Digilent 410-229P User Manual

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Revision: November 7, 2012

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Overview

The chipKIT Pmod Shield-Uno is an
input/output expansion board for use with the
chipKIT Uno32™ and chipKIT uC32™. It
provides the additional circuitry and connectors
to allow Digilent peripheral modules (Pmods™)
to be used with the Uno32 and uC32.

The Pmod Shield-Uno has five 2x6 Digilent
Pmod connectors. It also provides access to
the I/O connectors available on the Uno32 as
well as connecting to the I2C bus supported by
the Uno32 and uC32.

The Pmod Shield-Uno has the same form
factor as the Uno32 and uC32 boards.

Features include:

 five 2x6 Digilent Pmod connectors
 one 6-pin header connector for SPI
 one I2C daisy chain connector
 4 user LEDs
 Standard chipKIT Shield connectors

Functional Description

The Pmod Shield-Uno is designed to be used with the chipKIT Uno32 board. When used in
combination, the two boards provide the necessary supporting hardware and connectors to make use
of most Digilent PmodsTM. The rest of this document will only reference the Uno32, however, the
shield can also be used with the chipKIT uC32.

The Pmod Shield-Uno has the following connectors.

J1 & J3: Digital Signal Pass-Through Connectors

This connector provides most of the signals used by the Uno32 board to the Pmod Shield-Uno board.
The remaining signals are passed through the Pmod Shield-Uno.

J6: SPI #2 Connector

This connector provides access to the SPI signals MISO, MOSI, SCK, and SS.

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chipKIT Pmod Shield-Uno Reference Manual

JA-JE: Digilent Pmod Connectors

These connectors provide access to the signals of the Uno32 in a form factor which readily allows
Digilent Pmods to be connected.

J2: I2C #1 Daisy Chain Connector

This is a 2x4 pin header connector that provides access to the I2C signals SDA and SCL as well as
power from the 3.3V power bus and ground. This can be used to extend the I2C bus off of the board
and to power external I2C devices. Digilent has cables and a selection of I2C peripheral modules that
can be accessed using this connector.

J4: Analog Signal Pass-Through Connector

This connector passes the analog input pins on the Uno32 through the Pmod Shield-Uno board.

J5: Power Pass-Through Connector

This connector passes the power connector from the Uno32 through the Pmod Shield-Uno board, and
powers the Pmod Shield-Uno from the Uno32.

I2C Busses and Connectors

The Inter-Integrated Circuit (I2C) Interface provides a medium speed (100K or 400K bps) synchronous
serial communications bus. The I2C interface provides master and slave operation using either 7 bit or
10 bit device addressing. Each device is given a unique address, and the protocol provides the ability
to address packets to a specific device or to broadcast packets to all devices on the bus. Refer to the
Microchip PIC32MX3XX data sheet and the PIC32 Family Reference Manual for detailed information
on configuring and using the I2C interface.

The PIC32MX320 microcontroller on the Uno32 provides for two independent I2C interfaces. The
Pmod Shield-Uno is designed to provide access to both of these interfaces I2C #1 (SCL1, SDA1) and
I2C #2 (SCL2, SDA2). I2C #1 is the bus accessed through the standard chipKIT Wire library.
Connector J2 provides access to I2C port #1 while access to I2C port #2 is available on several of the
connectors of the Pmod Shield-Uno.

Connector J2 can be used to extend the I2C busses off of the board to connect to external I2C
devices. This is a standard 2x4 pin header connector with 0.100” spaced pins. It provides access to
the I2C signals, SCL and SDA, plus VCC3V3 and ground. The VCC3V3 can be used to power
external I2C devices.

The I2C 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 Pmod Shield­Uno provides 2.2Kohm pull-up resistors on I2C #1.

Generally, only one set of pull-ups are used on the bus. Jumpers JP10 and JP11 can be used to
disable the on-board pull-ups on I2C #1 if a different value is needed or some other device on the bus

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chipKIT Pmod Shield-Uno Reference Manual

is providing the pull-ups or if I2C #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 JP10 and JP11. Removing the
shorting blocks disables the pull-ups.

Digilent has several small I/O modules available that can be connected using the I2C connector.
These include a 3-axis accelerometer, 4-channel, 12-bit A/D converter, serial character LCD panel, 3­axis gyroscope, real-time clock/calendar, and an I/O expander.

SPI Connector

The SPI connector pins are as follows: Pin 1 (MISO), Pin 3 (SCK), Pin 4 (MOSI), and Pin 5 (SS).
These signals also appear on connector J8 of the Uno32.

Jumpers JP5 and JP7 on the Uno32 are used to select whether the Uno32 operates as a Master
(transmit on MOSI, receive on MISO) or a Slave (transmit on MISO, receive on MOSI) device. The
shorting blocks on JP5 and JP7 are normally placed in the Master position for the Uno32 to function
as an SPI master. Also, jumper JP4 on the Uno32 is used to select PWM output (in RD4 position) or
the SPI SS function on Pin 5 (in RG9 position).

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