My Propeller keeps resetting - why?

13 months ago by
I have built my first Propeller circuit and copied the example on page 17 of the Manual exactly.

I can download my program into the EEPROM with my PropPlug and it runs fine, but when I remove the PropPlug the circuit becomes unstable.  It seems to be resetting itself all the time.

What have I done wrong?

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Community: Parallax

1 Answer

13 months ago by
This is a common problem for those new to the Propeller.
There is an unfortunate omission in the Manual's example circuit diagram.

Try adding a 10,000 Ohm resistor between pin 12 (VDD) and pin 11 (RST).

This is commonly known as a "pull-up" resistor.  In a nutshell, without the PropPlug attached, the RST pin is in a "floating" state, meaning that is subject to electromagnetic interference which can easily cause your Propeller to reset itself.

The pull-up resistor prevents this floating state (by literally pulling the voltage on RST up to near 3.3 Volts) which prevents resetting.
According to the same manual with BOE tied low RST already has an internal 5k (pull-up) resistor. Are you saying that's not enough?
written 13 months ago by kuroneko  
In my experience RESn can still be sensitive and glitchy.  I tend to use 4k7 or 10k resistors and have not had further problems.
written 13 months ago by Woss Code  
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