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I would like to set up a project with an ATtiny chip, such as the ATtiny84 or ATtiny85, in which I interface the microcontroller directly with an XBee for both wireless serial communication, as well as monitoring a digital signal from the Xbee (digital input to the ATtiny). As the Xbee chips can handle only 3.3V and will be damaged at higher voltages (such as 5V), I was wondering whether I can simply power the entire project at 3.3V so that all digital inputs and outputs will be at that voltage?

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Yes. As given in the datasheets, normal ATtinyX4/X5 chips can run with a supply between 2.7 and 5.5V inclusive, whereas the low-power versions can run between 1.8V and 5.5V. Mind the speed restrictions when running at lower voltages though; see the "Electrical Characteristics" section of each datasheet to determine the maximum characterized speed for a given voltage.

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  • Won't less speed affect serial communication? Isn't there an option in the bootloader or somewhere to fix this? – Anonymous Penguin Jun 14 '14 at 17:35
  • Sure it will, which is why you adjust your timing mechanism appropriately. – Ignacio Vazquez-Abrams Jun 14 '14 at 17:43
  • Thanks for the comments. Does that mean that when I use 3.3V as the supply voltage that the pin voltages, e.g. the HIGH signal of a digital output will be the same 3.3V? – hobie Jun 16 '14 at 10:37
  • It will be very close. See the datasheets for details. – Ignacio Vazquez-Abrams Jun 16 '14 at 10:53
  • Specifically, table 21-1 says that V_OH is going to be at least 2.5V for a 3V power supply, so maybe 2.7V for a 3.3V supply. That should provide a sufficient safety margin for the input stage of 3.3V logic. – microtherion Mar 9 '15 at 23:28

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