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You can get them cheaper on ebay (No minimum charge, no excessive shipping) if you can weight about 2 week. 1N4728 A couple of them are at 1.22 buy it now free shipping for 10. You could even use the best offer and try to get them down to 99 cents. There's currently an auction for 30 3.3v Zeners (1/2watt instead of 1watt though) but no part number for 1.49 or best offer. Ebay is often the best for one-off part orders. Unless you are ordering 15+ dollars worth of parts, shipping from web-stores hurt.

You can use any P1.x pin as long as you configure it to ADC.* The extra components there are for voltage limiting (zener diode) and keeping the pin voltage from floating when there is no voltage from the peizo (pull-down resistor).* The Arduino is a 5v device and accepts 5v logic. The MSP430 is a 3.3v device; 5v logic could damage the MSP430. Replacing the zener with a 3.3v version will limit the output to 3.3v (anything higher will be shunted to ground through the zener diode). Using the 5.1v zener could allow a damaging voltage level (5.1v) to your MSP430.* *Note: I'm no