Watchdog Timer in avr's

[EA7-JFV]

Hi, I'm trying to implement a reset routine in an AtMega328p,

The goal of routine is from the serial port, could command an reset of the atmega when I want to load a new software, through a bootloader

For that, I've think in willfully overflows the WDT, but I don't find any help in gcb about how to use wdt, only the #config WDT = ON, and in the posts of this forum, i found clrwdt (the compiler says error, and I substitute it by "asm wdr", but nothing more, and don't runs

Somebody has a example of use WDT in an Atmega?

Thanks to everybody

[Theo]

Manuel,

try the following code as basis for your program.
The code is based on the info in the ATmega328/P datasheet.
It's mandatory to keep the right sequence of code.

To check the code you are able to switch on/off the led by sending
led on or led off via the serial connection
By sending reset via the serial connection the microcontroller will reset.

Success, Theo.

'' Watchdog timer in reset mode

  #Chip mega328p,16

  #option explicit

 ' Setup Hardware Serial Port
  #Define USART_BAUD_RATE 9600
  Dir PORTD.0 In
  Dir PORTD.1 Out
  #Define USART_TX_BLOCKING

  ' This is mandatory to prevent unintentional time-out!
  ' Turn off global interrupt
  CLI
  ' Reset Watchdog Timer
  WDR
  ' Clear WDRF in MCUSR
  MCUSR = MCUSR AND WDRF
  ' Write logical one to WDCE and WDE
  ' Keep old prescaler setting
  WDTCSR = WDTCSR OR 0b00011000 ' WDCE = 1 , WDE = 1
  ' Turn off WDT
  WDTCSR = 0
  ' Turn on global interrupt
  SEI

  Dim MyString as String

  ; Setup Alive Led
  #Define LED PORTB.5
  Dir LED OUT

  repeat 3 ' Flash LED 3 times; meaning first part OK
    pulseout LED, 100 ms
    wait 100 ms
  end repeat

  Hserprint "Program started":HSerPrintCRLF

  Do Forever
        HSerGetString MyString  ' recieve string
        HSerPrint MyString  'echo received string
        HSerSend(13)
         If MyString = "led on" Then
             Set Led On
         End If
         If MyString = "led off" Then
             Set Led Off
         End If
         If MyString = "reset" Then
         ForceReset
         End If
    Loop


  Sub ForceReset
    CLI ' disable interrupts
    WDR ' reset watchdog timer
    WDTCSR = WDTCSR OR 0b00011000 ' WDCE=1, WDE=1
    WDTCSR = WDTCSR OR 0b01001000 ' WDIE=1, WDE=1, WDP3=0, WDP2=0, WDP1=0, WDP0=0
    SEI ' Enable global interrupts
  End Sub

[EA7-JFV]

Theo, I have seen your answer, I can weigh it in a few days because unfortunately these days I am very busy. In a few days, I answer you about the code you have kindly shared

Thank you very much, Theo!

[EA7-JFV]

Theo,
I just tried your code with a minimal adaptation to my app, and it runs great, fine!

Thank you very very much!!

[Theo]

Cheers, Manuel.
Enjoy Great Cow Basic!