Digilent 410-229P - Manual (Page 2)

chipKIT Pmod Shield-Uno Reference Manual
www.digilentinc.com page 2 of 7
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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: I 2 C #1 Daisy Chain Connector
This is a 2x4 pin header connector that provides access to the I 2 C signals SDA and SCL as well as
power from the 3.3V power bus and ground. This can be used to extend the I
2
C bus off of the board
and to power external I 2 C devices. Digilent has cables and a selection of I 2 C 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.
I
2
C Busses and Connectors
The Inter-Integrated Circuit (I
2 C) Interface provides a medium speed (100K or 400K bps) synchronous
serial communications bus. The I 2 C 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 I
2
C interface.
The PIC32MX320 microcontroller on the Uno32 provides for two independent I
2 C interfaces. The
Pmod Shield-Uno is designed to provide access to both of these interfaces I 2 C #1 (SCL1, SDA1) and
I
2
C #2 (SCL2, SDA2). I
2
C #1 is the bus accessed through the standard chipKIT Wire library.
Connector J2 provides access to I 2 C port #1 while access to I 2 C port #2 is available on several of the
connectors of the Pmod Shield-Uno.
Connector J2 can be used to extend the I
2
C busses off of the board to connect to external I
2
C
devices. This is a standard 2x4 pin header connector with 0.100” spaced pins. It provides access to
the I 2 C signals, SCL and SDA, plus VCC3V3 and ground. The VCC3V3 can be used to power
external I
2
C devices.
The I
2 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 Pmod Shield-
Uno provides 2.2Kohm pull-up resistors on I
2
C #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 I
2 C #1 if a different value is needed or some other device on the bus