PSoC™ 6 MCU: PDM to I2S example

This code example demonstrates how to route pulse-density modulation (PDM) audio data to the inter-IC sound (I2S) interface in PSoC™ 6 MCU.

Overview

This code example shows how to record a short audio sample from a microphone, and then play it on a speaker or headphone. The example uses the PDM/PCM block to interface with a digital microphone. All recorded data is stored in the internal SRAM. Once the recording completes, the I2S block starts sending data to an external audio codec. Press the user button on the kit to record an audio sample. Once the button is released, it plays back the recorded audio when the button was pressed.

Figure 1. Block diagram

Requirements

• ModusToolbox™ software v3.0 or later (tested with v3.0)

• PSoC™ 6 Board support package (BSP) minimum required version: 4.0.0

• Programming language: C

• Associated parts: All PSoC™ 6 MCU parts with audio subsystem

Supported toolchains (make variable 'TOOLCHAIN')

• GNU Arm® embedded compiler v10.3.1 (GCC_ARM) - Default value of TOOLCHAIN
• Arm® compiler v6.16 (ARM)
• IAR C/C++ compiler v9.30.1 (IAR)

Supported kits (make variable 'TARGET')

• PSoC™ 6 Wi-Fi Bluetooth® prototyping kit (CY8CPROTO-062-4343W)
• PSoC™ 6 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062-WIFI-BT) - Default value of TARGET
• PSoC™ 6 Bluetooth® LE pioneer kit (CY8CKIT-062-BLE)
• 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™ 64 "Secure Boot" Wi-Fi Bluetooth® pioneer kit (CY8CKIT-064B0S2-4343W)

Hardware setup

This code example requires the TFT display shield board CY8CKIT-028-TFT, which has the audio codec. This board comes with CY8CKIT-062-WIFI-BT. It can also be purchased standalone and be used with any other Arduino-compatible PSoC™ 6 MCU kit.

Alternatively, you can use a third-party module - Pmod I2S2: Stereo audio input and output if you are using a prototyping kit, such as CY8CPROTO-062-4343W.

If using the Pmod I2S2 module, make the following connections:

I2S signal	Kit pin	Pmod IS2S pin
TX_SCK	P5[1]	J1.2
TX_DATA	P5[3]	J1.4
TX_WS	P5[2]	J1.3
MCLK	P5[0]	J1.1
GND	GND	GND
VCC	VTARG	VCC

Note: If using CY8CPROTO-062-4343W, you can solder the Pmod I2S2 module to the kit's Pmod header J15.

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".

Software setup

This example requires no additional software or tools.

Using the code example

Create the project and open it using one of the following:

In Eclipse IDE for ModusToolbox™ software

1. Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox™ Application). This launches the Project Creator tool.

2. 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.

3. In the Project Creator - Select Application dialog, choose the example by enabling the checkbox.

4. (Optional) Change the suggested New Application Name.

5. 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.

6. 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-psoc6-pdm-to-i2s" application with the desired name "PdmI2s" configured for the CY8CPROTO-062-4343W* BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CPROTO-062-4343W --app-id mtb-example-psoc6-pdm-to-i2s --user-app-name PdmI2s --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:

library-manager-cli --project "C:/mtb_projects/PdmI2s" --add-bsp-name CY8CKIT-062-WIFI-BT --add-bsp-version "latest-v4.X" --add-bsp-location "local"

library-manager-cli --project "C:/mtb_projects/PdmI2s" --set-active-bsp APP_CY8CKIT-062-WIFI-BT

In third-party IDEs

Use one of the following options:

• Use the standalone Project Creator tool:

  1. Launch Project Creator from the Windows Start menu or from {ModusToolbox™ software install directory}/tools_{version}/project-creator/project-creator.exe.

  2. In the initial Choose Board Support Package screen, select the BSP, and click Next.

  3. In the Select Application screen, select the appropriate IDE from the Target IDE drop-down menu.

  4. Click Create and follow the instructions printed in the bottom pane to import or open the exported project in the respective IDE.

• Use command-line interface (CLI):

  1. Follow the instructions from the In command-line interface (CLI) section to create the application.

  2. Export the application to a supported IDE using the make <ide> command.

  3. Follow the instructions displayed in the terminal to create or import the application as an IDE project.

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).

Operation

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.

1. Connect the TFT display shield to the main board. If using the Pmod I2S2 module, connect to the prototyping kit.

2. Connect the board to your PC using the provided USB cable through the USB connector.

3. Connect a speaker or headphone to the audio jack located in the TFT display shield board (CY8CKIT-028-TFT), or to the Pmod I2S2 green audio jack.

4. If you are not using one of the Arduino kits (TFT-028 with AK4954A), please comment DEFINES+=USE_AK4954A

5. Program the board.

   • Using Eclipse IDE for ModusToolbox:

     1. Select the application project in the Project Explorer.

     2. In the Quick Panel, scroll down, and click <Application Name> Program (KitProg3_MiniProg4).

   • Using CLI:

     From the terminal, execute the make program command 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_ARM
     

6. After programming, the application starts automatically. Press the user button and hold it. Speak over the microphone to record a short message (up to 2 seconds).

7. Release the user button and listen to the recorded message with the headphone or speaker.

Debugging

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 - 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.

Design and implementation

The CY8CKIT-028-TFT shield contains the audio codec AK4954A, an audio jack, and a digital microphone. This allows you to record data using the microphone and play it with the audio codec. You can connect a speaker or headphone to the audio jack.

The first stage is to record any sound coming from the microphone and place it in the SRAM of PSoC™ 6 MCU. This whole process can be achieved using PDM/PCM driver to transfer the data from the Rx buffer to an array allocated in the SRAM. Once the sound is recorded, the I2S driver transfers data from the SRAM to the Tx buffer.

To record a longer audio stream from the microphone, a sample rate of only 8 ksps is configured in both hardware blocks - PDM/PCM and I2S. The word length of the PDM/PCM Rx buffer and the I2S Tx buffer are set to 16 bits. The number of elements allocated for the recorded data array is 65,536, consuming a total of 128 KB of SRAM.

PSoC™ 6 MCU also provides the clock source for the audio codec. Based on the AK4954A datasheet, this codec requires an 2.048 MHz MCLK to sample at 8 kHz. The code example contains an I2C master, through which PSoC™ 6 MCU configures the audio codec. The code example includes the AK4954A library (deps/audio-codec-ak4954a.mtb) dependency to easily configure the AK4954A. If you do not desire to use the AK4954A, you can edit the Makefile to remove the line DEFINES+=USE_AK4954A.

MCLK is generated by using a PWM running at the desired frequency. The clock that is used to source the PWM and the audio subsystem must be the same to avoid any synchronization issues. This example uses the PLL to source the CPU/peripherals and the audio subsystem.

Note: The desired frequency values set in this code example cannot be achieved by sourcing the PLL from the IMO (8 MHz). Therefore, slightly different values are enforced in the firmware to avoid issues during the initialization of the PWM and I2S.

Figure 2. Flowchart

For more details on I2S and PDM/PCM interfaces, see the architecture TRM of the device.

Resources and settings

Table 1. Application resources

Resource	Alias/object	Purpose
I2S (HAL)	i2s	Interfaces the audio codec
PDM/PCM (HAL)	pdm_pcm	Interfaces the digital microphone
I2C (HAL)	mi2c	Configures the audio codec
GPIO (HAL)	CYBSP_USER_BTN	Starts a recording and playback
PWM (HAL)	mclk_pwm	Generates the MCLK for the audio codec

Related resources

Resources	Links
Application notes	AN228571 – Getting started with PSoC™ 6 MCU on ModusToolbox™ software AN221774 – Getting started with PSoC™ 6 MCU on PSoC™ Creator AN210781 – Getting started with PSoC™ 6 MCU with Bluetooth® Low Energy (BLE) Connectivity on PSoC™ Creator AN215656 – PSoC™ 6 MCU: Dual-CPU system design
Code examples	Using ModusToolbox™ software on GitHub Using PSoC™ Creator
Device documentation	PSoC™ 6 MCU datasheets PSoC™ 6 technical reference manuals
Development kits	CY8CKIT-062-BLE PSoC™ 6 Bluetooth® LE pioneer kit CY8CKIT-062-WiFi-BT PSoC™ 6 Wi-Fi Bluetooth® pioneer kits
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 audio-codec-ak4954a on GitHub
Middleware on GitHub	capsense – CAPSENSE™ library and documents 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. PSoC™ Creator – IDE for PSoC™ and FM0+ MCU development

Other resources

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 community.

Document history

Document title: CE220762 - PSoC™ 6 MCU: PDM-to-I2S example

Version	Description of change
1.0.0	New code example
1.1.0	Updated folder structure and ak4954a driver
1.2.0	Updated to support ModusToolbox™ software v2.1 Updated to use HAL drivers for PDM/PCM, I2S, and clock resources
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 Added support to new kits
3.0.0	Major update to support ModusToolbox™ v3.0. This version is not backward compatible with previous versions of ModusToolbox™

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