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I am experimenting with low-power wireless arduino modules. For that, I needed 3V powered arduino so that I can do away with voltage regulators which eat up a lot of battery juice.

I am using 28 pin Atmega328p-PU dip IC with 8 MHz external crystal oscillator. Just for trying, I dumped the arduino pro mini 3.3V 8 MHz bootloader into it and it was a success. Everything is working as expected. However, I realized that SMD package which is being used in pro mini has 8 ADC pins compared to 6 in the DIP version.

Should I be worried about it?

Second feasible option is modifying the Arduino UNO board definition to use 8 MHz clock source as compared to 16 MHz and leave everything else same. Do you think this will serve my purpose?

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The Atmega328p has 8 analog inputs. Some packages (such as the DIP) don't have enough pins to bring all of them out, but they are in there. The SMD package brings all of them out, but it apparently the Pro Mini does not pick up two of them. The net result is the same - 6 useable and 2 unusable analog inputs.

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    At least the sparkfun Pro Mini has plated-thru holes for A4-A5-A6-A7. Some clones don't have A6-A7, and some have them located near the reset switch – James Waldby - jwpat7 May 12 '15 at 23:01
  • Then, I suppose there shouldn't be a problem with pro mini bootloader on 28 DIP. Thanks for solving the mystery. :) – Whiskeyjack May 13 '15 at 4:55

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