Download Features:

Pridgen Vermeer Robotics ATmega128
Revision 0
Features:
6x 8-bit I/O Ports
4x A/D Inputs
6x PWM Headers
2x RS 232 Terminals
Power Bus
LCD Header (4-bit mode)
Smart Power Connecter
Power Switch Header
Power LED
Debug LED
Note: Some pins have multiple uses.
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Pridgen Vermeer Robotics ATmega128
Revision 0
Powering the Board
The Pridgen Vermeer Robotics ATmega128 Board uses a smart power connector to
prevent battery polarity reversal. The power connector uses a 4-pin plug with one outside
pin connected to the positive battery voltage and the opposite inside pin connected to the
negative battery voltage (GND). See Figure 1.
Figure 1
Reversing the power connecter has no adverse effect because the battery voltage will not
be electronically connected to the board. Next to the power connector is the Power
Switch Header. The two pins must be shorted to provide power to the board. Using a
standard jumper will work, but a cable with a SPDT switch is recommended. The cable
and switch must be able to continuously carry 2 amps. When the power is plugged in
correctly, the power LED will turn on.
The ATmega128 Board requires a 6-15V input for the regulators to supply the correct
voltage to the components. All the electronics on the board use VCC = 5V.
Power Bus
A power bus is provided on the ATmega128 Board for powering external devices. VCC is
regulated to 5V. Do not draw more than 500 mA through the power bus.
Figure 2
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Pridgen Vermeer Robotics ATmega128
Revision 0
Programming the Board
The ATmega128 Board uses AVR JTAG programming. Connect the programmer to the
JTAG port on the board and to your computer to establish a connection. The JTAG
header has pin 1 labeled. Please ensure pin 1 on the cable is connected to pin 1 of the
header.
Figure 3
Please ensure you connect the JTAG programmer to the JTAG header, NOT the power
bus.
Figure 4
I/O Ports
The ATmega128 Board has six 8-bit Input/Output ports labeled Port A through Port F
plus a 3-bit Input/Output port labeled G. The I/O ports are located on the sides of the
ATmega128 board. When not used for alternate functions these ports behave as indicated
in the ATmega128 datasheet for general I/O purposes.
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Pridgen Vermeer Robotics ATmega128
Revision 0
I/O Pin Alternate Functions
A/D Converter
Pins F3..0 may be used as Analog inputs for the internal A/D converter of the
ATmega128. Analog signals can be connected directly to pins F3..0 or to the A/D header
which has VCC and GND pins available for powering sensors
Figure 5
JTAG Header
Pins F7..4 are used for JTAG programming and cannot be used for I/O or A/D conversion
inputs. Be careful to ensure the JTAG programmer is connected to the JTAG header and
not the Power Bus header.
RS 232
Pins E0 and E1 may be used as Rx1 and Tx1 respectively; and Pins D2 and D3 may be
used Rx2 and Tx2 respectively. When using serial communication, the DIP switches OE
and /SHDN should be ON. Also, the Rx and Tx switches corresponding to the RS 232
terminals used should be ON. When not using RS 232 communication, turn the switches
OFF.
Figure 6
Figure 7
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Pridgen Vermeer Robotics ATmega128
Revision 0
LCD Connector
All 8 pins of Port C may be used to run the LCD connector. When using the LCD, do
NOT attempt to use Port C for any other function. The LCD connector provides all the
necessary inputs and supply voltages for standard character LCDs. The contrast is
changed using the potentiometer. The connector also supplies and regulates voltage for
the LCD backlight. Please ensure the connected LCD will operate correctly with a 100Ω
resistor as a backlight current limiter as some LCDs will require a different current
limiting resistor.
Figure 8
Debug LED
Pin B0 is connected to the Debug LED on the board. When using B0 for normal I/O
functions, ignore the LED. When using B0 for the debug LED, use active high signals
(i.e. write a 1 to turn on the LED and a 0 to turn off the LED).
Figure 9
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Pridgen Vermeer Robotics ATmega128
Revision 0
PWM/Servo Header
Pins E5..3 and B7..5 may be used for PWM generation. When using one of the pins for
PWM, do not use it for general I/O. The Servo Header is internally connected to Pins
E5..3 and B7..5 as shown in Table 1.
Figure 10
Servo Header
AtMega128
1
E5
2
E4
3
E3
Table 1
4
B7
5
B6
6
B5
Refer to the ATmega128 datasheet for PWM generation.
Table 2 shows all the alternate functions for pins on the Pridgen Vermeer Robotics
AtMega128 Board. When using the alternate function, do NOT use the pin for general
I/O.
Pin
Alternate
Function
B0
Debug LED
B5
Servo 6
B6
Servo 5
B7
Servo 4
C7..0 LCD Connector
E3
Servo 3
E4
Servo 2
E5
Servo 1
F0
A/D 0
F1
A/D 1
F2
A/D 2
F3
A/D 3
Table 2
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