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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system programming is normally accomplished using a Digilent programming cable, either the Digilent JTAG-USB
Programming Cable, or the Digilent JTAG-USB Full Speed Module. The use of an Atmel ISP In System Programmer is
also supported with the use of a suitable flying-lead cable (e.g. Digilent 6 Pin MTE Cable) to convert from the
Digilent 1x6 programming connector convention to the Atmel 2x3 connector convention.
For additional information useful in developing custom firmware for the board, the complete schematic is available
on the Digilent web site.
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Power Supply
The I/O Explorer may be used either as a USB bus powered device or as a self powered device. Jumper JP6 is used
to select between these two options. Install a shorting block in the VUSB position for USB bus power. Install a
shorting block in the VEXT position for self power.
Power switch, SW10, is used to turn board power on or off. Ensure that the power switch is in the ON position to
operate the board.
When operating as a bus powered device, care should be taken in powering devices external to the I/O Explorer.
The 5V USB bus power supply is available at the Pmod ports and other points on the board. Care should be taken
not to exceed the 500mA current limit that USB bus powered devices are allowed to consume. Care should
particularly be taken not to short the USB 5V supply to ground or external voltage supplies as this could result in
damage to the USB hub or PC motherboard to which the I/O Explorer is connected.
When operating as a self powered device, there are three power supply connectors on the I/O Explorer for
connecting the external power supply: J13, J14, and J15. These three connectors are wired in parallel and only one
of the three should be used at a time.
The barrel connector, J13, will normally be used for desktop applications as a self powered device. J13 is the
connector used by the AC supply adapter optionally available from Digilent, or other sources. J13 is a 2.5mm x
5.5mm coaxial connector wired with the center terminal as the positive voltage.
J14 is a screw terminal connector for use with higher current battery packs, bench supplies or other power sources
where use of a hard wired power supply is desirable.
J15 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 J14.
The main operating voltage of the I/O Explorer can be selected between one of two voltages. Jumper JP7 is used to
select between these two voltages. With JP7 in the 3V3 position, the main board power bus is powered from the
output of the 3.3V main power supply regulator on the board. When JP7 is in the 5V0 position, the main power
supply regulator is bypassed, and the main board power bus is powered directly from the applied supply voltage.
When operating as a USB bus powered device, this will be the USB bus 5.0V power supply. When operating as a
self powered device, this will be the voltage of the external supply. In this case, the external supply should not
exceed 5.5V or damage to the board will result.
The main power supply regulator on the I/O Explorer is rated for external power from 3.6 to 9 volts DC. Using a
voltage outside this range could damage the board and connected devices.
The I/O Explorer 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
