I/O Explorer™ USB Reference Manual
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
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J7-J9
Ground Posts
These provide a GND connection for use when using external test equipment, such as an
oscilloscope, to probe signals on the board.
J10
Servo Bus Power
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.
J11
Internal I2C Bus
This connector provides access to the two signals for the internal I2C bus used to communicate
between the two microcontrollers and the MCP4728 DAC.
J12
TWI BUS Daisy Chain Connector
This connector is used to connect external devices to the DTWI bus.
J13-J15
External Power Supply Connectors
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.
JP1
Primary Microcontroller (AT90USB646) In-System-Programming Connector
This connector is used to access the primary microcontroller for in-system-programming. It is
intended for use with a Digilent programming cable, although other Atmel AVR in-system
programmers will work with a suitable cable adapter.
JP2
Secondary Microcontroller (ATmega165P) In-System-Programming Connector
This connector is used to access the secondary microcontroller for in-system-programming. It is
intended for use with a Digilent programming cable, although other Atmel AVR in-system
programmers will work with a suitable cable adapter.
JP3
Servo Bus Power Select
Insert a shorting block on this jumper to join the servo power bus, VS, to the main board power
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.
JP4 & JP5
TWI Bus Pull-up Enable
These jumpers are used to enable/disable the pull-ups on the DTWI bus. Installing the shorting
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.
JP6
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
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.
J7
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.
