Digilent Cerebot II Board User Manual

CCeerreebboott IIII™

Cerebot II Circuit Diagram

RReeffeerreennccee MMaannuuaal

™ BBooaarrdd

l

Revision: February 9, 2009
Note: This document applies to REV B of the board.

Overview

The Cerebot II board is a useful tool for
embedded control and robotics projects for
both students and hobbyists.

Its versatile design and programmable
microcontroller lets you access numerous
peripheral devices and program the board for
multiple uses. The board has many I/O
connectors and power supply options and
supports a number of programming options
including the free Atmel AVR® Studio 4, and
WinAVR.

The Cerebot II has a number of connections
for peripheral devices. It provides eight
connectors for attaching Digilent Pmod™
peripheral modules. Digilent peripheral
modules include H-bridges, analog-to-digital
and digital-to-analog converters, speaker
amplifier, switches, buttons, LEDs, as well as
converters for easy connection to RS232,
screw terminals, BNC jacks, servo motors, and
more.

Features include:

• an ATmega64L microcontroller

• eight hobby RC servo connectors

• eight Pmod connectors for Digilent

peripheral module boards

• an on-board voltage regulator

• multiple flexible power supply jumper

options

• support for the Digilent JTAG-3 Parallel
and JTAG-USB programming cables

• support for the Atmel AVRISP in­system programmer

• support for the Atmel AVR JTAGICE
mkII debugging tool

• ESD protection and short circuit
protection for all I/O pins.

Various po wer

conn ectors

3.3V

regu lator

64K Flash

(Inte rnal)

2K E EPRO M

(Inte rnal)

4K S RAM

(Inte rnal)

8

JA

Mem

Mem

Adr/

Data

www.di g i l e n t i n c . com

215 E Main Suite D | Pullman, WA 99163

User Input

Jumper

VCC

[phone] Voice and Fax

4 LE Ds

GND

8MH z

crys tal

Reset
button

Atmel

ICE port

Inter nal

Oscillator

Atmel

ISP port

ATmega64L

TQ6 4

8 8 8 4 4 4 8

JB

JC

JD

Adr

Mem

SPI

Ctl

UAR T

TWI

UAR T

Eight Pmod conne ctors

JE

H-bri dgeJFH-br idge

LED s

JG

H-bri dge

&

UART, SPI,
&TW I port s

8

JH

Anal og

&

JTA G

®

Digil ent

ISP port

Eigh t servo
conn ectors

Doc: 502-128 page 1 of 10

Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.

Cerebot II Reference Manual Digilent, Inc.

Features of the ATmega64L include:

• a serial peripheral interface (SPI)

• two USART serial interfaces

• Atmel TWI serial interface

• eight 10-bit analog inputs

• two 8-bit timer counters

• two 16-bit timer counters

• 64KB program flash

• 2KB user EEPROM

• 4KB internal RAM

• an analog comparator.

For more information on the ATmega64L
microcontroller, refer to the data sheet
available at www.atmel.com.

Functional Description

The Cerebot II is designed for embedded
control and robotic applications as well as
microprocessor experimentation. Firmware
suitable for many applications can be
downloaded to the Cerebot II’s programmable
ATmega64L microcontroller.

The board has a number of connection
options, and is specially designed to work with
the Digilent line of Pmod peripheral modules
with various input and output functions. For
more information, see www.digilentinc.com.

The Cerebot II has two programming interface
options: The Digilent in-system-programming
option is accessed via connector J1. A Digilent
USB or parallel programming cable can be
attached to connector J1. The Digilent AVR
Programmer application, available from the
Digilent Web site, can be used to program the
board via the Digilent programming cable.
Alternatively, the Atmel AVRISP in-system
programmer can be used. The AVRISP is
connected to connector J2 and programming is
done using the Atmel in-system-programming
application built into the Atmel AVR Studio
software. The Cerebot II also provides the
ability to use the Atmel AVR JTAGICE mkII
debugging tool for programming the board and
debugging the user firmware.

www.digilentinc.com page 2 of 10

Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.

The Cerebot II features a flexible power supply
routing system with a number of options for
powering the Cerebot II as well as peripheral
modules connected to the board.

Pmod Connectors

The Cerebot II has eight Pmod connectors for
connecting to Digilent Pmod peripheral
modules. There are two styles of Pmod
connector. The original Pmod connector
standard uses a six-pin-header style of
connectors providing four I/O signals, ground
and a switchable power connection. The power
connection is switchable between the
regulated 3.3V main board supply and the
unregulated input supply.

The newer Pmod connector standard uses a
12-pin (2x6) header connector and provides
eight signal pins, two grounds, and two
switchable power connections. The pin
arrangement is such that the new connector is
equivalent to two of the older connectors.

Digilent Pmod peripheral modules can either
be plugged directly into the connectors on the
Cerebot II or attached via cables. Digilent has
a variety of Pmod interconnect cables
available.

See the “Pmod Headers and SPI Connection”
section below for more information about
connecting peripheral modules and other
devices to the Cerebot II. It lists the header
connectors with their designed base function
and a mapping to the Atmega64L I/O register
ports. All pins can be used as general-purpose
digital I/O ports.

Power Supply Connectors

The Cerebot II may be powered via dedicated
power supply connectors, or it can be powered
through any of the board’s Pmod connectors.
The Cerebot II can also be powered through
the servo power connector.

The Cerebot II is rated for external power from

3.6 to 9 volts DC. Using voltage outside this

Cerebot II Reference Manual Digilent, Inc.

range could damage the Cerebot II and
connected devices.

There are three different power supply
connectors on Cerebot II for board/processor
power: J7, J8, and J9.

The barrel connector, J7, is useful for desktop
development and testing where use of
batteries is cost- or time-prohibitive. J7 is the
connector used by the AC supply adapter
available from Digilent. J7 is a 2.5mm x 5.5mm
coaxial connector wired with the center
terminal as the positive voltage.

J8 is a two-pin male header that provides easy
battery or battery-pack connection. Digilent has
both two-cell and four-cell AA battery holders
with two pin connectors available for
connection to J8.

J9 is a screw terminal connector for an
alternative power supply connection.

Connectors J7, J8, and J9 are wired in parallel
and connect to one terminal of the power
switch, SW1. The other terminal of SW1
connects to the main unregulated power bus
VU. The VU power bus connects to the center
terminal of the voltage regulator input jumper
JP1 and also connects to the VU terminal of
the power select jumper associated with each
Pmod connector.

Jumper JP1 is used to select the voltage for
the main board power bus VCC. When JP1 is
in the ‘normal’ position, the VCC power bus is
powered by the output of the on-board 3.3V
regulator. When JP1 is in the ‘bypass’ position,
the on-board voltage regulator is bypassed and
the VCC bus is connected directly to the VU
bus. In this case, the microcontroller and other
on-board electronics are powered directly from
the voltage supply connected to VU. In this
case, the input voltage must be in the range

2.7V – 5.5V. A supply voltage outside this
range can permanently damage the board.

You can also power the Cerebot II from any
Pmod header connector. Place the power

connector in the VU position to supply power to
the VU bus, or the VCC position to supply
power to the VCC bus. If power is being
supplied to the VU bus, JP1 should be in the
‘normal’ position so that the on-board regulator
will be able to regulate the supplied voltage to
the 3.3V board operating voltage. If the Pmod
connector power routing jumper is in the VCC
position, the shorting block on JP1 should be
placed in the ‘bypass’ position or removed.

The Cerebot II has a second screw terminal
connector, J10 that supplies power to the
servo power bus, VS, to power the RC hobby
servo connectors. This allows servos to be
powered from a separate power supply than
the one powering the electronics on the
Cerebot II. This can be useful when using
servos that draw large amounts of power.

Jumper JP2 can be used to connect the
Cerebot II unregulated power bus VU to the
servo power bus, VS. When no shorting block
is installed on JP2, the VU and VS busses are
separate. When a shorting block is on JP2, the
two busses are joined and the VU bus can be
powered in any of the previously indicated
ways, or from connector J10.

The Cerebot II can provide power to any
peripheral modules attached to the Pmod
connectors and to TWI devices powered from
the TWI power daisy chain connectors, J4 and
J5. Each Pmod connector provides power pins
that can be powered by either unregulated
voltage, VU, or regulated voltage, VCC, by
setting the voltage jumper block to the desired
position. The TWI power connectors only
provide regulated voltage, VCC.

The regulated voltage on the VCC bus is
provided by an on-board voltage regulator.
This regulator is capable of providing a
maximum of 500mA of current. The
ATmega64L microcontroller will use
approximately 15mA when running at 8MHz.
The remaining current is available to provide
power to attached Pmod and TWI devices. The
regulator is on the bottom of the board, near
the power connectors, and will get warm when

select jumper associated with the Pmod

www.digilentinc.com page 3 of 10

Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.