ICSP

RESET_BUTTON

ATmega328P

The main processor of the Arduino Nano is the 

 microcontroller in 32-pin quad flat package (VQFN). The letter 'P' in the microcontroller's name is for Picopower, referring to the fact that it has less power consumption than the ATmega328 which is used in 

. Otherwise, their technical specifications are the same.

Arduino Uno Rev3

Arduino Nano Microcontroller

The ATmega328P Microcontroller

The reset button can be used to restart the microcontroller or to put it into bootloader mode for uploading new sketches. It has the same effect as connecting the 

Unique

Arduino Nano Reset Button

Reset Button

The ICSP header is intended for programming the board with an external programmer. It's another way of programming the board. You can connect a programmer board (a dedicated hardware) to these pins and transfer your firmware to the board via that. You can also use another Arduino board as a programmer. It's mostly used in cases where you can't program the board using USB via Arduino IDE.

Arduino Nano ICSP Header

ICSP Header

The board has a USB Mini B port, which can be used for programming the board as well as providing power to the board. Also when the board is connected to the computer, any data transfer via Serial library is done via this connector.

Arduino Nano USB Port

USB Port

The board has 4 builtin LEDs of which 1 is accessible in code:

TX LED: Turns on whenever the board is transmitting data via USART through USB connector.

RX LED: Turns on whenever the board is receiving data via USART through USB connector. 

Power LED (Labeled "ON"): Stays on as long as the board is powered (obviously)

 pin. It can be toggled on or off by setting that pin to HIGH/LOW correspondingly.

Digital

Here is the Blink example code provided by Arduino IDE that turns the on board LED on and off every second. As you can see, the 

 is a constant that contains the pin number that is connected to the built-in LED of the board. In Arduino Nano, the value of 

Arduino Nano LEDs

LEDs

Arduino Nano comes with a USB To Serial converter chip on the back of the board. When sending or receiving data via 

 pins, they go to this chip and get converted to the USB protocol and vice versa. This allows your program on the board to communicate with the computer via serial interface and abstract away the USB protocol completely.

USART

Arduino Nano USB to Serial Converter Chip

Arduino Nano USB to Serial Chip

USB_TO_SERIAL_CHIP

USB To Serial Converter Chip

The Arduino Nano is a compact and powerful development board designed for hobbyists, students, and professionals alike. Based on the ATmega328 microcontroller, this board is a smaller and more affordable version of the popular 

 board. Despite its smaller size, the Arduino Nano packs a punch with its powerful features and wide range of capabilities featuring:

Wide range of input and output pins, including 14 digital I/O pins of which 6 are PWMs

32 KB of Flash, 2 KB of SRAM and 1 KB of EEPROM

USB Mini B connection for programming and power

ICSP header for programming with an external programmer

Support for all known communication protocols like UART, SPI and I2C

The Arduino Nano is a great choice for projects that require a small, portable, and low-cost microcontroller board. It is well-suited for projects such as controlling motors, reading sensors, or controlling LEDs.

In this section we review the board pinout and will have an overview on its physical properties as well as major components on the board.

Arduino Nano Dimensions

Arduino Nano Digital Pins

Arduino Nano Analog Pins

The GPIO pins of the board require 5V to work and the board itself can be powered in three different way: USB Connection, 

Power

: The Arduino Nano has a built-in USB Mini B connection, allowing it to be powered and programmed directly from a computer or laptop. This is a convenient and easy option for many projects, especially when working on a desktop or in a laboratory setting.

Arduino Nano VIN Pin

Arduino Nano 5V Pin

Arduino Nano GND Pin

+3V3

Arduino Nano 3.3V Pin

Regardless of how you choose to power the Arduino Nano, it is important to ensure that you select a power source that is appropriate for your project and that meets the voltage and current requirements of the board and your connected components.

The I/O pins of the board are capable of providing up to 40 mA of current. Any use-cases that requires more current, should be powered by an external power source.

RESET

Arduino Nano Reset Pins

AREF

Arduino Nano AREF Pin

The ATmega328P of the Arduino Nano provides a range of peripherals to utilize in a project. Some of the most important peripherals include:

The ATmega328P has divided I/O pins in three groups (or as it's called in its datasheet: three Ports): Port B, C and D. The pins assigned to each port are:

Each port has three registers for configuring and accessing the I/O pins on that port as well as reading and writing them. 

The processor has two 8-bit timers named Timer/Counter 0 and Timer/Counter 2 as well as a single 16-bit one named Timer/Counter 1. Timers 0 and 2 are general purpose 8-bit Timer/Counter module, with two independent Output Compare Units, and with PWM support. The 16-bit Timer/Counter 1 unit allows accurate program execution timing (event management), wave generation and signal timing measurement.

Arduino Nano Timers are continuously counting from 0 to 255 and go back to 0 (Timer/Counter 1 counts to 65535). The value of a Timer/Counter is available on TCNTx register, where x is the timer number i.e. 0, 1 or 2. 

Each timer is configurable via a set of registers and provides outputs based on the control bits configured on those registers. You can define two threshold value for each timer in OCRxA and OCRxB compare registers so that whenever the timer value reaches any of those values, the processor will do an action based on the current mode of the timer.
The Arduino Nano timer mode can be set by configuring relevant bits in TCCRxA and TCCRxB registers. It can for example be set to call an interrupt routine when the value of the timer (i.e. TCNTx) matches any of the compare registers (e.g. OCRxA or OCRxB). 

Also the Waveform Generator can switch the output level for PWM signals when the value matches the compare registers, so it actually uses this technique to set the duty cycle of the signal. The output of the Waveform Generator for Timer/CounterX is written to OCxA and OCxB registers that are exposed on Aruduino Nano pinout.

Another mode for a timer is to reset the timer whenever its value matches a compare registers.

Here is an example of a code that generates a PWM signal on PIN 

 with 50% duty cycle using Timer/Counter2:

This code is effectively the same as using the 

More fine details about how to configure timers can be find at the processor's datasheet.

Arduino Nano timer pins provide access to the output of these timers as below:

OC0x

OC1x

OC2x

CLKO

ICP1

The watchdog peripheral provides a way to recover from faults in your projects. It can be used to reset the board if it becomes unresponsive or if a critical error occurs. It can also be configured to give an interrupt so that the code can react to such situations. Another option is to set it up to wake-up the Arduino Nano from sleep modes. The timer counts the cycles of a separate on-chip 128kHz oscillator.

The board supports known communication protocols, including USART, I2C, and SPI. These protocols provide a way to interface with a wide range of external components and devices, allowing you to send and receive data, control motors or other devices and more.

MISO

MOSI

USART (Universal Synchronous/Asynchronous Receiver/Transmitter)

Programming the Arduino Nano board is possible via various Integrated Development Environments (IDEs) available. These IDEs provide an easy-to-use interface for users to write, upload, and debug their code. Some of the most popular choices are:

: The official IDE for the Arduino platform, providing a simple and straightforward way to write, upload, and debug code on the board.

: PlatformIO allows developer to compile the same code with different development platforms using only one IDE. It is one of the most popular tools on top of Visual Studio Code. It supports a variety of boards in including Arduino Nano.

: A professional IDE for developing applications on Atmel microcontrollers, including the ATmega328P used on the Arduino Nano.

: The Arduino Web Editor allows you to write code and upload it to Arduino boards from your web browser. It doesn't require user to install any software on his/her computer which makes it a good choice for beginners. Your code will be stored in your Arduino cloud account.

: AVRDUDE is a command-line tool that can be used to program the ATmega328P microcontroller. It supports a wide range of programming methods, including JTAG, ISP, and PDI. It is especially useful for advanced users who are comfortable working with command-line interfaces.

: AVR Studio is a proprietary software that is developed by Atmel, the company that manufactures the microcontroller. It provides advanced features like debugging, programming, and device programming.

Overall he most common approach would be the Arduino IDE or the Arduino Web Editor.

When it comes to getting started with the Arduino Nano or troubleshooting any issues you may encounter, having access to good documentation is essential. Here are a few resources that can be used to get further information about the board:

: The official website of the Arduino platform provides a wealth of information about the Arduino Nano.

: The microcontroller is the heart of the board. This datasheet provides detailed information about the microcontroller's features, including its memory, I/O, and peripherals.

Arduino Nano Pinout: A pinout diagram provides a visual representation of the board's I/O pins and their functions. That's where 

 shines. So no need to go anywhere, just check the diagram at the beginning of this page.

Here are a few features that would be nice to have on the Arduino Nano development board:

Built-in WiFi or Bluetooth connectivity: This would allow for wireless communication and make it easier to connect to other devices or the internet.

Increased memory: The Arduino Nano has limited memory, and an increase in this would allow for more complex projects and programs.

These are just a few examples of the features that could enhance the capabilities of the Arduino Nano development board. It's of course a common shortcoming for many boards on those period (it got released on 2008). Having wireless connectivity was not a common option back then for development boards.

Even though Arduino Nano is one of the most popular boards in the Arduino family, there many development boards with the same form factor or processing power. Here is the list of 3 options to choose from:

: This board has the same form factor of the Arduino Nano. It has ATMega4809 as processor which provides more memory.

Arduino Nano Every

: The Uno board has a similar processing power but comes in a bigger form factor. Some users prefer that for prototyping instead of using Arduino Nano on the breadboard.

: This board is a member of the new generation of Nano family. It has the same form factor as Arduino Nano but provides various sensors and connectivity options. It's a good choice for IoT projects.

Arduino Nano 33 BLE Sense 

There are tons of projects based on Arduino Nano. Here are some of them to inspire you for your next project:

Arduino-Based Universal AC Motor Speed Controller

Arduino Nano Based Hexbug Scarab Robotic Spider

Get comprehensive details on the Arduino Nano development board: Pinout, Powering options, Physical properties, Peripherals & Programming.

The registers of each port are named as (replace the 'x' with the port name):

 - The Data Direction Register for Port x. It's both readable and writable. 

In order to set a pin to input or output you should set the corresponding bit in this register to 1 or 0. For example the following code sets the pin 13 to be an output:

 in Arduino Nano pinout diagram indicates that it belongs to Port B, so the pin direction can be specified via DDRB register. Also the index 5 in 

 indicates that we should set the bit at index 5 to 1 to set pin 

Port Register Pin

 - The Data Register for Port x. It's both readable and writable.

When a pin is set to output, you can set its value to HIGH or LOW by setting the pin's corresponding bit in this register to 1 or 0.

Here is the Arduino Blink example re-written using port register manipulation:

When the pin is set to INPUT, you can read the pin value via PORTx registers.

 - The Pin Value Toggle Register for Port x. It's both readable and writable.

You can toggle a port HIGH or LOW by setting the corresponding pin in this register to 1. Here is another version of the blink example using the PINx register.

The port manipulation technique is very useful when we need to read/write from/to multiple input/output at the same time. An example could be to write parallel to a shift register. Also it has a better performance than typical calls to 

. In cases where even a small performance improvements matters, you may need to consider using this approach.

PB0,PB1,PB2,PB3,PB4,PB5,PC0,PC1,PC2,PC3,PC4,PC5,PC6,PD0,PD1,PD2,PD3,PD4,PD5,PD6,PD7

The ATmega328P processor of the Arduino Nano has an eight channel 10-bit ADC referred as 

 of the board accordingly. The 10-bit ADC provides the resolution of 1024 value which means any analog input signal between 0V to 5V applied to these pins gets mapped proportionately to a value between 0 to 1023.

Analog

ADC0,ADC1,ADC2,ADC3,ADC4,ADC5,ADC6,ADC7

The PWM or variable frequency output generated by the Waveform Generator based on the comparison of the current value of the Timer/Counter 0 with the value in OCR0A/OCR0B registers. 

The OC0A is accessible on Arduino Nano pinout via 

Timer

OC0A,OC0A

The PWM or variable frequency output generated by the Waveform Generator based on the comparison of the current value of the Timer/Counter 1 with the value in OCR1A/OCR1B registers. 

The OC1A is accessible on Arduino Nano pinout via 

OC1A,OC1B

The PWM or variable frequency output generated by the Waveform Generator based on the comparison of the current value of the Timer/Counter 2 with the value in OCR2A/OCR2B registers. 

 is accessible on Arduino Nano pinout via 

OC2A,OC2B

The ATmega328P can output the system clock on the 

O pin. To enable the output, the CKOUT Fuse has to be programmed. This mode is suitable when the chip clock is used to drive other circuits on the system. You can not program fuses using Arduino IDE. So in order to use the 

 output, you need to use another software and program your board using SPI via ICSP headers.

The Timer/Counter 1 incorporates an Input Capture unit that can capture external events and give them a timestamp indicating time of occurrence. The event can be the rising or falling of a signal applied to the 

 pin. Whenever the event happens, the current value of the Timer/Counter 1 is stored in the ICR1 register and the corresponding interrupt routine is called. 

 pin acts as an input. A common use case for this is to measure the signal period. The code in the interrupt routine should copy the value from the ICR1 register to a safe place as soon as possible before it gets overwritten when the next event occurs. This means that it can be used only for low frequency signals.

The following code demonstrates how to print the rising edges of the signal applied to the 

 pin and send it to the computer via Serial interface.

The Timer/Counter 0 can be clocked internally, via the prescaler, or by an external clock source on the 

 pin. When the timer need to be clocked externally, it should be configured via TCCR0B register. The 

 pin is accessible on Arduino Nano pinout via 

The Timer/Counter 1 can be clocked internally, via the prescaler, or by an external clock source on the 

 pin. When the timer need to be clocked externally, it should be configured via TCCR1B register. The 

Arduino Nano has 2 external interrupts. The External Interrupts can be triggered by a falling or rising edge, voltage change or when the voltage level is low. 

You can define a function that would be called whenever the interrupt happens. Such a function is normally called Interrupt Service Routine (ISR). An ISR cannot have any input parameters, and they shouldn’t return any value. In order to tell the process what ISR should be called for each interrupt, the 

 function can be used. It attaches an ISR function to a specific interrupt.

The following example prints a message in the Serial output whenever the voltage level on pin 

 changes (i.e. either from LOW to HIGH or from HIGH to LOW).

 function is used to convert the pin number to its corresponding interrupt number. In this example, the interrupt number on pin 

 is 0. It's recommended to always use this function to find the interrupt number of a pin instead of directly passing the value of 0. Make sure to call the 

 function with a pin number that supports interrupt, otherwise it returns -1, which means the further call to 

Interrupt

INT0,INT1

Arduino Nano Pin Change Interrupt (as their name implies) allows you to run a function when a value of a pin changes. It's another (more limited) interrupt functionality provided by the processor on all the 

 pins on Arduino Nano pinout. The limitation is that unlike external interrupts that can be triggered on rising, falling or change of the voltage level, they only get triggered when the logic level voltage of the corresponding pin changes.

Pin Change Interrupt

Enabling Pin Change Interrupts on Arduino Nano is a three step process:

Enable PCI for the port the given pin belongs to

To learn more about the ports, read the section about the I/O Port Registers.

There is a dedicated pin for each I/O port on PCICR register that should be set to 1 in order to enable PCI on that port. Here is the code that shows how to enable PCI for all the pins on all three ports B, C and D in Arduino Nano.

Next, in order to enable the PCI for a specific pin, we should set the corresponding bit in one of PCMSK0, PCMSK1 or PCMSK2 registers to 1. Each one of these registers handles PCI activation for a specific port as below:

So first we need to figure out the bit index for given pin in Arduino Nano pinout in Pin Register column. For example to enable PCI for pin 

, we know we should set the bit at index 2 of PCMSK0 to 1. The index is counted from the rightmost bit.

The following code demonstrates how to enable the PCI for pin 

The last step is to implement the actual function that should be called when the interrupt happens. You should specify a function named 

  for each port that you want to handle its PCI and it can have one of the following parameters depend on which port it belongs to:

PCINT0_vect for the ISR that handles PCI on port B

PCINT1_vect for the ISR that handles PCI on port C

PCINT2_vect for the ISR that handles PCI on port D

So the function signature will be like this:

Here is a complete example demonstrating how to handle PCI on pin 

 and send a message over Serial communication notifying a change in any of those pins:

 is called for changes on all the pins in the same port, there is no way to tell which pin has changed or what value it has changed to/from. So you should keep the last value of the pins you're monitoring in a variable and then inside the 

 function read the current value of them and compare it with the last one to see if that's the one that has changed or not.

PCINT0,PCINT1,PCINT2,PCINT3,PCINT4,PCINT5,PCINT8,PCINT9,PCINT10,PCINT11,PCINT12,PCINT13,PCINT14,PCINT16,PCINT17,PCINT18,PCINT19,PCINT20,PCINT21,PCINT22,PCINT23

The Analog Comparator compares the input values on the positive pin 

 is higher than the voltage on the negative pin 

, the Analog Comparator output, ACO, is set. The comparator’s output can be set to trigger the Timer/Counter 1 Input Capture function. In addition, the comparator can trigger a separate interrupt, exclusive to the Analog Comparator. The user can select Interrupt triggering on comparator output rise, fall or toggle.

Analog Comparator

In order to use the comparator, you should first decide about the followings:

- What to use as the positive input of the comparator? Possible options are:

The fixed bandgap reference voltage inside the processor

- What to use as the negative input of the comparator? Possible options are:

Any of the analog input pins on the board

- What to do when the comparison result is ready? Possible options are:

Trigger input capture function on Timer/Counter 1

All these answers can be specified by setting different bits on the following dedicated registers:

ADCSRA: ADC Control and Status Register A. By setting the ADEN bit of this register to 0, we can disable the ADC so that the 

ADCSRB: ADC Control and Status Register B. By setting the ACME bit on this register when ADC is switched off, we tell the comparator to use an analog input pin (specified via ADC multiplexer) for the negative input of the comparator.

 pins on the board. It is also possible to select any of the 

Arduino Nano Pinout

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