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Arduino Nano, Front End |
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Arduino Nano, Back End |
Overview:
The Arduino Nano is a small, complete, and breadboard-friendly board based on the ATmega328 (Arduino Nano 3.0) or ATmega168
(Arduino Nano 2.x). It has more or less the same functionality of the
Arduino Duemilanove, but in a different package. It lacks only a DC
power jack, and works with a Mini-B USB cable instead of a standard one.
The Nano was designed and is being produced by Gravitech.
Schematic and Design
Arduino Nano 2.3 (
ATmega168):
manual (pdf),
Eagle files.
Note:
since the free version of Eagle does not handle more than 2 layers, and
this version of the Nano is 4 layers, it is published here unrouted, so
users can open and use it in the free version of Eagle.
Specifications:
Microcontroller | Atmel ATmega168 or ATmega328 |
Operating Voltage (logic level) | 5 V |
Input Voltage (recommended) | 7-12 V |
Input Voltage (limits) | 6-20 V |
Digital I/O Pins | 14 (of which 6 provide PWM output) |
Analog Input Pins | 8 |
DC Current per I/O Pin | 40 mA |
Flash Memory | 16 KB (ATmega168) or 32 KB (ATmega328) of which 2 KB used by bootloader |
SRAM | 1 KB (ATmega168) or 2 KB (ATmega328) |
EEPROM | 512 bytes (ATmega168) or 1 KB (ATmega328) |
Clock Speed | 16 MHz |
Dimensions | 0.73" x 1.70" |
Power:
The Arduino Nano can be powered via the Mini-B USB connection, 6-20V
unregulated external power supply (pin 30), or 5V regulated external
power supply (pin 27). The power source is automatically selected to the
highest voltage source.
The FTDI FT232RL
chip on the Nano is only powered if the board is being powered over USB.
As a result, when running on external (non-USB) power, the 3.3V output
(which is supplied by the FTDI chip) is not available and the RX and TX
LEDs will flicker if digital pins 0 or 1 are high.
Memory
The ATmega168 has 16 KB of flash memory for storing code (of which 2 KB is used for the bootloader); the ATmega328 has 32 KB, (also with 2 KB used for the bootloader). The ATmega168 has 1 KB of SRAM and 512 bytes of EEPROM (which can be read and written with the EEPROM library); the ATmega328 has 2 KB of SRAM and 1 KB of EEPROM.
Input and Output
Each of the 14 digital pins on the Nano can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead()
functions. They operate at 5 volts. Each pin can provide or receive a
maximum of 40 mA and has an internal pull-up resistor (disconnected by
default) of 20-50 kOhms. In addition, some pins have specialized
functions:
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Arduino Nano, Front End With Labels |
- Serial: 0 (RX) and 1 (TX).
Used to receive (RX) and transmit (TX) TTL serial data. These pins
are connected to the corresponding pins of the FTDI USB-to-TTL Serial
chip.
- External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details.
- PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the analogWrite() function.
- SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK).
These pins support SPI communication, which, although provided by the
underlying hardware, is not currently included in the Arduino language.
- LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off.
The Nano has 8 analog inputs, each of
which provide 10 bits of resolution (i.e. 1024 different values). By
default they measure from ground to 5 volts, though is it possible to
change the upper end of their range using the analogReference() function. Additionally, some pins have specialized functionality:
- I2C: 4 (SDA) and 5 (SCL). Support I2C (TWI) communication using the Wire library (documentation on the Wiring website).
There are a couple of other pins on the board:
- AREF. Reference voltage for the analog inputs. Used with analogReference().
- Reset. Bring this line
LOW to reset the microcontroller. Typically used to add a reset button
to shields which block the one on the board.
Communication
The Arduino Nano has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The
ATmega168 and
ATmega328 provide UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An FTDI
FT232RL on the board channels this serial communication over USB and the
FTDI drivers
(included with the Arduino software) provide a virtual com port to
software on the computer. The Arduino software includes a serial
monitor which allows simple textual data to be sent to and from the
Arduino board. The RX and TX
LEDs on the
board will flash when data is being transmitted via the FTDI chip and
USB connection to the computer (but not for serial communication on pins
0 and 1).
A SoftwareSerial library allows for serial communication on any of the Nano's digital pins.
The ATmega168 and ATmega328 also support I2C (TWI) and SPI communication. The Arduino software includes a Wire library to simplify use of the I2C bus. To use the SPI communication, please see the ATmega168 or ATmega328 datasheet.
Programming
The Arduino Nano can be programmed with the Arduino software (
download). Select "Arduino Diecimila, Duemilanove, or Nano w/
ATmega168" or "Arduino Duemilanove or Nano w/
ATmega328" from the
Tools > Board menu (according to the microcontroller on your board).
The
ATmega168 or
ATmega328 on the Arduino Nano comes preburned with a bootloader
that allows you to upload new code to it without the use of an external
hardware programmer. It communicates using the original
STK500 protocol (
reference,
C header files).
You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit Serial Programming) header.
Automatic (Software) Reset
Rather then requiring a physical press of the reset button before an
upload, the Arduino Nano is designed in a way that allows it to be reset
by software running on a connected computer. One of the hardware flow
control lines (DTR) of the FT232RL is connected to the reset line of the ATmega168 or ATmega328
via a 100 nanofarad capacitor. When this line is asserted (taken low),
the reset line drops long enough to reset the chip. The Arduino
software uses this capability to allow you to upload code by simply
pressing the upload button in the Arduino environment. This means that
the bootloader can have a shorter timeout, as the lowering of DTR can be
well-coordinated with the start of the upload.
This setup has other implications. When the
Nano is connected to either a computer running Mac OS X or Linux, it
resets each time a connection is made to it from software (via USB).
For the following half-second or so, the bootloader is running on the
Nano. While it is programmed to ignore malformed data (i.e. anything
besides an upload of new code), it will intercept the first few bytes of
data sent to the board after a connection is opened. If a sketch
running on the board receives one-time configuration or other data when
it first starts, make sure that the software with which it communicates
waits a second after opening the connection and before sending this
data.
Major Information source : arduino.cc
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