thought he might have to start cutting the pin itself off but fortunately non-plated hole solved it.īottom line there is virtually no difference between the 20k-30k internal pullup and popular but pointless 10k external for rf pulses unless you go down to 50ohm or so. i was hired to solve this problem in a welding application and even a pad for that pin proved problematic. resistor lead, or short pcb track can act as antenna for noise. generally has little effect and some cases more harm than good. This is correct but old wives tales persist about the need to add circuits to reset. If you connect nothing to it, it is extremely unlikely to be affected by outside influences. Has an internal pull-up of a certain effective impedance. Given that the internal pull-up is not closely specified (as others have noted), the resistor provides a guaranteed reset pulse length.

The reset pulse must be sufficiently brief that the chip can start the bootloader again. The latter in particular is the reason for the pull-up. The DTR line of the USB interface (via a capacitor).Why is there a pull-up resistor on reset on my Uno?īecause the Reset pin is connected to three devices: If you are wearing the specified wrist strap (which I suspect very few of us here, do) and have carefully avoided synthetic fabrics, then you are quite unlikely to cause such a problem. If you are in a highly static-conducive environment - dry and insulated by synthetic fabrics, then it will be easy to produce such impulses by touch. That possibility is proportional to the length of such an antenna and the source of such impulse. If however, you connect an antenna - being a wire or trace of any length - then there is a possibility of picking up impulses. The reset pin - or indeed, any I/O pin which you are monitoring with INPUT_PULLUP - has an internal pull-up of a certain effective impedance. No point having a pissing contest about it.

Pull the pin challenge 15