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# 1.11 FLEXCOM USART Flow Control

This example application shows how to use the FLEXCOM module in USART flow control mode.

## Description

This application configures FLEXCOM3 in non-blocking mode and FLEXCOM1 in blocking mode. FLEXCOM3 is used for data transmission and FLEXCOM1 is used for receiption. The TX line of FLEXCOM3 is connected to the RX line of FLEXCOM1. The RTS line of FLEXCOM1 is connected to the CTS line of FLEXCOM3. FLEXCOM3 transmits 100 characters using interrupts. Application however simulates a slow receiver by inserting a delay after each character is read on FLEXCOM1. As a result, once the RX FIFO is full, the RTS line is de-asserted and transmitter (FLEXCOM3) stops sending the data. Eventually, when the receiver reads out sufficient number of bytes from the RX FIFO, such that the number of bytes in the FIFO goes below RXFTHRES2, the RTS line is again asserted and the transmitter continues sending the data. The demo application indicates success if the received data matches the transmitted data.

## 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/flexcom/flexcom_usart_flow_control/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

## 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

### 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)
- Make connections as following:
  - Short PIN 6 (PC22, FLEXCOM5 TXD) on mikroBUS connector to the PIN 14 (PA29, FLEXCOM1 RXD) on mikroBUS connector
  - Short PIN 5 (PC23, FLEXCOM1 CTS) on mikroBUS connector to the PIN 13 (PA28, FLEXCOM1 RTS) on mikroBUS connector

## Running the Application

1. Build the application using its IDE
2. LED is turned ON on success.

Refer to the following table for LED name:

Board | LED Name
--- | ---
SAM9X75 Curiosity Development Board | RGB_LED (Green)