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I just programmed my Atmega328p with an Arduino as ISP. I am making a permanent circuit on a piece of perf-board. I need to connect the Nokia 5110s Vcc pin to 3.3V on the Atmega328p. Which pin is 3.3V because there are two positive pins and I'm not sure which one gives 3.3V and I'm not sure if they are both input (I need output). Can someone please tell me which pin is 3.3V output on the Atmega328p?

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    \$\begingroup\$ ATmega328p is a single chip micro-controller. The 328P does not have a 3.3v output. You might be confused by the AVCC pin, which is an input for the A/D converter system. Vcc (3.3v) would be connected to the ATmega328p pin 7. \$\endgroup\$ – Marla Feb 21 '16 at 15:28
  • \$\begingroup\$ and then if I want to give 3.3v to the screen aswell do I connect it to he battery or to the + terminal on the 328p? \$\endgroup\$ – user2279603 Feb 21 '16 at 15:36
  • \$\begingroup\$ If battery is 3.3 volts, then both the 328P and the Nokia display would be connected to battery. If battery is higher than 3.3v, then you will need an additional 3.3v regulator. The 328P could take 5 volts, but the logic of the Nokia must be 3.3v Don't try to run the 328P on higher volts. The 328P and Nokia should both use 3.3v \$\endgroup\$ – Marla Feb 21 '16 at 15:43
  • \$\begingroup\$ What is your battery voltage? \$\endgroup\$ – uint128_t Feb 21 '16 at 16:20
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Atmega328p doesn't have any output voltage, it only has input voltage, VCC and AVCC must be the same, AVCC should be connected to VCC via LC filter.

The easiest way how to connect the Nokia 5110 display is to power both uC and display from 3.3V

You said you use Arduino as ISP, make sure you use 3.3V arduino as well for this, or get a ICSP level shifter

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ATmega328p is a single chip micro-controller. The 328P does not have a 3.3v output.

You might be confused by the AVCC pin, which is an input for the A/D converter system. Vcc (3.3v) would be connected to the ATmega328p pin 7.

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And this information is from the Nokia Display Data Sheet

enter image description here

In addition to your 3.3v for the logic, you will also need voltage of 6 to 8.5 volts for the Nokia LCD.

So it sounds like what you really need is a battery of at least 6 volts, maximum of 8.5 volts. And a 3.3v regulator for the logic of the Nokia and the 328P.

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Both Nokia LCD and ATmega238P could work on 3.3V so you should provide the same voltage you are using for MCU. You are probably reading some Arduino tutorial so you connect LCD to power supply of Arduino. If you are plan to use ATmega328p alone, that power supply you need to provide.

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