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Author Topic: Pins pulse during autoreset  (Read 1634 times)
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Hi all,

I've noticed an issue when autoreset occurs where the pins 'pulse' which is causing me some problems. Note, when I start the arduino normally, this 'pulsing' doesn't seem to occur, but only when I connect a USB cable, click on the 'Tools' menu or when I close the 'Serial Monitor' in the IDE.

Is there a way to not have the pins pulse?
(This is in follow up to the thread: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1295273279/3#3)

The problem is that I'm using ArduinoAndy's PLC watchdog as a safety circuit. (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267907942/0). However, when this 'autoreset' problem occurs, the pins pulse, causing my watchdog to be enabled...which in my case would try and turn on various LPG burners and fans and water pumps. Obviously this is not ideal. smiley-wink

So, to the question: Is there a way to NOT have this 'pulse' occur during auto-reset.

Note:
The problem doesn't occur if I manually reset.
The problem doesn't occur during normal power up.
The problem only seems to occur during this 'auto reset'.

Obviously going through and disabling auto reset _could_ be construed as a solution, but I'm a little worried that there's something more sinister going on here...

I have tried this on 2 Dieceimila's and both operate exactly the same.

Any help appreciated...
Craig.
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Please provide a complete circuit for one of the pins that "pulses".
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The problem doesn't occur if I manually reset.
The problem doesn't occur during normal power up.
The problem only seems to occur during this 'auto reset'.

Obviously going through and disabling auto reset _could_ be construed as a solution, but I'm a little worried that there's something more sinister going on here...

Your suspensions are justified. An auto-reset should not behave any difference then manually pushing the reset button. Not sure what might be causing your symptoms. A typical response might be to post your wiring and code, but maybe someone else has a simpler clue or explanation?

Lefty
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Update:

After triple checking what's going on, I removed the 'watchdog' pins from the board (so there's no chance of a signal arriving from the arduino) and the problem still happens.

It appears that the problem occurs as part of a power supply fluctuating (I'm connecting the watchdog board to Vin, temporarily).

Note: there is obviously an issue, but not due to the output pins themselves. I'll try some caps across the the supply (Vin to Gnd) to see if that alleviates the problem....

As I mentioned earlier, I am using ArduinoAndy's circuit: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267907942/7#7, Unfortunately, I didn't put any smoothing caps across the power supply as his circuit has.
« Last Edit: January 19, 2011, 06:18:47 pm by cmroanirgo » Logged

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Update 2:

Hi again, it appears to be definitely related to Vin fluctuating during auto reset. By putting a cap (I used 100uF, the largest I had) across Vin to Gnd the problem is gone.

Unfortunatey, I don't have a CRO/DSO to verify this.

Thankfully, in the 'real' environment I won't be using Vin from the board, but an externally powered supply.

Unfortunately, when I put my watchdog pins back in, the board resets as per my first post.

This could be due to my el-cheapo wall wart that I'm using temporarily, or something else. Here's my schematic:

Note that +12v is going to Vin...

Craig.
« Last Edit: January 19, 2011, 06:39:20 pm by cmroanirgo » Logged

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Here's my schematic:

edit: here's a link to the schematic: https://lh6.googleusercontent.com/eH8iAbfY7BeKzp00FaPoUjfQxBqye-vlE2nyBBLinZO8huvsfr97qznjtJIBjqlZBW4-X2VVABRg8B74fJB15GKiUA=s5125
« Last Edit: January 19, 2011, 07:35:06 pm by cmroanirgo » Logged

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Update 3:

After adding a cap (10uF) across my watchdog reset (pin smiley-cool to gnd, my system no longer has any problems with the auto reset/usb connection issue.

I must state that I'm a little concerned that the arduino pins can pulse at all unless explicitly told to.
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I must state that I'm a little concerned that the arduino pins can pulse at all unless explicitly told to.

Part of the reset process, regardless of it's cause, all I/O pins are changed to input mode and are in tri-state, i.e. floating. The bootloader will setup and initialize whatever pins it uses, 0,1 &13 for sure. Only after the bootloader times out and jumps to your sketches code will/can the I/O pins be initialized to your desired condition.

Don't know if that helps you, but it is the process as I understand it.

Lefty
« Last Edit: January 19, 2011, 09:32:00 pm by retrolefty » Logged

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sorry about that...
try this (different servers smiley-wink )
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