Digilent Cerebot II Manuel de référence - Page 3

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Cerebot II Reference Manual

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

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

select jumper associated with the Pmod

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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

Digilent, Inc.

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