The internal pullup is on the order of 20K to 50K Ohms. That is considered a "weak pullup" and with a long wire the input is susceptible to noise. A 1K pullup is a "strong pullup" and is much less susceptible to noise in the same circumstance.
The internal pullup is on the order of 20K to 50K Ohms. That is considered a "weak pullup" and with a long wire the input is susceptible to noise. A 1K pullup is a "strong pullup" and is much less susceptible to noise in the same circumstance.