PSoC™ 6 MCU: Smart I/O I2S master

This code example uses a SPI resource and smart I/O in PSoC™ 6 MCU to implement the Inter-IC Sound (I2S) master interface (Tx only).

View this README on GitHub.

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Requirements

ModusToolbox™ v3.0 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

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™ 6 Bluetooth® LE Prototyping Kit (CY8CPROTO-063-BLE)
PSoC™ 62S2 Wi-Fi Bluetooth® Pioneer Kit (CY8CKIT-062S2-43012)
PSoC™ 64 "Secure Boot" Wi-Fi Bluetooth® Pioneer Kit (CY8CKIT-064B0S2-4343W)
PSoC™ 62S4 Pioneer Kit (CY8CKIT-062S4)
PSoC™ 62S2 Evaluation Kit (CY8CEVAL-062S2, CY8CEVAL-062S2-LAI-4373M2, CY8CEVAL-062S2-MUR-43439M2, CY8CEVAL-062S2-LAI-43439M2)

Hardware setup

You need a third-party module - Pmod I2S2: stereo audio input and output to run this application. Additionally, you must manually wire the following connections:

I2S signal	Kit pins	Pmod IS2S pins
TX_SCK	P9[2]	J1.3
TX_DATA	P9[0]	J1.4
TX_WS	P9[3]	J1.2
MCLK	See Table 1	J1.1
GND	GND	GND
VCC	V3.3	VCC

See Table 1 to determine the MCLK pin for the respective kits:

Table 1. MCLK_PIN selection for different targets

Kit	MCLK_PIN
CY8CPROTO-062-4343W	P5 [6]
CY8CKIT-062-WIFI-BT	P5 [6]
CY8CKIT-062-BLE	P5 [6]
CY8CPROTO-063-BLE	P5 [6]
CY8CKIT-062S2-43012	P5 [6]
CY8CKIT-064B0S2-4343W	P5 [6]
CY8CKIT-062S4	P5 [6]
CY8CEVAL-062S2	P5 [6]
CY8CEVAL-062S2-LAI-4373M2	P5 [6]
CY8CEVAL-062S2-MUR-43439M2	P5 [6]
CY8CEVAL-062S2-LAI-43439M2	P5 [6]

Note: Only Port 9 and Port 8 support smart I/O; this means that the I2S master can be placed only on pins 0–3 of these two ports. Note the following when using these connections:

On PSoC™ 6 Bluetooth® LE Pioneer Kit (CY8CKIT-062-BLE), add a zero-ohm resistor at R131.
On PSoC™ 6 Wi-Fi Bluetooth® Pioneer Kit (CY8CKIT-062-WIFI-BT), add a zero-ohm resistor at R162.
On PSoC™ 62S4 Pioneer Kit (CY8CKIT-062S4), remove resistor R68 and add a zero-ohm resistor at R135.
On PSoC™ 62S2 Evaluation Kit (CY8CEVAL-062S2), disconnect the zero-ohm resistor from R100 and connect to R104.

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".

Software setup

See the ModusToolbox™ tools package installation guide for information about installing and configuring the tools package. This example requires no additional software or tools.

Using the code example

Create the project

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 "PSoC™ 6 MCU: Smart I/O I2S master" application with the desired name "PSoC6SmartIO" 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-smartio-i2s --user-app-name PSoC6SmartIO --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 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™ tools package user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).

Open the project

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).

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.

Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.
Ensure that the MCLK_PIN macro is assigned to the value mentioned in Table 1 for the respective kits.
Connect a speaker or headphone to the Pmod I2S2 audio jack (green connector).
Program the board using one of the following:
Using Eclipse IDE
1. Select the application project in the Project Explorer.
2. 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 program command 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
```
After programming, the application starts automatically. Press the user button to play the short audio "PSoC™ Rocks".

Debugging

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 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.

In other IDEs

Follow the instructions in your preferred IDE.

Design and implementation

This design provides middleware files (i2s_master.c/h) to implement the I2S master (Tx only). It requires an SPI resource and smart I/O. All the initialization of these blocks are handled by the middleware. You need to configure only the clocks and pin assignment for the SPI and smart I/O.

Note: The initialisation of SmartIO and SPI configurations is handled in the i2c_master.c/h files. The changes done to SmartIO and SCB configuration in device configurator get overridden.

I2S interface overview

The I2S interface timing diagram is shown below. It streams audio data for two channels: left and right. The Word Select (WS) signal indicates the channel that is currently streaming.

Figure 1. I2S timing diagram (from I2S Bus spec)

Due to the similarities to the SPI interface, you can leverage the SPI master to generate the clock (SCK) and the data signal (SD). The WS signal can be derived from the SPI-SS signal; however, it needs to keep toggling on every channel. In this implementation, the I2S channel length is 32 bits. Smart I/O is configured to toggle the WS signal every 32 cycles of SCK. It initially toggles when the SPI-SS signal asserts (beginning of transmission). Because the PSoC™ 6 SPI can support data width up to 16 bits only, the SPI FIFO needs to be written twice for every I2S channel.

Table 2. SPI and SGPIO mapping

SPI signal	I2S signal	Description
SCLK	TX_SCK (SCK)	Clock driven by the I2S master
MOSI	TX_DATA (SD)	Data driven by the I2S master
SS	TX_WS (WS)	Indicates which channel transmits

Clocking

The clock that drives the I2S/SPI depends on the required frame rate. Typical frame rate values are 8/16/22.05/32/44.1/48 kHz. The formula to calculate the clock frequency based on the required frame rate is:

$$Clock frequency [Hz] = Frame rate [Hz] * 2 * Channel length * SPI oversample$$

In this implementation, the channel length is fixed to 32 and the SPI oversample is fixed to 4.

Usually an audio codec requires a master clock (MCLK). In this case, a PWM is used to generate MCLK. This clock is usually 256x faster than the frame rate (see the audio codec's datasheet).

Table 3 shows a summary of the frequencies to be configured in the system for a given frame rate.

Table 3. SPI and SGPIO mapping

Frame rate	I2S SCK	SPI clock	MCLK	Peripheral clock
8 kHz	0.512 MHz	2.048 MHz	2.048 MHz	4.096 MHz
16 kHz	1.024 MHz	4.096 MHz	4.096 MHz	16.384 MHz
22.05 kHz	1.4112 MHz	5.6448 MHz	5.6448 MHz	22.5792 MHz
32 kHz	2.048 MHz	8.192 MHz	8.192 MHz	32.768 MHz
44.1 kHz	2.822 MHz	11.2896 MHz	11.2896 MHz	45.1584 MHz
48 kHz	3.072 MHz	12.288 MHz	12.288 MHz	49.152 MHz

In this example, the PLL is configured to source the CPU clocks (HFCLK0) and be 3x the peripheral clock. This example uses the 16 kHz frame rate. So, the PLL0 is set to 49.152 MHz to achieve a 16 kHz sample rate (16.384 MHz * 3 = 49.152 MHz). To obtain other frame rates, modify the PLL0 clock value such that the SCB clock frequency in the device configuration matches the SPI clock as mentioned in the above table.

Figure 2. SCB clock parameters

Firmware overview

The firmware is designed to play a short audio record placed in flash (wave.h/c file) when the kit's button is pressed.

The I2S master init function requires an SPI resource and a smart I/O resource as arguments. The SPI resource is configured to generate an interrupt when the FIFO is half full. When the I2S master write function is invoked, it writes data to the SPI FIFO until it is full. Once the FIFO level drops to half, it triggers the interrupt and more data is written to the FIFO. The firmware also registers a callback to be executed when the I2S Write operation finishes.

The smart I/O resource is configured to translate the SPI-SS to I2S-WS signal. It uses the internal LUTs and data unit (DU) to count 32 cycles of the SPI-SCLK, and then toggle the I2S-WS output. It also delays the SPI-MOSI line to match the I2S bit arrangement.

Resources and settings

Table 4. Application resources

Resource	Alias/object	Purpose
SCB (SPI) (PDL)	SPI_I2S	Simulates the I2S master
Smart I/O (PDL)	SMARTIO	Used by the I2S master middleware to translate SPI to I2S
GPIO (HAL)	CYBSP_USER_BTN	User button
GPIO (HAL)	CYBSP_USER_LED	User LED
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™ 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	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.

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.

Document history

Document title: CE231443 – PSoC™ 6 MCU: Smart I/O I2S master

Version	Description of change
1.0.0	New code example
1.1.0	Updated to support ModusToolbox™ v2.3. Added support for CY8CKIT-062S4
1.2.0	Added support for CY8CEVAL-062S2, CY8CEVAL-062S2-LAI-4373M2
1.3.0	Removed target specific macros from the source code
2.0.0	Major update to support ModusToolbox™ v3.0. This version is not backward compatible with previous versions of ModusToolbox™
2.1.0	Added support for `CY8CEVAL-062S2-MUR-43439M2`, `CY8CEVAL-062S2-LAI-43439M2`, and corrected pin assignments for MCLK on all BSPs
2.2.0	Enabled chipSyncEn bits for SCL and SS pins. Updated clock configuration for `CY8CEVAL-062S2-MUR-43439M2`, `CY8CEVAL-062S2-LAI-43439M2`, and `CY8CEVAL-062S2-LAI-4373M2` BSPs.

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