Digilent chipKIT Network Shield Reference Manual And User's Guige - Page 7

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chipKIT Network Shield Reference Manual
When using the Max32/Network Shield outside
the MPIDE environment, the Microchip
Application Library provides USB stack code
that can be used with the Max32/Network
Shield. There are reference designs available
on the Microchip web site demonstrating both
device and host operation of PIC32
microcontrollers. These reference designs are
suitable to use for developing USB firmware for
the Max32/Network Shield.
CAN Interfaces
The Controller Area Network (CAN) is a control
networking standard originally developed for
use in automotive systems, but has since
become a standard used in various industrial
control and building automation networking
applications as well.
The PIC32MX795 microcontroller on the
Max32 contains two independent CAN network
controllers. These CAN controllers in
combination with two Microchip MCP2551
CAN transceivers on the Network Shield allow
the Max32/Network Shield to operate on one
or two independent CAN networks.
When not using the MPIDE environment, refer
to the PIC32MX7XX data sheet and the PIC32
Family Reference Manual, plus CAN network
documentation for information on operation of
the CAN controllers and CAN networking in
general.
The PIC32MX795 microcontroller provides two
sets of pins that can be used to connect the
CAN controllers to the external transceivers.
The Max32/Network Shield is designed to use
the alternate (not the standard) pins. This
selection is made using the configuration
variables in the microcontroller, set using a
#pragma config
statement. To select the use
of the alternate interface pins, the following
statement must appear in the main program
module:
#pragma config FCANIO=OFF
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When using the Max32/Network Shield within
the MPIDE environment, the boot loader on the
Max32 boards sets this configuration
automatically, so nothing needs to be done in
this case. When using the boards outside the
MPIDE environment, this configuration setting
is required.
The pins on the PIC32MX795 microcontroller
used by signals for the CAN1 controller to
connect to its transceiver are shared with two
of the signals for UART3B and SPI port 3A.
These signals appear on pins 14 & 15 of
connector J4 on the Max32 board. To recover
the use of these pins if both CAN networks are
not needed, jumpers JP1 and JP5 are provided
on the Network Shield. There are cut-able
traces on the bottom of the board between the
pins of JP1 and JP5. Cut these traces to
disconnect the transceiver for CAN1. To
restore the connection, load two pin headers
for JP1 and JP5 and install shorting blocks on
the two jumpers.
The pins on the PIC32MX795 microcontroller
used by the signals for CAN2 appear on
connector J13 on the Network Shield
(connector J9 on the Max32), pins 15 and 16.
These are digital pins 22 and 23. These pins
are not available for other use when using
CAN2.
There is no standard connector for use with
CAN networks. The Network Shield provides
two 2x6 pin header connectors for access to
the CAN signals. Connector J3 provides
access to the signals for the CAN1 network
controller, and connector J5 provides access to
the signals for CAN2. Refer to the schematic
for the Network Shield board or the tables at
the end of this document for information on the
connectors and signals. Digilent 6-pin or 2x6 to
dual 6-pin cables can be used to daisy chain
Digilent boards together in a CAN network. A
Digilent 6-Pin cable in combination with a
Digilent PmodCON1 Screw Terminal
Connector module can be used to connect the
Max32/Network Shield to other network wiring
configurations.
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