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# 1.9 DMAC CRC-32 Generation

This example application demonstrates how to use the DMAC peripheral to compute 32-bit Cyclic Redundancy Checksum (CRC).

## Description

The DMAC unit provides support for calculating a CRC-16 and CRC-32 value for data passing through any DMA channel or using an IO interface.

This example application computes the 32-bit CRC value for the polynomial (0x04C11DB7) using below two data sources for the CRC engine in DMAC peripheral

1. It uses a DMA Channel with software trigger to initiate a memory-memory transfer from the source buffer to the destination buffer with 8-bit beat size. Once the transfer is completed a 32-bit CRC will be generated for the source buffer.
2. It uses the IO mode to generate a 32-bit CRC value for the source buffer.

Once the hardware CRC are generated using above two methods they are validated using a software-calculated CRC value.

## Downloading and Building the Application

To clone or download this application from Github, go to the main page of this repository and then click Clone button to clone this repository or download as zip file. This content can also be downloaded using content manager by following these instructions.

Path of the application within the repository is apps/dmac/dmac_crc32_generate/firmware.

To build the application, refer to the following table and open the project using its IDE.

Project Name | Description
--- | ---
sam_d21_xpro.X | MPLABX project for SAM D21 Xplained Pro Evaluation Kit

## Setting Up the Hardware

The following table shows the target hardware for the application projects.

Project Name | Description
--- | ---
sam_d21_xpro.X | SAM D21 Xplained Pro Evaluation Kit

### Setting Up SAM D21 Xplained Pro Evaluation Kit

- Connect the Debug USB port on the board to the computer using a micro USB cable

## Running the Application

1. Open the Terminal application (Ex.:Tera term) on the computer
2. Connect to the EDBG Virtual COM port and configure the serial settings as follows:
   - Baud : 115200
   - Data : 8 Bits
   - Parity : None
   - Stop : 1 Bit
   - Flow Control : None
3. Build and Program the application using its IDE
4. LED indicates the success or failure:
   - LED is turned ON when the DMAC memory transfer is successful and hardware CRC values matched with the software calculated CRC value
     Following table provides the LED name:

     Board | LED Name
     --- | ---
     SAM D21 Xplained Pro Evaluation Kit | LED0

5. Observe output message in console as follows:
   - Expected CRC Value for the polynomial (0x04C11DB7) is (0xcbf43926)