Can Interface - Digilent chipKIT Pro MX7 Reference Manual

chipKIT™ Pro MX7 Board Reference Manual
When operating as a USB host, the PIC32MX795 microcontroller controls application of power to the connected
device via the VBUSON control pin. The VBUSON signal is connected to the circuit net labeled P32_VBUSON in the
schematic. Bus power is applied to the attached USB device by driving the VBUSON pin high. Power is removed
from the device by driving the VBUSON pin low. The VBUSON pin is accessed via bit 3 of the U1OTGCON register.
The VBUSON pin drives the enable input of a Texas Instruments TPS2051B Current-Limited Power Distribution
Switch to control the application of USB power to the host connector. This switch has over-current detection
capability and provides an over-current fault indication by pulling the signal P32_USBOC low. The over-current
output indication can be monitored via I/O Port D pin 13 (RD13) on the PIC32MX795 microcontroller. This pin can
function as change notification pin 19 (CN19), so that a change notification interrupt can be used to detect the
overcurrent condition.
Details about the operation of the TPS2051B can be obtained from the data sheet available at the Texas
Instruments web site.
The Microchip Applications Library, MAL, available on the Microchip web site contains USB driver code for
implementing either USB host devices or USB function devices. This library contains numerous examples
demonstrating both device and host operation of PIC32 microcontrollers. With minor modification or
configuration, these reference designs are suitable to use for developing USB firmware for the chipKIT Pro MX7
board.
Digilent has USB libraries available that can be used to develop both USB device and USB host applications when
using the board with the MPIDE development environment. These libraries are built on a custom version of the
Microchip Applications Library and can be downloaded from the chipKIT Pro MX7 product page on the Digilent
web site.
The Digilent chipKIT libraries contain examples illustrating various USB host and device applications.
8

CAN Interface

The Controller Area Network (CAN) is a control networking standard originally developed for use in automobile
systems, but has since become a standard used in various industrial control and building automation networking
applications as well.
The PIC32MX795 microcontroller contains two independent CAN network controllers. These CAN controllers in
combination with two Microchip MCP2551 CAN transceivers allow the chipKIT Pro MX7 board to operate on up to
two independent CAN networks. Refer to the PIC32MX5XX/6XX/7XX Family Data Sheet and the PIC32 Family
Reference Manual, Section 34, Controller Area Network (CAN), plus CAN network documentation for information
on operation of the CAN controllers and CAN networking in general.
The Microchip C32 peripheral library, plib, provides basic support for all CAN operations using the CAN controllers
in the PIC32MX795 microcontroller.
Digilent has a basic CAN library available for use with the MPIDE software environment. This library can be
downloaded from the chipKIT Pro MX7 product page on the Digilent web site.
The PIC32MX795 microcontroller provides two sets of pins that can be used to connect the CAN controllers to the
external transceivers. The chipKIT Pro MX7 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:
Copyright Digilent, Inc. All rights reserved.
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