XMC™ MCU: Math square root

This code example demonstrates the calculation of the square root of an input using the MATH - CORDIC block in XMC™ MCU. The correctness of the result is checked using a software-implemented square root function.

Requirements

ModusToolbox™ software v3.0 or later (tested with v3.4)
SEGGER J-Link software
Programming language: C
Associated parts: All XMC™ MCU parts

Supported toolchains (make variable 'TOOLCHAIN')

GNU Arm® Embedded Compiler v11.3.1 (GCC_ARM) - Default value of TOOLCHAIN

Supported kits (make variable 'TARGET')

XMC1400 boot kit (KIT_XMC14_BOOT_001) - Default value of TARGET

Hardware setup

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

Software setup

Install a terminal emulator if you do not have one. Instructions in this document use Tera Term.

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

Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox Application). This launches the Project Creator tool
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
In the Project Creator - Select Application dialog, choose the example by enabling the checkbox
(Optional) Change the suggested New Application Name
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
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}/ide_{version}/docs/mtb_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.

This 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 will clone the "MATH SQRT" application with the desired name "MATHSqrt" configured for the KIT_XMC14_BOOT_001 BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id KIT_XMC14_BOOT_001 --app-id mtb-example-xmc-math-sqrt --user-app-name MATHSqrt --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).

In third-party IDEs

Note: Only VS Code is supported.

Follow the instructions from the In command-line interface (CLI) section to create the application, and import the libraries using the make getlibs command
Export the application to a supported IDE using the make <ide> command

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

Operation

Connect the board to your PC using a micro-USB cable through the debug USB connector
Open a terminal program and select the JLink CDC COM port. Set the serial port parameters to 8N1 and 115200 baud
Program the board 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 (JLink)
After the device is programmed, the square root CORDIC operation is performed, and the result is displayed on the serial terminal

Figure 1. Serial terminal log
Change the value of the INPUT_NUM macro to try another number as the input
Enable the macro Enable_Q15 macro to compute using Q15 format
Rebuild the code example, and then program the device. The CORDIC operation is repeated on the new number and the result is shown on the serial terminal

Debugging

You can debug the example to step through the code. In the IDE, use the <Application Name> Debug (JLink) configuration in the Quick Panel. For more details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ software user guide.

Design and implementation

In this code example, the CORDIC block of the XMC™ MCU is used to perform the square root operation on an input number. The results are calculated using the square root CORDIC processor API and checked with the result obtained from the software-implemented API (from math.h). The final outputs are displayed on the terminal.

Because the CORDIC processor doesn't support a floating-point unit, the operations take place on 'Q' format numbers in this processor. The X and Y data input for the CORDIC processor can be sent directly in 'Qm.n' format. 'Q' is a binary fixed-point number format, where the number of fractional bits (indicated by 'n') and the number of integer bits (indicated by 'm') are specified. Therefore, the input number should be converted to 'Q' format. In this code example, 0.25F is the input number.

Stage 1: Converts 0.25F to 'Q31' format or 'Q15' format, which is then sent as an argument to the CORDIC processor implementation function. The result is then converted back to a float number and displayed on the UART terminal
Stage 2: Uses the result obtained using the sqrtf() function (function implemented in math.h) to illustrate the accuracy of the result obtained from the CORDIC processor API

The CORDIC algorithm is a useful convergence method, which performs mathematical operations through an iterative process. The main advantage of using this algorithm is the fast calculation speed compared to software, and high accuracy.

Resources and settings

The project uses a custom design.modus file because the following settings were modified in the default design.modus file.

Figure 1. USIC (UART) settings

Figure 2. USIC Tx settings

Figure 3. USIC Rx settings

Figure 4. USIC interrupt settings

Related resources

Resources	Links
Code examples	Using ModusToolbox™ software on GitHub
Device documentation	XMC1000 family datasheets XMC1000 family technical reference manuals XMC4000 family datasheets XMC4000 family technical reference manuals
Development kits	XMC™ eval boards
Libraries on GitHub	mtb-xmclib-cat3 – XMC™ MCU peripheral library (XMCLib) and docs
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 XMC™ MCU devices, see 32-bit XMC™ industrial microcontroller based on Arm® Cortex®-M.

Document history

Document title: CE232727 – XMC™ MCU: Math square root

Version	Description of change
1.0.0	New code example
1.1.0	Added support for new kits
2.0.0	Updated to support ModusToolbox™ software v3.0; CE will not be backward compatible with previous versions of ModusToolbox™ software
2.1.0	Resolved build warnings Added support to compute using 'Q15' format

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License

Infineon/mtb-example-xmc-math-sqrt

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