How do I change the frequency of an Arduino Nano?

Using Arduino Project Guidance
1

I am going to use an Arduino Nano for making a quadcopter Flight controller. The battery is a 1S 3. V Lipo whose voltage can range between 3.0-4.2 V. But the ATMega328p datasheet states that the minimum voltage for frequencies >10MHz is 4.5 V. And to keep things simple, I don't want to use any boost converter. So I want to clock it down to 8MHz using the internal oscillator.

How do I change the fuse bits? Do I need to do anything with the bootloader?

Or can I run at the low voltages instead? Will it cause any problem?

2

To run at 8MHz, reliably at lower voltage, you will need to burn the bootloader for 8MHz. I use the ArduinoISP sketch and the Minicore core. The Minicore core makes it easy to set the frequency and other options.

3

Abraar_Sameer:
So I want to clock it down to 8MHz using the internal oscillator.

If there is an external 16MHz oscillator on the Nano board I wonder will it need to be disconnected? Sorry, I don't know the answer.

...R

4

You do not need to disconnect the external 16mhz oscillator if using the internal 8mhz oscillator.

Be aware that serial comms may or may not work when running off the internal 8mhz oscillator - it's only calibrated to +/- 10%, and has significant variation with temperature and operating voltage. But in order for serial to work, it needs to be within +/- 2%. Most 328p's happen to be close enough to 8mhz at room temperature and 3.something volt supply that the speed falls within that +/- 2% range, but not all of them will.

You can buy 3.3v/8mhz arduino pro mini's which use an external 8mhz oscillator to guarantee that the clock will be accurate enough for serial to work (these are also better than a nano for use in a quadcopter because the serial adapter is not on the board, so a pro mini is lighter than a nano)

That all said, experience (both mine and the forum in general) has found that '328p's will typically work at 16mhz and 3.3v, at least at room temperature, even though this is out of spec.

5

DrAzzy:
Be aware that serial comms may or may not work when running off the internal 8mhz oscillator

I have built several breadboard 328s working off the internal 8MHz oscillator and I have never had a problem. Of course that is not the same thing as converting a Nano.

...R

6

Robin2:
I have built several breadboard 328s working off the internal 8MHz oscillator and I have never had a problem. Of course that is not the same thing as converting a Nano.

...R

I've got one that works at 3.3v, but not at 5v - but it has also been my experience that the vast majority of '328p internal oscillators are good enough for serial at 3.x volts at close to room temperatures.

7

groundFungus:
To run at 8MHz, reliably at lower voltage, you will need to burn the bootloader for 8MHz. I use the ArduinoISP sketch and the Minicore core. The Minicore core makes it easy to set the frequency and other options.

The MiniCore core was the perfect of all, it needs to be more popular