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View Full Version : OEM BS2 - Rev A1 - Cause Reset if Remove Serial Cable which connect thru Prolif



CGTan2020
09-02-2008, 07:41 PM
All,


I have a OEM BS2- Rev A1, it is program thru a USB Serial Port from Prolific, whenever I remove the USB port with the OEM BS2 Rev A1 connector at the other end, it will cause a system reset of the Basic Stamp. Anyway to prevent that from happening?


best regards,

CGTan

Chris Savage
09-02-2008, 09:50 PM
Probably not without physically disconnecting the DTR line from the DB9, perhaps with a switch. Have you tried unplugging the serial side first? What is happening now is that when you disconnect your cable the DTR line is getting toggled briefly which is causing the reset.

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Chris Savage
Parallax Engineering

CGTan2020
09-03-2008, 05:15 AM
I have yet to try. Does the FTDI chips also behave that way? Yes, the DTR does get toggled briefly. How to prevent the DTR from toggle and cause the rest?

CGTan

Beau Schwabe (Parallax)
09-03-2008, 09:17 AM
CGTan2020,

You can try placing a 1K or so resistor between the DTR pin and Vss. This will effectively attenuate the DTR signal. It depends though on how the USB Serial Port from Prolific deals with this signal. If it's a passive capacitor reaction due to unplugging the USB Serial then the 1K resistor will probably work fine... if the "brief toggle" is active or driven in any way it may not work.

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Beau Schwabe (mailto:bschwabe@parallax.com)

IC Layout Engineer
Parallax, Inc.

CGTan2020
09-03-2008, 09:50 AM
I will try out, many thanks