Digilent chipKIT Network Shield Manuale di riferimento e guida all'uso - Pagina 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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