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Topic: exteral watchdog timer ic for mega2560 (Read 2 times) previous topic - next topic

jm_wsb

Hello,

I have build a home automation arduino circuit with ethernet, SD logger, whireless RF12 transmissions over nodes, LCD display. So my master arduino is mission critical and crashes ones in a month. (always when requesting tcpip packages)

as I can't get the internal wdt for atmega2560 (on standard mega board) to work (due to restrictions of the bootloader)
and I cant flash the bootloader (I did not find a very good explanation).

So my only option is to use an external watchdog timer ic.
Has anyone got experience with it ?

Thanks in advance,
Jeroen.

Coding Badly


jm_wsb

Yes, I have another one, but just for the power consumption and the space, I would like to use a small chip.
But this could be also an option.

Jeroen

Coding Badly

You misunderstand.  You can use the second Arduino to reprogram or even remove the bootloader from the home automation Arduino.  The second Arduino acts as an in-circuit serial programmer allowing you to change the home automation Arduino anyway you wish...
http://arduino.cc/en/Tutorial/ArduinoISP

bigfun

a few days ago, i found myself needing a watchdog without evening knowing there was such a thing and that it had a name.  my initial plan was to hook up two 555 timers (actually, two such timers in a 556 package), using one as a missing pulse detector and the other as a brief one-shot (it would have to work through a logical inverter).  i'd dedicate an arduino pin to sending regular pulses to the missing pulse detector, and if that ever failed, i'd fire the one shot, which would strobe the reset pin through the inverter.  it wouldn't be difficult to implement and wouldn't require a special bootloader. but then i discovered that watchdogs are real things and are implemented in hardware on atmel chips.  the tricky part was getting past the stock bootloader, which is inherently incompatible with the built-in hardware watchdog. if i were in your position and gave up on the bootloader, i might implement the dual 555 analog watchdog.

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