Asked — Edited

Watchdog Timer Ez-Board

Greetings, does anyone know(DJ Sures) if the EZ-Board has a watchdog timer and is accessible? There are EZ-Board critical applications like Josh Starnes aquarium. It would be really beneficial to know if the Ez-B is not functioning. Richs battery monitor is a great script to help with board monitoring! A separate hardware board as a watchdog wired to a light or alarm would be perfect. :)


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Last bump to the top!:) enquiring minds! I checked the hardware specs to no avail....but someone else with more intimate knowledge of the chip may know :)

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I was writing a post earlier at work but got called away. I have an idea but need to check it out first, bear with me on this one :)

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OK, so I just checked out what I thought was the case and it is right.

Basically, the EZ-B sets all digital signals to low when connected and after disconnection (slight delay). So we can use this to power a circuit that will alarm when disconnection occurs.

There is also a script command IsConnected. We can have a looping script that watches this and reconnects on disconnect or alerts through the PC in some way.

Both solutions I will look into further now that I know they work.

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A quick (and rough) video. I didn't have time to edit it or type up the description so for a change I spoke it.

We can use this to control a circuit that gives a connected LED (if required) and a fault/disconnected LED and/or buzzer. I will work out the circuit to do that, a simple transistor based circuit should work, unless anyone else wants to jump in and pop up a schematic.

Afterthought: Connection between VCC and Signal may work if low is the same as ground (will have to check, it could also blow up the EZ-B for all I know).

Edit: Yes it worked. Which means a simple modification to the TIP circuit and we are in business. I will knock up a test circuit on a bit of proto board when I get the chance.

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OK, nice and simple circuit to illuminate an LED on disconnect. I have just tested it and it works great.

So simple to do. All you need to do is connect an LED between VCC and Signal of an unused digital port on the EZ-B. When it's disconnected the port goes low and current flows through the LED to indicate that a disconnection has occurred.

On connection you just need to add the following line to your init script or the Connection Established Cmd;


Substitute D0 for whichever port the LED is connected to is on.

Now, on connection the command will set the signal to high and current will not flow through the LED.

You could also add an LED across Signal and Ground, this would work the opposite way, so the LED would illuminate on connection established and turn off if connection is lost.

I plan to knock up a better board over the weekend so I can do a video of this. I also plan to make another circuit which would be capable of sounding a buzzer for an audible alert.


HOLY AWESOME RICH ! Thank you so much! That answers my question and MORE! and for the need to know hardware people...yes the chip has a Watchdog timer specifically "In addition to their Power-up and Oscillator Start-up Timers provided for Resets, PIC18F2682/2685/4682/ 4685 devices have a Watchdog Timer, which is either permanently enabled via the Configuration bits or software controlled (if configured as disabled)......BUT Thread question is NOT intended for anyone to pursue ! This Forum is about how EZ it is thru EZ-Builder to enliven your robot! :)

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You could also add a third LED across any VCC and Ground, or from the expansion ports. On power-up of EZ-B the LED will illuminate.

Additionally, you could extend the EZ-B blue LED to display board status.

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To expand, since in the Squeegy topic power cycling was mentioned. I would imagine this could be possible using a small microcontroller such as the ATtiny2313 and some transistors programmed that when one of the pins goes low the power to the EZ-B is interrupted for a few seconds and then re-enabled causing a power cycle and therefore (hopefully) resetting the EZ-B.

I do not know enough about the ATtiny2313 at the moment to produce any kind of schematic but if anyone else has ideas then a bit of brainstorming here would be great.

From the above we know we can have a pin go high on connection and low on disconnection. A simple circuit using a mosfet and a couple of NPN transistors can create a latching power circuit using a simple push to make momentary switch (I have a crude schematic of this at home, I will provide it if needed) which may be of use?

All ideas are welcomed :)