Digilent chipKIT Motor Shield Reference Manual - Page 5

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Digilent chipKIT Motor Shield Reference Manual
chipKIT™ Motor Shield™ Reference Manual
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The PIC32MX320 microcontroller on the Uno32 provides for two independent I
C interfaces. The Motor Shield is
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designed to provide access to one of these interfaces, I
C #1 (SCL1, SDA1). I
C #1 is accessed through the standard
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chipKIT Wire library. Connector J21 provides access to I
C port #1.
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Connector J21 can be used to extend the I
C bus off of the board to connect to external I
C devices. This is a
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standard 2x4 pin header connector with 0.100" spaced pins. It provides access to the I
C signals, SCL1 and SDA1,
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plus VCC3V3 and ground. The VCC3V3 can be used to power external I
C devices.
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The I
C bus uses open collector drivers to allow multiple devices to drive the bus signals. This means that pull-up
resistors must be provided to supply the logic high state for the signals. The Motor Shield provides 2.2Kohm pull-
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up resistors on I
C #1.
Generally, only one set of pull-ups are used on the bus. Jumpers JP7 and JP8 can be used to disable the on-board
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pull-ups on I
C #1 if a different value is needed or some other device on the bus is providing the pull-ups or if I
C #1
isn't being used and the pull-ups are interfering with the use of the pins. The on-board pull-ups are enabled by
install shorting blocks on JP7 and JP8. Removing the shorting blocks disables the pull-ups.
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Digilent has several small I/O modules available that can be connected using the I
C connector. These include a 3-
axis accelerometer, 4-channel, 12-bit A/D converter, serial character LCD panel, 3-axis gyroscope, and a real-time
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clock/calendar. The on-board I/O expander is also controlled via I
C #1.
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I/O Expander
The Motor Shield contains an I/O expander module that gives access to 4 LEDs, 2 pushbuttons, and 2
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jumper-switches. The I/O expander is controlled via I
C #1. The outputs can be easily controlled using the
Motor Shield MPIDE library.
CHIPKIT and the CHIPKIT Logo are trademarks or registered trademarks of Microchip Technology Incorporated in the U.S. and
other countries, and are used under license.
Copyright Digilent, Inc. All rights reserved.
Page 5 of 8
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