stamp resets when reconnecting to PC

MTompson

I am running a program that I periodically check some numbers I'm sending out to DEBUG. I wanted to get rid of my LCD I had hooked up and simply use the DEBUG to check my numbers. The trouble is when I reconnect my board to my PC (via serial D9 to USB adapter) the program resets on the stamp! Any ideas on hard wiring any pins to stop this happening? Many thanks....

MTompson

I did find this on the web:

Unwanted resets from noise on the serial port ATN line
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Unwanted resets can occur when there are noise sources like motors or radios near the Stamp. Also, these resets can occur when the serial programming or data cable remains connected. Noise is coupled in through the sensitive ATN signal on physical pin 3 of the Stamp, pin 4 on the DB9 connector.

I always put a 3.3kohm resistor and a 0.1uF capacitor in parallel with the ATN input. That's BS2 pin 3 to ground. found on pin 4 of the stamp. This usually cures the unwanted "reset" problem. It lowers the pin's input impedance from 20k down to 3k and filters short spikes. A capacitor in series with ATN can still be used to reset or wake up the system.

DB9S ---||

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;

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/\/\/---;
pin4 0.22 | 3.3k |
optional |

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| 0.1 |
atn ground

webpage: http://www.emesystems.com/BS2rs232.htm#resets

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I don't have a radio or any motors (although I intend to later) I am however using maths coprocessor and a realtime clock.

Chris Savage

What you're experiencing is normal. The only way to prevent the Stamp Module from being reset would be to disconnect the ATN pin from connecting to the PC. This has been done in the past by using a socket and removing that pin from the socket. You then plug your BASIC Stamp Module into the socket and the socket into the one on the BoE (or whatever board you're using). This allows debug communication without resetting the Stamp Module, however you cannot program or ID the Stamp Module without removing the socket again. I hope this helps. Take care.

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Chris Savage

Parallax Engineering
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sumdawgy

Heh, i was just about to ask the same question.

Hrm...now to decide plan to fix.....

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Before you criticize someone, walk a mile in his shoes. That way if he gets angry, he'll be a mile away and barefoot. - unknown