README.md

# XMC&trade; MCU: Math square root

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

## Requirements

- [ModusToolbox&trade; software](https://www.infineon.com/modustoolbox) v3.0
- [SEGGER J-Link software](https://www.segger.com/downloads/jlink/#J-LinkSoftwareAndDocumentationPack)
- Programming language: C
- Associated parts: All [XMC&trade; MCU](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/) parts

## Supported toolchains (make variable 'TOOLCHAIN')

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

## Supported kits (make variable 'TARGET')

- [XMC1400 boot kit](https://www.infineon.com/cms/en/product/evaluation-boards/kit_xmc14_boot_001/) (`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 don't have one. Instructions in this document use [Tera Term](https://ttssh2.osdn.jp/index.html.en).

This example requires no additional software or tools.

## Using the code example

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

<details open><summary><b>In Eclipse IDE for ModusToolbox&trade; software</b></summary>

1. Click the **New Application** link in the **Quick Panel** (or, use **File** > **New** > **ModusToolbox Application**). This launches the [Project Creator](https://www.infineon.com/ModusToolboxProjectCreator) 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](https://www.infineon.com/ModusToolboxLibraryManager) 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&trade; software user guide](https://www.infineon.com/MTBEclipseIDEUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/ide_{version}/docs/mtb_ide_user_guide.pdf*).

</details>

<details open><summary><b>In command-line interface (CLI)</b></summary>

ModusToolbox&trade; 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&trade; 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&trade; software installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox&trade; 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](https://github.com/Infineon?q=bsp-manifest&type=&language=&sort=) manifest | Required
`--app-id`   | Defined in the `<id>` field of the [CE](https://github.com/Infineon?q=ce-manifest&type=&language=&sort=) 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

<br>

The following example will clone the "[MATH SQRT](https://github.com/Infineon/mtb-example-xmc-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&trade; software user guide](https://www.infineon.com/ModusToolboxUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/docs_{version}/mtb_user_guide.pdf*).

</details>

<details open><summary><b>In third-party IDEs</b></summary>

**Note:** Only VS Code is supported.

1. Follow the instructions from the **In command-line interface (CLI)** section to create the application, and import the libraries using the `make getlibs` command.

2. 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&trade; software user guide](https://www.infineon.com/ModusToolboxUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/docs_{version}/mtb_user_guide.pdf*).

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

</details>

## Operation

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&trade; 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**

   ![](images/serial_terminal_log.jpg)

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.

## 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&trade; software user guide](https://www.infineon.com/MTBEclipseIDEUserGuide).

## Design and implementation

In this code example, the CORDIC block of the XMC&trade; 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.


## 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**

![](images/usic_uart_settings.jpg)


**Figure 2. USIC Tx settings**

![](images/uart_tx_settings.jpg)


**Figure 3. USIC Rx settings**

![](images/uart_rx_settings.jpg)


**Figure 4. USIC interrupt settings**

![](images/uart_interrupts_settings.jpg)


## Related resources

Resources  | Links
-----------|----------------------------------
Code examples  | [Using ModusToolbox&trade; software](https://github.com/Infineon/Code-Examples-for-ModusToolbox-Software) on GitHub
Device documentation | [XMC1000 family datasheets](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/32-bit-xmc1000-industrial-microcontroller-arm-cortex-m0/#document-group-myInfineon-49) <br> [XMC1000 family technical reference manuals](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/32-bit-xmc1000-industrial-microcontroller-arm-cortex-m0/#document-group-myInfineon-44) <br> [XMC4000 family datasheets](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/32-bit-xmc4000-industrial-microcontroller-arm-cortex-m4/#document-group-myInfineon-49) <br> [XMC4000 family technical reference manuals](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/32-bit-xmc4000-industrial-microcontroller-arm-cortex-m4/#document-group-myInfineon-44)
Development kits | [XMC&trade; eval boards](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/#boards)
Libraries on GitHub | [mtb-xmclib-cat3](https://github.com/Infineon/mtb-xmclib-cat3) – XMC&trade; MCU peripheral library (XMCLib) and docs
Tools | [Eclipse IDE for ModusToolbox&trade; software](https://www.infineon.com/modustoolbox) – ModusToolbox&trade; 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&trade; 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&trade; MCU devices, see [32-bit XMC™ industrial microcontroller based on Arm® Cortex®-M](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/).

## Document history

Document title: *CE232727* – *XMC&trade; 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
------

All other trademarks or registered trademarks referenced herein are the property of their respective owners.

© 2022 Infineon Technologies AG

All Rights Reserved.

### Legal disclaimer

The information given in this document shall in no event be regarded as a guarantee of conditions or characteristics. With respect to any examples or hints given herein, any typical values stated herein and/or any information regarding the application of the device, Infineon Technologies hereby disclaims any and all warranties and liabilities of any kind, including without limitation, warranties of non-infringement of intellectual property rights of any third party.

### Information

For further information on technology, delivery terms and conditions and prices, please contact the nearest Infineon Technologies Office (www.infineon.com).

### Warnings

Due to technical requirements, components may contain dangerous substances. For information on the types in question, please contact the nearest Infineon Technologies Office.

Infineon Technologies components may be used in life-support devices or systems only with the express written approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure of that life-support device or system or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered.

-------------------------------------------------------------------------------
	# 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](https://www.infineon.com/modustoolbox) v3.0
	- [SEGGER J-Link software](https://www.segger.com/downloads/jlink/#J-LinkSoftwareAndDocumentationPack)
	- Programming language: C
	- Associated parts: All [XMC™ MCU](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/) 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')

	- [XMC1400 boot kit](https://www.infineon.com/cms/en/product/evaluation-boards/kit_xmc14_boot_001/) (`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 don't have one. Instructions in this document use [Tera Term](https://ttssh2.osdn.jp/index.html.en).

	This example requires no additional software or tools.

	## Using the code example

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

	<details open><summary><b>In Eclipse IDE for ModusToolbox™ software</b></summary>

	1. Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox Application). This launches the [Project Creator](https://www.infineon.com/ModusToolboxProjectCreator) 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](https://www.infineon.com/ModusToolboxLibraryManager) 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](https://www.infineon.com/MTBEclipseIDEUserGuide) (locally available at {ModusToolbox™ software install directory}/ide_{version}/docs/mtb_ide_user_guide.pdf).

	</details>

	<details open><summary><b>In command-line interface (CLI)</b></summary>

	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](https://github.com/Infineon?q=bsp-manifest&type=&language=&sort=) manifest \| Required
	`--app-id` \| Defined in the `<id>` field of the [CE](https://github.com/Infineon?q=ce-manifest&type=&language=&sort=) 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

	<br>

	The following example will clone the "[MATH SQRT](https://github.com/Infineon/mtb-example-xmc-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](https://www.infineon.com/ModusToolboxUserGuide) (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

	</details>

	<details open><summary><b>In third-party IDEs</b></summary>

	Note: Only VS Code is supported.

	1. Follow the instructions from the In command-line interface (CLI) section to create the application, and import the libraries using the `make getlibs` command.

	2. 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](https://www.infineon.com/ModusToolboxUserGuide) (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

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

	</details>

	## Operation

	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

	![](images/serial_terminal_log.jpg)

	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.

	## 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](https://www.infineon.com/MTBEclipseIDEUserGuide).

	## 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, 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

	![](images/usic_uart_settings.jpg)


	Figure 2. USIC Tx settings

	![](images/uart_tx_settings.jpg)


	Figure 3. USIC Rx settings

	![](images/uart_rx_settings.jpg)


	Figure 4. USIC interrupt settings

	![](images/uart_interrupts_settings.jpg)


	## Related resources

	Resources \| Links
	-----------\|----------------------------------
	Code examples \| [Using ModusToolbox™ software](https://github.com/Infineon/Code-Examples-for-ModusToolbox-Software) on GitHub
	Device documentation \| [XMC1000 family datasheets](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/32-bit-xmc1000-industrial-microcontroller-arm-cortex-m0/#document-group-myInfineon-49) <br> [XMC1000 family technical reference manuals](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/32-bit-xmc1000-industrial-microcontroller-arm-cortex-m0/#document-group-myInfineon-44) <br> [XMC4000 family datasheets](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/32-bit-xmc4000-industrial-microcontroller-arm-cortex-m4/#document-group-myInfineon-49) <br> [XMC4000 family technical reference manuals](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/32-bit-xmc4000-industrial-microcontroller-arm-cortex-m4/#document-group-myInfineon-44)
	Development kits \| [XMC™ eval boards](https://www.infineon.com/cms/en/product/microcontroller/32-bit-industrial-microcontroller-based-on-arm-cortex-m/#boards)
	Libraries on GitHub \| [mtb-xmclib-cat3](https://github.com/Infineon/mtb-xmclib-cat3) – XMC™ MCU peripheral library (XMCLib) and docs
	Tools \| [Eclipse IDE for ModusToolbox™ software](https://www.infineon.com/modustoolbox) – 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](https://www.infineon.com/cms/en/product/microcontroller/32-bit-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
	------

	All other trademarks or registered trademarks referenced herein are the property of their respective owners.

	© 2022 Infineon Technologies AG

	All Rights Reserved.

	### Legal disclaimer

	The information given in this document shall in no event be regarded as a guarantee of conditions or characteristics. With respect to any examples or hints given herein, any typical values stated herein and/or any information regarding the application of the device, Infineon Technologies hereby disclaims any and all warranties and liabilities of any kind, including without limitation, warranties of non-infringement of intellectual property rights of any third party.

	### Information

	For further information on technology, delivery terms and conditions and prices, please contact the nearest Infineon Technologies Office (www.infineon.com).

	### Warnings

	Due to technical requirements, components may contain dangerous substances. For information on the types in question, please contact the nearest Infineon Technologies Office.

	Infineon Technologies components may be used in life-support devices or systems only with the express written approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure of that life-support device or system or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered.

	-------------------------------------------------------------------------------