PSoC™ 6 MCU: PDM-to-PCM example

This example demonstrates how to use the pulse-density modulation (PDM)/pulse-code modulation (PCM) hardware block in PSoC™ 6 MCU with a digital microphone.

Overview

This code example shows how to use a digital microphone with the PDM/PCM block. It measures the sound intensity (volume), and turns ON an LED when the volume exceeds a threshold. You can reset the threshold by pressing a switch; you can use this to capture the environment noise and set a new threshold above the noise. A debug UART reports the current volume.

Figure 1. Block diagram

View this README on GitHub.

Provide feedback on this code example.

Requirements

• ModusToolbox™ software v3.0 or later (tested with v3.0)
• Board support package (BSP) minimum required version: v4.0.0
• Programming language: C
• Associated parts: All PSoC™ 6 MCU parts

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) - Default value of TARGET

• PSoC™ 6 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062-WIFI-BT)

• 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 example uses the board's default configuration. See the kit user guide to ensure that the board is configured correctly.

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 If you do not upgrade, you will see an error like "unable to find CMSIS-DAP device" or "KitProg firmware is out of date".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

Install a terminal emulator if you don't have one. See Tera Term for instructions.

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-pcm" application with the desired name "PDMtoPCM" 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-psoc6-pdm-pcm --user-app-name PDMtoPCM --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 CY8CPROTO-062-4343W BSP to the already created application and makes it the active BSP for the app:

library-manager-cli --project "C:/mtb_projects/PDMtoPCM" --add-bsp-name CY8CPROTO-062-4343W --add-bsp-version "latest-v4.X" --add-bsp-location "local"

library-manager-cli --project "C:/mtb_projects/PDMtoPCM" --set-active-bsp APP_CY8CPROTO-062-4343W

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 device 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 board to your PC using the provided USB cable through the KitProg3 USB connector.

2. Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.

3. Program the board using one of the following:

   Using Eclipse IDE for ModusToolbox™ software

   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. The default toolchain and target are specified in the application's Makefile, but you can override those values manually:

   make program TARGET=<BSP> TOOLCHAIN=<toolchain>
   

   Example:

   make program TARGET=CY8CPROTO-062-4343W TOOLCHAIN=GCC_ARM
   

4. After programming, the application starts automatically. Confirm that the serial terminal reports the volume in real time.

5. Touch, speak, or play any sound over the microphone. Observe that the kit's LED turns ON.

6. If the LED is always ON or blinking, without playing any sound over the microphone, press the kit's button to reset the noise threshold.

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 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.

Design and implementation

All the kits supported by this code example come with a digital microphone with a single-bit PDM output. This allows you to convert any audio captured by the microphone into a digital signal (PDM). The PSoC™ 6 MCU device converts this digital signal to a quantized 16-bit value (PCM). An interrupt is triggered when there is enough data to be processed (at least 128 samples). The absolute values of the samples are summed. This represents the overall loudness of the sound, which is proportional to the volume.

The PDM/PCM block is configured for a sampling rate of eight ksps. Because this application only calculates the volume, a higher sample rate for better audio quality is not required. Ideally, the audio wave captured should oscillate around zero. The PDM/PCM hardware integrates a high-pass filter. This filter attenuates low frequencies that add offset to the conversion.

The calculated volume is sent over the UART. Use a terminal program on your PC to observe the data. The code example also turns ON a kit LED when the calculated volume is greater than a predefined threshold. The threshold can be used as a noise threshold so that this example can run in noisy environments. By pressing the kit's button, you can set a new noise threshold based on the current volume. Note that you should remove any source of sound and avoid speaking close to the microphone while pressing the button.

Resources and settings

Table 1. Application resources

Resource	Alias/object	Purpose
PCM/PDM (HAL)	pdm_pcm	To interface with digital microphones
UART (HAL)	cy_retarget_io_uart_obj	UART HAL object used by retarget-io for printing to the console
GPIO (HAL)	CYBSP_USER_LED	User LED to turn when some sound is detected
GPIO (HAL)	CYBSP_USER_BTN	User Button to reset noise threshold
Clock (HAL)	audio_clock	To configure the audio subsystem clock
Clock (HAL)	pll_clock	To configure the PLL clock

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
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	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.

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: CE219431 - PSoC™ 6 MCU: PDM-to-PCM Example

Version	Description of change
1.0.0	New code example
1.1.0	Updated to support ModusToolbox™ software v2.1. Updated to use HAL drivers for PDM/PCM 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. Fixed clock initialization.
3.0.0	Major update to support ModusToolbox™ v3.0 and BSPs v4.X. This version is not backward compatible with previous versions of ModusToolbox™.

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