AVR-Chat

On Oct 17, 2012, at 8:38 PM, R E Purcella wrote:

> the Atmel documentation calls for higher value pull up or pull down 
> resistors, usually 20K. however 10K work fine. But 1K is a bit low.

Unless the AVR pin is driving the resistor, high or low, it doesn't matter to the AVR how low the resistor is.  If the resistor is too low the device driving it may not be able to pull it low enough or it may be overloaded.  The other factor is how much power the resistor dissipates.  1K used to be a common value as a pull up resistor but it's 5 mA (Vcc = 5V) may well be more than the rest of the circuit.

I have been using either an external 100K resistor or the AVR built in pull up of 30K.




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