Arduino Duemilanove
Arduino Duemilanove Board |
Overview
The Arduino Duemilanove ("2009") is a microcontroller board based on the ATmega168 (datasheet) or ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz
crystal oscillator, a USB connection, a power jack, an ICSP header, and
a reset button. It contains everything needed to support the
microcontroller; simply connect it to a computer with a USB cable or
power it with a AC-to-DC adapter or battery to get started.
"Duemilanove" means 2009 in Italian and is
named after the year of its release.
Arduino Duemilanove Lateral View |
Summary
Microcontroller | ATmega168 |
Operating Voltage | 5V |
Input Voltage (recommended) | 7-12V |
Input Voltage (limits) | 6-20V |
Digital I/O Pins | 14 (of which 6 provide PWM output) |
Analog Input Pins | 6 |
DC Current per I/O Pin | 40 mA |
DC Current for 3.3V Pin | 50 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 |
Schematic & Reference Design
EAGLE files: arduino-duemilanove-reference-design.zip
Schematic: arduino-duemilanove-schematic.pdf
Power
The Arduino Duemilanove can be powered via the USB connection or with
an external power supply. The power source is selected automatically.
External (non-USB) power can come either from
an AC-to-DC adapter (wall-wart) or battery. The adapter can be
connected by plugging a 2.1mm center-positive plug into the board's
power jack. Leads from a battery can be inserted in the Gnd and Vin pin
headers of the POWER connector.
The board can operate on an external supply of 6
to 20 volts. If supplied with less than 7V, however, the 5V pin may
supply less than five volts and the board may be unstable. If using
more than 12V, the voltage regulator may overheat and damage the board.
The recommended range is 7 to 12 volts.
The power pins are as follows:
- VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.
- 5V. The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.
- 3V3. A 3.3 volt supply generated by the on-board FTDI chip. Maximum current draw is 50 mA.
- GND. Ground pins.
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 & Output
Each of the 14 digital pins on the Duemilanove 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:
- 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 using the SPI library.
- 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 Duemilanove has 6 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 AREF pin and
the analogReference() function. Additionally, some pins have specialized functionality:
- I2C: analog input pins A4 (SDA) and A5 (SCL). Support I2C (TWI) communication using the Wire library.
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.
See also the mapping between Arduino pins and ATmega168 ports.
Communication
The Arduino Duemilanove 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 Windows version of 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 Duemilanove'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.
Programming
The Arduino Duemilanove can be programmed with the Arduino software (download). Select "Arduino Diecimila or Duemilanove w/ ATmega168" or "Arduino Duemilanove w/ ATmega328" from the Tools > Board menu (according to the microcontroller on your board).
The ATmega168 or ATmega328 on the Arduino Duemilanove 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 Duemilanove 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
Duemilanove 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
Duemilanove. 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.
The Duemilanove contains a trace that can be
cut to disable the auto-reset. The pads on either side of the trace can
be soldered together to re-enable it. It's labeled "RESET-EN". You
may also be able to disable the auto-reset by connecting a 110 ohm
resistor from 5V to the reset line.
USB Over-current Protection
The Arduino Duemilanove has a resettable polyfuse that protects your
computer's USB ports from shorts and overcurrent. Although most
computers provide their own internal protection, the fuse provides an
extra layer of protection. If more than 500 mA is applied to the USB
port, the fuse will automatically break the connection until the short
or overload is removed.
Physical Characteristics
The maximum length and width of the Duemilanove PCB are 2.7 and 2.1
inches respectively, with the USB connector and power jack extending
beyond the former dimension. Three screw holes allow the board to be
attached to a surface or case. Note that the distance between digital
pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil
spacing of the other pins.
Information source : www.arduino.cc