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# 1.22 PIT Period Change

This example application shows how PIT period can be changed during run time.

## Description

The LED starts blinking at one second intervals. When the switch is pushed the timer is stopped. When the switch is pressed again, the period is cut in half and the timer is restarted. The timer is turned off and on every alternate switch press. When the timer is started on every alternate switch press, the period is toggled from 0.5 second, 0.25 second intervals, 0.125 second intervals and 1 second intervals. There is no debounce in the switch so it is possible that pressing the switch will jump more than one interval.

## 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/pit/period_change/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. LED toggles every 1000 ms.
3. Press switch to stop the timer and, therefore the LED toggle.
4. Pressing the switch again starts the timer and changes the rate of LED toggle.
5. The application alternates between step 6 and 7 on each switch press.

Refer to the following table for Switch and LED names:

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

Rev: E