http://arduino.cc/en/Tutorial/ArduinoToBreadboard#.UwD6jX-9KSM In this example, could the 10K resistor be omitted if the Arduino ISP sketch was modified to set the reset pin high on the chip to be burned, rather than the resistor pulling it high. Would the Arduino not act as the 10K pull-up resistor? There'd be the issue of current limiting which the 10K resistor does, but wouldn't the Arduino doing the boot loading limit it's output, and with the whole process just taking long enough to burn a boot loader... Maybe the 10K is definitely needed? Anyone know for sure? Thanks.
for modern arduinoisp the resistor serves no purpose during isp programming. for uploading via serial, depending on vcc and level of the dtr signal, the 10k resistor can be eliminated there too. the internal avr one is sufficient. all mine work fine w/o. for cases with mismatched voltage (ie 3v ftdi w/5v avr) a 10k to 3.3v works every time so considering how cheap they are it dont hurt to tack one on.
well if you just scroll down a bit, you’ll find a “minimum circuit” that don’t even have a xtal and capacitors.
if you’re just going to upload the sketch or bootloader, you don’t need the 10k ohm resistor.
but if you want to run the target avr after you unplug all the wires to your arduino, you’ll want that 10k res (instead of connecting RESET directly to VCC) anyway.
It’s recommended by Atmel to have it, in some environments it’s more important than others.
Palatis: well if you just scroll down a bit, you'll find a "minimum circuit" that don't even have a xtal and capacitors.
in my minimum mega8 ardiunoisp design, except for pwr bypass, there are no external components at all. so far ive built several dozen of these for others with no problem. also with modern crystals and proper fuse settings theres less reason for those two caps there.
Palatis: but if you want to run the target avr after you unplug all the wires to your arduino, you'll want that 10k res (instead of connecting RESET directly to VCC) anyway.
i disagree. for some reason builders, specially hobbyists, like to attach as many unnecessary components as possible. in the case of reset circuit it often creates far more problems than it solves. in particular throwing in caps which turns out to be a major reason nooby circuits wont program.
imo NOTHING is the best thing to hook up to that pin. as long as you dont go around poking it with metal tools or place megawatt welder 1" away problems are rare. of course, as always, for mission critical applications its best to adhere to atmel specs to the letter. not so much for technical but rather liability reasons.