Mega ADK 2560 ADK User Guide

一、Introduction

The Arduino Mega ADk is also a core circuit board with a USB interface. The biggest difference between it and the Mega2560 is that there is an extra USB main control interface on the Mega ADK for interconnection with the mobile phone of the Andrio system. The processor core of Mega ADK is ATmega2560, which has 54 digital input/output ports (16 of which can be used as PWM output), 16 analog inputs, 4 UART interfaces, a 16MHz crystal oscillator, a USB port, and a power supply socket, an ICSP header and a reset button. Arduino Mega2560 is also compatible with expansion boards designed for Arduino UNO. Arduino Mega2560 has been released to the third edition. Compared with the previous two editions, it has the following new features:

1. Two pins SDA and SCL are added to AREF to support I2C interface; IOREF and a reserved pin are added, and the expansion board will be compatible with 5V and 3.3V core boards in the future.

2. Improved reset circuit design.

3. The USB interface chip is replaced by ATmega16U2 ATmega8U2.

二、Summary

1. Processor ATmega2560

2. Working voltage 5V

3. Input voltage (recommended) 7-12V

4. Input voltage (range) 6-20V

5. Digital IO pin 54 (of which 16 are used as PWM output)

6. Analog input pin 16

7. IO pin DC current 40 mA

8. 3.3V pin DC current 50 mA

9. Flash Memory 256 KB (ATmega328, of which 8 KB is used for bootloader)

10. SRAM 8KB

11. EEPROM 4KB

12. Working clock 16 MHz

三、Power supply

Arduino Mega ADK can be powered in 3 ways, and can automatically select the power supply mode

1. The external DC power supply is powered through the power socket.

2. Connect the battery to the GND and VIN pins of the power connector.

3. The USB interface provides direct power supply.

Power Pin Description

VIN --- When the external DC power supply is connected to the power socket, it can supply power to the outside through VIN; it can also directly supply power to Mega2560 through this pin; when VIN has power, it will ignore the power from USB or other pins.

5V --- Power the 5V chip on the UNO through a voltage regulator or 5V from USB.

3.3V --- 3.3V voltage generated by the voltage regulator, the maximum driving current is 50mA.

GND --- ground pin.

PS: ADK can be used as a USB host controller connected to the mobile phone, so sometimes it is necessary to provide current to the mobile phone. When ADK is powered by USB, the 500mA current provided by USB is for ADK board and mobile phone; when ADK is powered by external DC, the voltage regulator on ADK can provide 1500mA current, of which 750mA is used for ADK board and mobile phone, and the other 750mA will be Assigned to other peripherals connected to ADK.

四、Storage
ATmega2560 includes on-chip 256KB Flash, of which 8KB is used for Bootloader. There are also 8KB SRAM and 4KB EEPROM.

五、Input and output

1. 14 digital input and output ports: the working voltage is 5V, and each channel can output and access a maximum current of 40mA. Each channel is configured with a 20-50K ohm internal pull-up resistor (not connected by default). Besides that, some pins have specific functions

4 serial port signals: serial port 0---0(RX) and 1(TX); serial port 1---19(RX)and 18(TX); serial port 2---17(RX)and 16(TX); Serial ports 3---15(RX) and 14(TX). Among them, the serial port 0 is connected to the internal ATmega8U2 USB-to-TTL chip to provide the serial port receiving signal at the TTL voltage level.

6 external interrupts: 2 (interrupt 0), 3 (interrupt 1), 18 (interrupt 5), 19 (interrupt 4), 20 (interrupt 3), and 21 (interrupt 2). Trigger interrupt pin, which can be set to be triggered by rising edge, falling edge or both.

14 channels of pulse width modulation PWM (0--13): Provide 14 channels of 8-bit PWM output.

SPI (53(SS), 51(MOSI), 50(MISO), 52(SCK)): SPI communication interface.

LED (No. 13): Arduino is specially used to test the reserved interface of LED. When the output is high, the LED is on, otherwise, the LED is off when the output is low.

2. 16 channels of analog input: each channel has a resolution of 10 bits (that is, the input has 1024 different values), the default input signal range is 0 to 5V, and the input upper limit can be adjusted through AREF. In addition, some pins have specific functions

TWI interface (20 (SDA) and 21 (SCL)): support communication interface (compatible with I2C bus).

3. AREF: The reference voltage of the analog input signal.

4. Reset: When the signal is low, the microcontroller chip is reset.

5. USB Host controller MAX3421E: MAX3421E communicates with Arduino through SPI bus, and it will use the following digital interfaces 7(RST), 50(MISO), 51(MOSI), 52(SCK).

PS: Don't use digital 7 port as input or output, because it is used to communicate with MAX3421E in ADK. Non broken out on headers: PJ3 (GP_MAX), PJ6 (INT_MAX), PH7 (SS).

六、Communication interface

1. Serial port: The built-in 4-way UART of ATmega2560 can realize serial port communication with the outside; ATmega16U2 can access serial port 0 to realize the virtual serial port on USB.

2. TWI (I2C compatible) interface:

3. SPI interface:

4. MAX3421E USB main control interface: It can be connected to all devices with USB interface, such as mobile phones, cameras, keyboards and game consoles. 

七、Download program

1. The ATmega2560 on the Arduino Mega ADK has a preset bootloader program, so the program can be directly downloaded to the Mega2560 through the Arduino software.

2. You can directly download the program to ATmega2560 through the ICSP header on Mega2560.

3. The Firmware (firmware) of ATmega16U2 can also be upgraded through the DFU tool.

八、Points to note

1. There is a resettable fuse near the USB port on the Arduino Mega ADK to protect the circuit. When the current exceeds 500mA, the USB connection will be disconnected.

2. Arduino Mega ADK provides an automatic reset design, which can be reset by the host. In this way, the software in the Mega2560 can be automatically reset through the Arduino software, and the reset button is not needed. This function can be enabled and disabled at the silkscreen "RESET EN" on the printed board.

3. The design of Arduino Mega ADK is fully compatible with the design of Arduino USB interface standard version, so the expansion boards used for Arduino UNO and previous series can also be used on Arduino Mega ADK.

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