Digilent I/O Explorer Reference Manual - Page 16

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I/O Explorer™ USB Reference Manual

Ground Posts

J7-J9

These provide a GND connection for use when using external test equipment, such as an

oscilloscope, to probe signals on the board.

Servo Bus Power

J10

This screw terminal connector is used to provide power to the servo power bus VS when the servo

power bus is being powered separately from the board main power bus.

Internal I2C Bus

J11

This connector provides access to the two signals for the internal I2C bus used to communicate

between the two microcontrollers and the MCP4728 DAC.

TWI BUS Daisy Chain Connector

J12

This connector is used to connect external devices to the DTWI bus.

External Power Supply Connectors

J13-J15

These three connectors are wired in parallel and are used to connect an external power source to

the board when operating the I/O Explorer as a self-powered USB device, or when not using USB.

Primary Microcontroller (AT90USB646) In-System-Programming Connector

This connector is used to access the primary microcontroller for in-system-programming. It is

JP1

intended for use with a Digilent programming cable, although other Atmel AVR in-system

programmers will work with a suitable cable adapter.

Secondary Microcontroller (ATmega165P) In-System-Programming Connector

This connector is used to access the secondary microcontroller for in-system-programming. It is

JP2

intended for use with a Digilent programming cable, although other Atmel AVR in-system

programmers will work with a suitable cable adapter.

Servo Bus Power Select

Insert a shorting block on this jumper to join the servo power bus, VS, to the main board power

JP3

bus, VU. With the shorting block installed, the VS bus is powered from the main board power

supply. With the shorting block removed, the VS bus is powered via connector J10.

TWI Bus Pull-up Enable

These jumpers are used to enable/disable the pull-ups on the DTWI bus. Installing the shorting

JP4 & JP5

blocks enables the pull-ups, removing the shorting blocks disables them.

The pull-ups on the I/O Explorer are implemented using current mirrors, rather than simple pull-

up resistors. This provides improved reliability when driving longer busses.

Main Power Source Select

This jumper is used to select the main power source for the board. Place a shorting block in the

VUSB position to power the board from the USB connector. Place a shorting block in the VEXT

JP6

position to power the board from one of the external power connectors J13, J14, or J15. An

external power supply should provide a regulated 5V. An external voltage greater than 5.5V

should never be applied or damage to the board will occur.

Operating Voltage Select

This jumper is used to select the operating voltage for the board. Place a shorting block in the 3V3

position to operate the board from the internal 3.3V regulator. Place a shorting block in the 5V0

position to operate the board from the input supply (either USB or externally applied 5V) voltage.

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