1.6 DWT Timeout

This example application shows how to generate a Dual Watchdog timer reset by simulating a deadlock.

Description

This example application configures Programmable secure dual watchdog timer (PS-WDT) to run in window watchdog mode. Watchdog period is 4 seconds, with 1 second repeat threshold and 3 second level threshold. Two switches are used to simulate deadlock and repeat threshold violation. Blinking LED simulates a normal process. When the application is run, the watchdog is cleared after every 2 seconds.

Pressing switch 1, will emulate a deadlock by not clearing the watchdog. LED will remain turned on. 3 seconds after previous watchdog clear, level interrupt will be generated. 4 second after previous watchdog clear, MCU will be reset.

Pressing Switch 4 will result in a watchdog clear, if the repeat threshold have not elapsed since the previous watchdog clear, this will result in a repeat threshold violation interrupt. Pressing Switch 4 twice in quick succession will result in a guaranteed repeat threshold violation.

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/dwdt/dwdt_timeout.

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

Project NameDescription
sam_a7d65_curiosity.XMPLABX project for SAMA7D65 Curiosity Board

Setting Up AT91Bootstrap Loader

To load the application binary onto the target device, we need 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 NameDescription
sam_a7d65_curiosity.XSAMA7D65 Curiosity Board

Setting Up SAMA7D65 Curiosity Board

ADDITIONAL HARDWARE REQUIRED
  • SD Card with FAT32 file system
SETTING UP THE SD CARD
  • Download harmony MPU bootstrap loader
  • Copy the downloaded boot loader binary( boot.bin) onto the SD card
SETTING UP THE BOARD
  • SDMMC slot used for bootloading the application is SDMMC1 (J10)
  • Connect the USBA port J3 on the board to the computer using a Type-C USB cable (to power the board)
  • Connect the UART Debug port (J35) on the board to the computer using a FTDI-USB cable

Running the Application

  1. Open the Terminal application (Ex.:Tera term) on the computer
  2. Copy the output binary (named ‘harmony.bin’) onto the SD Card (Refer to the ‘Setting up hardware’ section above for setting up the SD card)
  3. Insert the SD card into SDMMC slot on the board
  4. Connect to the Virtual COM port and configure the serial settings as follows:
    • Baud : 115200
    • Data : 8 Bits
    • Parity : None
    • Stop : 1 Bit
    • Flow Control : None
  5. Build and run the application using its IDE
  6. Console should show the following output and LED1 should be blinking
  7. Press Switch 2 to emulate a deadlock
  8. Console output is updated as follows and LED2 starts blinking:
  9. LED2 stops blinking and “RomBOOT” is printed on the console indicating a processor reset
Refer to the following table for Switch names for different boards:
BoardSwitch 1LED 1LED 2
SAMA7D65 Curiosity BoardSW2RGB LED (Blue)RGB LED (Red)