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Topic: two 328P with one crystal or resonator (Read 1 time) previous topic - next topic


Someone on here was talking about doing this recently by just connecting the same crystal to both chips.  IIRC, you leave Xtal2(?) unconnected on one of them.  The idea being that whichever pin it was is used to kick-start the oscillation, so you only needed one of the ICs to do that.

Not sure if that worked out for them, or if this is even sound engineering, but there was a discussion on it.  I think the topic was something about designing a "dual-core" Arduino.


You can use CLKO (=PB0) from the 1st chip to drive XTAL1 (=PB6) on the 2nd - in which case the crystal or resonator can be low-power.

You can also use XTAL2 (=PB7) from the 1st chip to drive XTAL1 (=PB6) on the 2nd - in which case the Full Swing Crystal Oscillator should be configured.


CrossRoads did this with one of his recent designs. Ask him or find his posts.


I only designed it, didn't actually build. Be easy enough to add a 2nd socket & processor to my wirewrap test board & try it out.
dual 328
dual 1284
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.


If I remember tonight, I'll drop a couple of 8As on a breadboard bunking up with a single resonator and see if the smoke stays in.

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