from the I2S Rx FIFO, and then converts the 32-bit array to a 24-bit array.
The example project firmware uses FreeRTOS on the CM4 CPU. The following tasks are created in main.c:
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Audio App Task: Implements the high-level functions related to the audio. For example, requests to change the sample rate 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.
The example also uses the FreeRTOS Event Group, which notifies tasks when USB events occur.
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 (48 ksps or 44.1 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 48000 x 2 x 0.001 = 96 samples. Note that the Audio IN Endpoint Callback reads all the data available in the I2S Rx FIFO. In ideal conditions, it would read 96 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.
There is also a mechanism to synchronize the clocks between USB host and the PSoC 6 MCU audio subsystem in the OUT endpoint flow. It uses the Feedback Endpoint callback to report back to the USB host how fast I2S Tx streams the data, so that the host can increase or decrease the sample rate.
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 sound track, and the right button (BTN1) stops a sound track. 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.
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 user tasks and starts the RTOS scheduler. It also implements the Idle task. |
| audio_app.c/h | Contain the task that handle 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 USBFS descriptor. |
| usb_comm.c/h | Contain macros and functions related to the USBFS block and USB Audio Device class. |
| audio_feed.c/h | Implement the Audio Feedback Endpoint callback. |
| 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 setting 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 (PDL) | 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 |
| Application Notes | |
|---|---|
| AN228571 – Getting Started with PSoC 6 MCU on ModusToolbox | Describes PSoC 6 MCU devices and how to build your first application with ModusToolbox |
| AN221774 – Getting Started with PSoC 6 MCU on PSoC Creator | Describes PSoC 6 MCU devices and how to build your first application with PSoC Creator |
| AN210781 – Getting Started with PSoC 6 MCU with Bluetooth Low Energy (BLE) Connectivity on PSoC Creator | Describes PSoC 6 MCU with BLE Connectivity devices and how to build your first application with PSoC Creator |
| AN215656 – PSoC 6 MCU: Dual-CPU System Design | Describes the dual-CPU architecture in PSoC 6 MCU, and shows how to build a simple dual-CPU design |
| Code Examples | |
| Using ModusToolbox | Using PSoC Creator |
| Device Documentation | |
| PSoC 6 MCU Datasheets | PSoC 6 Technical Reference Manuals |
| Development Kits | Buy at www.cypress.com |
| CY8CKIT-062-BLE PSoC 6 BLE Pioneer Kit | CY8CKIT-062-WiFi-BT PSoC 6 WiFi-BT Pioneer Kit |
| CY8CPROTO-063-BLE PSoC 6 BLE Prototyping Kit | CY8CPROTO-062-4343W PSoC 6 Wi-Fi BT Prototyping Kit |
| CY8CKIT-062S2-43012 PSoC 62S2 Wi-Fi BT Pioneer Kit | CY8CPROTO-062S3-4343W PSoC 62S3 Wi-Fi BT Prototyping Kit |
| CYW9P62S1-43438EVB-01 PSoC 62S1 Wi-Fi BT Pioneer Kit | CYW9P62S1-43012EVB-01 PSoC 62S1 Wi-Fi BT Pioneer Kit |
| CY8CKIT-064B0S2-4343W PSoC 64 Secure Boot Wi-Fi BT Pioneer Kit | CY8CKIT-064B0S-4343W PSoC 64 Wi-Fi BT Pioneer Kit |
| Libraries | |
| PSoC 6 Peripheral Driver Library (PDL) and docs | psoc6pdl on GitHub |
| Cypress Hardware Abstraction Layer (HAL) Library and docs | psoc6hal on GitHub |
| RetargetIO - A utility library to retarget the standard input/output (STDIO) messages to a UART port | retarget-io on GitHub |
| Middleware | |
| CapSense library and docs | capsense on GitHub |
| USB Device library and docs | usbdev on GitHub |
| Links to all PSoC 6 MCU Middleware | psoc6-middleware on GitHub |
| Tools | |
| Eclipse IDE for ModusToolbox | The cross-platform, Eclipse-based IDE for IoT designers that supports application configuration and development targeting converged MCU and wireless systems. |
| PSoC Creator | The Cypress IDE for PSoC and FM0+ MCU development. |
Cypress provides a wealth of data at www.cypress.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 Cypress community.
Document Title: CE224997 - PSoC 6 MCU: USB Audio Device with FreeRTOS
| Version | Description of Change |
|---|---|
| 1.0.0 | New code example |
| 1.1.0 | Updated to support ModusToolbox software v2.1, add new kits Cosmetic changes to code |
| 1.1.1 | Minor documentation updates |
| 1.2.0 | Fixed volume control issue |
| 2.0.0 | Major update to support ModusToolbox software v2.2, added support for new kits This version is not backward compatible with ModusToolbox software v2.1 |
| 2.0.1 | Minor documentation updates, added feedback link |
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