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.

• ModusToolbox™ software v3.0
• SEGGER J-Link software
• Programming language: C
• Associated parts: All XMC™ MCU parts

• 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)

• XMC1400 boot kit (KIT_XMC14_BOOT_001) - Default value of TARGET

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

Install a terminal emulator if you don't have one. Instructions in this document use Tera Term.

This example requires no additional software or tools.

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

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"

1. Connect the board to your PC using a micro-USB cable through the debug USB connector.

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

3. 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).

4. 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

   

5. Change the value of the INPUT_NUM macro to try another number as the input.

6. 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.

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.

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, 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.

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

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 title: CE232727 – XMC™ MCU: Math square root

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