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# 1.18 SERCOM SPI Blocking

This example application demonstrates how to use the SERCOM SPI peripheral to transmit and receive a block of data in a blocking manner.

## Description

This example shows the transmit and receive operation over a SPI interface in a blocking manner. The CPU polls the peripheral register continuously to manage the transfer. It transmits an array of values and verifies the value transmitted by receiving the values back with loop back and comparing it to the value transmitted. The loop back test requires the MOSI output pin to be connected to the MISO input pin so that anything transmitted will also be received.

## 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/sercom/spi/master/spi_self_loopback_blocking/firmware.

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

Project Name | Description
--- | ---
sam_d20_xpro.X | MPLABX project for SAM D20 Xplained Pro Evaluation Kit

## Setting Up the Hardware

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

Project Name | Description
--- | ---
sam_d20_xpro.X | SAM D20 Xplained Pro Evaluation Kit

### Setting Up SAM D20 Xplained Pro Evaluation Kit

- Use a jumper wire to short pin 16 and pin 17 of the EXT2 header
- Connect the Debug USB port on the board to the computer using a micro USB cable

## Running the Application

1. Build and Program the application project using its IDE
2. LED indicates the success or failure:
   - The LED is turned ON when the value received matched with the transmitted value
   - The LED is turned OFF when the value received did not match with the transmitted value
3. SPI data transfer and compare match checking happens only one time

Following table provides the LED name:

Board | LED Name
--- | ---
SAM D20 Xplained Pro Evaluation Kit | LED0