Description

Arduino Mega 2560

The Arduino Mega 2560 Rev3 with Cable Arduino is a micro-controller board that is based on the CH340 chip. It has a total of 54 digital I/O pins (of which 15 pins can be used for PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16-MHz crystal oscillator, a micro USB connection, a power jack, an ICSP header, and a reset button. It has everything that is required to support the microcontroller’s operation, connect it to a PC with a USB cable or power it up with an AC-DC adapter/battery to get it started. The Arduino Mega is compatible with most shields design for the Arduino Duemilanove or Arduino Diecimila.

The Arduino Mega 2560 is an updated version of Mega. It differs from all previous boards in the manner that it does not use the FTDI USB-to-serial driver chip. Instead, it features the CH340 chip programmed as a USB-to-serial converter.

Version 2 of the Arduino Mega2560 board has a resistor pulling the 8U2 HWB line to ground, making it easier to put it into the DFU mode.

Version 3 of the board has the given new features :

1.0 pinout: An added SDA and SCL pins near the AREF pin and two other new pins are placed near the RESET pin, the IOREF that allows the shields to adapt to the voltage provided from the board. In the future, shields will be compatible with the board that uses the AVR, which operate with 5V and with the Due that operates with 3.3V. The second one is not connected to a pin, which is reserved for future purposes.

Stronger RESET circuit.

Atmega 16U2 replaced with the 8U

Package Includes :

1 x Arduino Mega 2560 Rev3 with Cable Arduino

Specifications and Features of Arduino Mega 2560 Rev3 with Cable Arduino :

1. Microcontroller chip CH340
2. Operating Voltage 5V
3. Input Voltage (recommended) 7-12V
4. Input Voltage (limits) 6-20V
5. Digital Input/Output Pins 54 (15 provide PWM output)
6. Analog Input Pins 16
7. DC per I/O Pin 40 mA
8. DC for 3.3V Pin 50 mA
9. Memory 256 KB of which 8 KB is used in the bootloader
10. S-RAM 8 KB
11. EEP-ROM 4 KB
12. Clock Speed: 16 MHz
13. Dimensions: 111mm x 54mm x 12mm (LxWxH).

About the Arduino Mega 2560 Rev 3 :

The power pin schematics are as given:

V-IN – This represents the input voltage to the 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 – This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 – 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don’t advise it.

3V3 – A 3.3 volt supply is generated by the on-board regulator. The maximum current draw is 50 mA.

GND – Ground pins.

IOREF – This pin on the board provides the voltage reference with which the microcontroller operates. A properly configured shield can read the IOREF pin voltage and select the appropriate power source or enable voltage translators on the outputs for working with the 5V or 3.3V.

The CH340 has 256 KB of memory for storing code (of which 8 KB is used by the bootloader); 8 KB of S-RAM and 4 KB of EEP-ROM (which can be read and written with the EEP-ROM library).

Each of the 54 digital pins on the Mega can be use 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.

Some pins have specialized functions :

Serial : serial0: (RX) and 1 (TX), Serial1: 19 (RX) and 18 (TX), Serial2: 17 (RX) and 16 (TX); Serial3: 15 (RX) and 14 (TX). Used to receive (RX) and transmit (TX) TTL serial data. Pins 0 and 1 are also connect to the corresponding pins of the ATmega16U2 USB-to-TTL Serial chip.

External Interrupts : 2 (interrupt 0), 3 (interrupt 1), 18 (interrupt 5), 19 (interrupt 4), 20 (interrupt 3), and 21 (interrupt 2). 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: 2 to 13 and 44 to 46. Provide 8-bit PWM output with the analogWrite() function.

SPI : 50 (MISO), 51 (MOSI), 52 (SCK), 53 (SS). These pins support SPI communication using the SPI library. The SPI pins are also broken out on the ICSP header; which is physically compatible with the Uno Duemilanove and Diecimila

LED: 13. There is a built-in LED connect to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it’s off.

TWI: 20 (SDA) and 21 (SCL). Support TWI communication using the Wire library. Note that these pins are not in the same location as the TWI pins on the Duemilanove or Diecimila.

The Mega2560 has 16 inputs, each of which provides 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 analogReference() function.

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. They are typically used to add a reset button to shields which block the one on the board.

The Arduino Mega 2560 Rev3 with Cable Arduino has several facilities for communicating with a computer, another, or other microcontrollers. The CH340 provides four hardware UARTs for TTL (5V) serial communication. A CH340 on the board channels one of these over USB and provides a virtual com port to software on the computer (Windows machines will need a .inf file, but OSX and Linux machines will recognize the board as a COM port automatically. The software includes a serial monitor which allows simple textual data to be sent to and from the board. The RX and TX LEDs on the board will flash when data is being transmitted via the CH340 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 Mega2560’s digital pins.

Communication Support :

The CH340 also supports TWI and SPI communication. The software includes a Wire library to simplify the use of the TWI bus; see the documentation for details. For SPI communication, use the SPI library.

The ATmega2560 on the Mega comes pre-burned 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 using ISP or similar; see these instructions for details. The CH340 firmware source code is available in the repository.

TheATmega16U2/8U2 is load with a DFU bootloader, which can be activated by :

On Rev1 boards, the solder jumper is connected on the back of the board (near the map of Italy) and then resetting the 8U2.

On Rev2 or later boards: there is a resistor that pulling the 8U2/16U2 HWB line to ground, making it easier to put into DFU mode. You can then use Atmel’s FLIP software (Windows) or the DFU programmer (Mac OS X and Linux) to load a new firmware. Or you can use the ISP header with an external programmer (overwriting the DFU bootloader). See this user-contributed tutorial for more information.

Rather than requiring a physical press of the reset button before an upload, the Mega 2560 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 ATmega8U2 is connected to the reset line of the ATmega2560 via a 100 nano-farad capacitor. When this line is asserted (taken low), the reset line drops long enough to reset the chip. The software uses this capability to allow you to upload code by simply pressing the upload button in the 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.

Setup Information :

This setup has other implications. When Mega 2560 is connected to either a computer running MacOS 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 Mega 2560. While it is a program 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 open. If a sketch running on the board receives a one-time configuration or other data when it first starts, makes sure that the software with which it communicates waits for a second after opening the connection before sending it.

The Mega2560 contains a trace that can  cut to disable the auto-reset. The pads on either side of the trace can  solder 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; see this forum thread for details.

The Mega 2560 has a re-settable poly-fuse that protects your computer’s USB ports from shorts and over-current. Although most computers provide their internal protection, the fuse provides an extra layer of protection. If more than 500mA apply to the USB port, the fuse will automatically break the connection until the short or overload is remove.

The maximum length and width of the Mega 2560 PCB are 4 and 2.1 inches respectively, with the USB connector and power jack extending beyond the former dimension. Three screw holes allow the board to attach to surface or case. Note that distance between digital pins 7 and 8 is 160 mil (0.16″), not an even multiple of the 100 mil spacing of other pins.

Compatible Devices :

The Mega2560 is design to be compatible with most shields design for the Uno, Diecimila or Duemilanove. Digital pins 0 to 13 (and the adjacent AREF and GND pins); analog inputs 0 to 5, the power header, and ICSP header are all in equivalent locations. Further, the main UART (serial port) is located on the same pins (0 and 1), as are external interrupts 0 and 1 (pins 2 and 3 respectively). SPI is available through the ICSP header on both the Mega2560 and Duemilanove / Diecimila. Please note that I2C is not located on the same pins on the Mega (20 and 21) as the Duemilanove / Diecimila (analog inputs 4 and 5).

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