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Topic: Circuit for Atmega2560 (Read 568 times) previous topic - next topic

tsaG

Hi!

Im planning to do my own circuit with an Atmega2560. I tried this with an 328 before, but there are some differences.

1. The Reset Circuit. On the 328, the Reset is held high by an 10k Resistor. In the 2560 Circuit there is none.
2. Do I need two 22pf capacitors for the oscillator circuit?

regards

Pat

retrolefty


Hi!

Im planning to do my own circuit with an Atmega2560. I tried this with an 328 before, but there are some differences.

1. The Reset Circuit. On the 328, the Reset is held high by an 10k Resistor. In the 2560 Circuit there is none.
2. Do I need two 22pf capacitors for the oscillator circuit?

regards

Pat


If you look carefully at the arduino R3 2560 mega board schematic you will find the reset circuitry at the top, just right of center, of the drawing, comprised of a pull-up resistor, a bypass capacitor and a diode.
http://arduino.cc/en/uploads/Main/arduino-mega2560_R3-schematic.pdf

If you are going to use a two terminal crystal resonator then yes the padding capacitors are required to maintain accurate frequency and reliable start-up. If you use a three terminal ceramic frequency resonator then you do not need external padding caps as they are built in to the package.

Lefty

oric_dan

Use the crystal and (2) 22 pF caps, forget about ceramic resonators.

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