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# 1.7 DBGU Ring Buffer

This example application shows how to use DBGU peripheral in Ring Buffer mode.

## Description

This example demonstrates read and write over DBGU using the Ring Buffer mode. The DBGU is configured in Non-blocking mode (interrupts enabled). The example asks the user to enter 10 characters. Once received, the characters are echoed back. In the process, the example demonstrates various ring buffer APIs.

## 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 be downloaded using content manager by following these instructions.

Path of the application within the repository is apps/dbgu/dbgu_ring_buffer_interrupt/firmware.

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

Project Name | Description
--- | ---
sam_9x75_curiosity.X | MPLABX project for SAM9X75 Curiosity Development Board
sam_9x75_curiosity_pro.X | MPLABX project for SAM9X75 Curiosity Pro Development Board

## Setting Up AT91Bootstrap Loader

To load the application binary onto the target device, the user needs to use at91bootstrap loader. Refer to the at91bootstrap loader documentation for details on how to configure, build and run bootstrap loader project and use it to bootstrap the application binaries.

## Setting Up the Hardware

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

Project Name | Description
--- | ---
sam_9x75_curiosity.X | SAM9X75 Curiosity Development Board
sam_9x75_curiosity_pro.X | SAM9X75 Curiosity Pro Development Board

### Setting Up SAM9X75 Curiosity Development Board

- Connect the UART DEBUG J35 on board to the computer using a UART-FTDI cable (to enable debug com port)
- Connect the USB port J2 on board to the computer using a micro USB cable (to power the board)

### Setting Up SAM9X75 Curiosity Pro Development Board

- Connect the UART DEBUG J63 on board to the computer using a UART-FTDI cable (to enable debug com port)
- Connect the port J1 on board to the computer using a Type-C USB cable (to power the board)

## Running the Application

1. Build the application using its IDE.
2. Open the Terminal application (Ex.:Tera term) on the computer.
3. Connect to the (USB to Serial) COM port and configure the serial settings as follows:
   - Baud: 115200
   - Data: 8 Bits
   - Parity: None
   - Stop: 1 Bit
   - Flow Control: None
4. The console displays the following message.
   - The console displays the initial transmit and receive buffer sizes
   - It then adds 10 characters, “0123456789”, to the transmit buffer and displays the available free space in the transmit buffer after the 10 characters have been added
   - The message asks the user to enter 10 characters
     Note: For this example, the “Free Space in Transmit Buffer = xx”, where xx can be anything between 117 to 127, depending on the USART baud rate and the CPU execution speed.
5. Enter 10 characters on the terminal.
6. Entered characters are echoed back on the console and message is displayed indicating that the receive notification is turned on.
7. For every 10 characters typed, it will be echoed back on the console.

Rev: E