Atmel AVR364 User manual

AVR364: MEGA-1284P Xplained Hardware
User's Guide
Features
• Atmel®megaAVR®ATmega1284P microcontroller
- Target controller
• Atmel AVR®AT32UC3B1256 32-bit microcontroller
- Board controller
- Communication gateway
• Analog input (to ADC)
- Temperature sensor
- Light sensor
- RC filter
• Digital I/O
- Three mechanical buttons
- Four LEDs
- Four expansion headers
• Footprints for external memory
- Atmel AT45DB series DataFlash® serial flash
- Atmel AT25DF series industrial standard serial data flash
• Touch
- One Atmel QTouch®button
1 Introduction
The Atmel MEGA-1284P Xplained evaluation kit is a hardware platform for
evaluating the ATmega1284P MCU.
The kit offers a large range of features that enable the megaAVR user to get
started using megaAVR peripherals right away and to get an understanding of how
to integrate a megaAVR MCU in their own design.
Figure 1-1. MEGA-1284P Xplained evaluation kit.
8-bit Atmel
Microcontrollers
Application Note
Rev. 8377B-AVR-11/11

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2 Related items
Atmel AVR Studio®4 (free IDE from Atmel)
http://atmel.com/dyn/products/tools_card.asp?tool_id=2725&category_id=163&family
_id=607&subfamily_id=760
Atmel AVR Dragon™ (on-chip programming and debugging tool)
http://atmel.com/dyn/products/tools_card.asp?tool_id=3891&category_id=163&family
_id=607&subfamily_id=760
Atmel AVR JTAGICE mkII (on-chip programming and debugging tool)
http://atmel.com/dyn/products/tools_card.asp?tool_id=3353&category_id=163&family
_id=607&subfamily_id=760
Atmel AVR ONE! (on-chip programming and debugging tool)
http://atmel.com/dyn/products/tools_card.asp?tool_id=4279&category_id=163&family
_id=607&subfamily_id=760

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3 General information
This document targets the Atmel ATmega1284P evaluation kit revision 3, and parts of
the document may, therefore, be inconsistent with earlier revisions of the product. For
earlier revisions, please refer to the schematics, which is the only documentation
available for these revisions. The Atmel MEGA-1284P Xplained kit is intended to
demonstrate the ATmega1284P, and the hardware that relates to the Atmel
AT32UC3B1256 (board controller) is, therefore, not covered in detail in this
document.
Figure 3-1. Overview of the MEGA-1284P Xplained kit.

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Figure 3-2. Functional overview of the Atmel MEGA-1284P Xplained kit.
3.1 Preprogrammed firmware
The MEGA-1284P Xplained kit comes with both the Atmel ATmega1284P and the
Atmel AT32UC3B1256 preprogrammed.
The preprogrammed firmware in the ATmega1284P is set up with example code that
allows the user to choose different sleep modes, and provides an example of how to
use the light sensor to dim the four onboard LEDs. It also includes a boot loader
(AVROSP) which allows the user to reprogram the ATmega1284P without using an
external programmer. Please refer to the Atmel application note, AVR370: MEGA-
1284P Xplained Getting Started Guide, for more details regarding the
preprogrammed firmware.
The preprogrammed AT32UC3B1256 firmware offers features such as a boot loader
for self-programming of the board controller itself, and a USART-to-USB gateway,
which can be used to communicate with the target controller, the ATmega1284P.

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3.2 Power supply
The kit is powered via the USB connector, which presents two options for powering it:
Either connect the kit to a PC through a USB cable or to a 5V USB power supply
(AC/DC adapter).
The 5V is regulated to 3.3V with an LDO regulator, which provides power to the entire
board. The Atmel ATmega1284P is powered by 3.3V, but if 1.8V operation is desired,
some modifications to the board are needed. This includes replacing the regulator
with one that delivers a 1.8V output and rerouting the power to the device (see
schematic for an explanation). As some of the other ICs on the Atmel MEGA-1284P
Xplained require 3.3V to operate correctly, these devices have to be removed.
3.3 Measuring the ATmega1284P power consumption
As part of an ATmega1284Pevaluation, it can be of interest to measure its power
consumption. The two-pin power measurement header is the only connection
between the VCC_P3V3 common power plane and the VCC_MCU_P3V3 power
plane. By replacing the jumper with an ammeter, it is possible to determine the
ATmega1284P current consumption. To locate the power measurement header,
please refer to Figure 3-1.
Do not power the board without having the jumper or an ammeter mounted. If
this is done the board might be powered through an I/O pin. The result might be
erratic behavior and the device might get damaged.
3.4 Communication through the USART-to-USB gateway
The ATmega1284P USART is connected to a USART on the Atmel AT32UC3B1256.
The ATmega1284P USART is communicating at 57600 baud using one start bit, eight
data bits, one stop bit, and no parity.
When the AT32UC3B1256 device is enumerated (connected to a PC). the data
transmitted from the ATmega1284P is passed to a (virtual) COM port. This means
that it is possible to use a terminal program on a PC to receive the transmitted data.
Similarly data transmitted from the PC COM port is passed to the ATmega1284P
USART through the gateway.

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4 Connectors
The Atmel MEGA-1284P Xplained kit has five 10-pin, 100mil headers. Two headers
have a fixed communication interface (J1 and J4). One header has analog
functionality (J2), and the last header (J3) has general purpose digital I/O.
The 90° angled header is the Atmel ATmega1284P JTAG programming and
debugging header.
For the location of the respective headers, refer to Figure 3-1.
4.1 Programming headers
The ATmega1284P can be programmed and debugged by connecting an external
programming/debugging tool to the JTAG pin header. The pin header has a standard
JTAG programmer pin-out (refer to online help in the Atmel AVR Studio), enabling
tools like the Atmel AVR JTAGICE mkII or the Atmel AVR ONE! to be connected
directly to the header.
The grey, female, 10-pin header on the AVR JTAGICE mkII must be used when
connecting to the kit. A scoring in the board is made to fit the orientation tab on
the header.
A standoff adapter (nr. 1) is needed when using the AVR ONE!
Pin 1 on the JTAG header is at the top right corner. This is rotated 180°
compared to the other headers (J1, J2, J3, and J4).
Table 4-1. MEGA-1284P Xplained programming and debugging interface – JTAG.
Pin JTAG
(1)
1 TCK
2 GND
3 TDO
4 VCC
5 TMS
6 nSRST
7 -
8 -
9 TDI
10 GND
Note: 1. Standard pin-out for the AVR JTAGICE mkII and other Atmel programming tools
The Atmel AT32UC3B1256 can be programmed through its boot loader. The boot
loader is evoked by shorting the two holes marked BOOTLOADER BOARD
CONTROLLER on the bottom side of the board before applying power to the board.
The two holes have 100mil spacing, enabling the user to solder in a two-pin header
and use a jumper to easily enter the boot loader. Programming is performed through
the boot loader programmer target in the Atmel AVR Studio.
Alternatively, the AT32UC3B1256 can also be programmed by connecting a
programming tool, such as the AVR JTAGICE mkII, to the 10 holes marked JTAG
BOARD CONTROLLER on the bottom side of the board. The holes have 100mil
spacing, letting the user solder in a 10-pin header to program the board controller.

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Please note that programming the Atmel AT32UC3B1256 using a programming
tool will erase the boot loader.
Please refer to the Atmel application note, AVR370: MEGA-1284P Xplained
Getting Started Guide, for more details regarding how to program the onboard
microcontrollers.
4.2 I/O expansion headers
There are four available I/O expansion headers in the kit. Because of the low pin
count on the device, the I/O expansion header pins are shared with onboard
functionality. If “clean” expansion ports are needed, cut-straps are available to
remove onboard functionality. Table 4-2 through Table 4-5 show what is shared on
the respective header pins.
Table 4-2. Atmel MEGA-1284P Xplained I/O expansion header – J1.
Pin J1 ATmega1284P pin Shared with onboard functionality
1 TWI SDA PC1 Header J4, board controller
2 TWI SCL PC0 Header J4, board controller
3 USART RXD0 PD0 Header J4
4 USART TXD0 PD1 Header J4
5 SPI SS
(1) PB4 Board controller
6 SPI MOSI
(1) PB5 Header J4, DataFlash, board controller
7 SPI MISO
(1) PB6 Header J4, DataFlash, board controller
8 SPI SCK
(1) PB7 Header J4, DataFlash, board controller
9 GND - -
10 VCC_P3V3 - -
Note: 1. These signals can be disconnected from the board controller by cutting the cut-
straps marked SPI on the bottom side of the board.
Table 4-3. MEGA-1284P Xplained I/O expansion header – J2.
Pin J2 ATmega1284P pin Shared with onboard functionality
1 ADC0
(1) PA0 Possible to connect to AREF
2 ADC1 PA1 -
3 ADC2 PA2 -
4 ADC3 PA3 -
5 ADC4 PA4 -
6 ADC5
(2) PA5 Filter output
7 ADC6
(2) PA6 Light sensor
8 ADC7
(2) PA7 NTC sensor
9 GND - -
10 VCC_ANA_P3V3 - -
Notes: 1. AREF with 100nF capacitor to GND can be connected to ADC0 by shorting two
pads marked EXTERNAL AREF on the bottom side of the board.
2. These signals can be disconnected from the sensor/filter output by cutting the
cut-straps marked SENSORS & FILTER on the bottom side of the board.

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Table 4-4. Atmel MEGA-1284P Xplained I/O expansion header – J3.
Pin J3 ATmega1284P pin Shared with onboard functionality
1 GPIO0 PB0 SW0, LED0
2 GPIO1 PB1 SW1, LED2
3 GPIO2 PB2 SW2, LED3
4 GPIO3 PB3 LED1
5 GPIO4 PD4 J4 (SPI SS1), DataFlash (SPI SS1)
6 GPIO5
(1) PD5 Filter input
7 GPIO6 PC4 JTAG(TDO)
8 GPIO7 PC5 JTAG(TDI)
9 GND - -
10 VCC_P5V0
(2) - -
Notes: 1. This signal can be disconnected from the filter input by cutting the cut-strap
marked FILTER INPUT in the SENSORS & FILTER section on the bottom side
of the board.
2. Pin 10 of header J3 is connected to the USB voltage (VCC_P5V0).
Table 4-5. MEGA-1284P Xplained I/O expansion header – J4.
Pin J4 ATmega1284P pin Shared with onboard functionality
1 TWI SDA PC1 Header J1, board controller
2 TWI SCL PC0 Header J1, board controller
3 USART RXD1 PD2 Board controller
4 USART TXD1 PD3 Board controller
5 SPI SS1 PD4 Header J3 (GPIO4), DataFlash
6 SPI MOSI
(1) PB5 Header J1, DataFlash, board controller
7 SPI MISO
(1) PB6 Header J1, DataFlash, board controller
8 SPI SCK
(1) PB7 Header J1, DataFlash, board controller
9 GND - -
10 VCC_P3V3 - -
Note: 1. These signals can be disconnected from the board controller by cutting the cut-
straps marked SPI on the bottom side of the board.

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5 Memories
The Atmel MEGA-1284P Xplained kit does not have any external memories mounted
on the board. Footprints are available for adding either an industrial standard flash
device or an Atmel proprietary serial DataFlash device.
The footprints share the same SPI lines, including the chip select, and it is,
therefore, not possible to mount devices on both footprints at the same time.
Table 5-1. Compatible devices for the footprints.
Atmel AT45DB Atmel AT25DF
AT45DB64D2-CNU AT25DF641A-SH
AT45DB321D-MWU AT25DF321A-SH
AT45DB161D-SS AT25DF161-SH
AT45DB081D-SS AT25DF081-SSH
AT45DB041D-SS AT25DF021-SSH
AT45DB021D-SS
AT45DB011D-SS

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6 Miscellaneous I/O
6.1 Mechanical buttons
The board is equipped with three mechanical buttons. The buttons (SW0:2) are
shared with LED0, LED2, and LED3. Onboard protection circuitry is added to avoid a
short when driving the port high at the same time as pushing the button, which will
short it to the ground. To be able to use both button and LED, time multiplexing has to
be used.
To be able to detect a button press, the firmware has to periodically set the I/O pin to
input with pull-up and check if it is low. When doing this fast enough, the human eye
will not see any change in the LED.
6.2 LEDs
The Atmel MEGA-1284P Xplained has four standard yellow LEDs mounted onboard,
which are connected to the Atmel ATmega1284P. The four LEDs are active low.
LED0, LED2, and LED3 are shared with the three mechanical buttons (SW0:2). When
turning an LED on, set the I/O pin to output low. When turning an LED off, set the I/O
pin as input with pull-up. The protection circuitry added to the button will make the
LED shine brighter when the button is pressed and the LED is turned on. When the
LED is off, any button press will light up the LED.
The Atmel MEGA-1284P Xplained also has one dual LED mounted near the USB
connector. This is the power and status LED, which is connected to the board
controller. This LED will be green when power is applied, and will toggle between
green and orange when communication over USB is ongoing.
6.3 Analog I/O
An RC filter, a light sensor, and an NTC are connected to ADC5, ADC6, and ADC7,
respectively. These analog sources can be used as input to the ADC. All of the
analog signals can be disconnected by cutting the cut-straps on the bottom side of
the board.
The RC filter (first-order low-pass) has an approximate 3dB cut-off frequency of
159Hz. The input to the RC filter is GPIO5 (PD5) on the ATmega1284P, which can be
configured to output a PWM signal to the RC filter. This can be used to generate a
DC voltage on the output of the RC filter, which can be measured on the ADC5 pin.
As this is a first-order filter, the ripple on the DC voltage is inversely proportional to
the input frequency. A higher input frequency will result in lower ripple on the output.
6.4 Touch
The MEGA-1284P XPLAINED kit has one Atmel QTouch button, QTB0.
Table 6-1. MEGA-1284P Xplained touch connections.
Touch sensor onboard
reference QTouch method pin name ATmega1284P pin
QTB0 SNSK0 PD7
QTB0 SNS0 PD6