Digilent Max32 Справочное руководство - Страница 10

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Max32™ Board Reference Manual

Some Arduino shields, notably, the Ethernet shield, connect J13 pin 5 to the reset net on pin 1 of connector J10.

This causes the processor to be reset each time an attempt is made to access the SPI port. Jumper JP2 can be used

to break the connection between J13 pin 5 and reset when using Arduino shields that make this connection. JP2

has a cuttable trace on the bottom of the board that can be cut to break the connection between SPI SS and reset.

JP2 is not loaded at the factory. To restore the connection, solder a 2-pin header at the JP2 position and install a

shorting block.

A reset button is at the upper left corner of the board. Pressing this button will reset the PIC32 microcontroller.

3. 6 Advanced Peripheral Devices

The PIC32MX795F512L microcontroller on the Max32 board has several peripheral devices for advanced

communications capabilities. These peripheral devices require additional hardware that isn't provided on the

Max32 board. This additional hardware must be provided by a shield board (such as the Digilent Network Shield)

connected to the Max32.

These advanced peripheral functions make use of various I/O pins for their operation. Most of the I/O pins used by

the advanced peripheral devices are located on connectors J8 and J9. When these pins are being used by the

advanced peripheral functions they are not available for other uses.

USB: The USB OTG controller allows using the Max32 board to implement a USB device, USB host, or USB OTG

host/device. The following pins are used by the USB interface: Pin 27 (D+), Pin 26 (D-), Pin 25 (USBID), Pin 24

(VBUS).

Pin 24 (VBUS) can be used by a self-powered USB device to monitor the presence of bus voltage on the USB bus.

This pin on the PIC32 microcontroller is an analog input pin used by the USB controller, and is not useable as a user

I/O pin even when not using the USB controller.

10/100 Ethernet MAC: The Ethernet MAC requires an external PHY to complete the implementation of an

Ethernet network port. The Ethernet MAC constructs the digital format of packets being sent and performs the

checking and buffering of packets being received. The PHY provides the physical interface and translates the digital

signals used by the MAC into the analog voltages used on the Ethernet cable.

There are two common interfaces used between an Ethernet MAC and the PHY: MII and RMII. The MAC in the

PIC32 supports either interface, but the Max32 board is designed to use the RMII interface.

The RMII Ethernet PHY interface uses the following pins: Pin 53 (EREFCLK), Pin 49 (EMDC), Pin 48 (EMDIO), Pin 47

(ETXEN), Pin 46 (ETXD0), 45 (ETXD1), Pin 43 (ECRSDV), Pin 42 (ERXD0), Pin 41 (ERXD1), Pin 40 (ERXERR), and Pin 7

(NRST).

CAN1, CAN2: The CAN controllers allow the Max32 to participate in one or two CAN (Controller Area Network)

networks. CAN is a networking standard that was developed for use in the automotive industry and is now also use

in building automation and other industrial applications. The CAN controllers in the PIC32 microcontroller require

external CAN transceivers to connect to the network wiring.

The CAN1 interface uses the following pins: Pin 15 (AC1RX), Pin 14 (AC1TX). Note that these pins are also used by

UART3.

The CAN2 interface uses the following pins: Pin 23 (AC2RX), Pin 21 (AC2TX).

The PIC32 microcontroller is designed to allow one of two sets of pins to be used by the CAN controllers to connect

to the transceivers. The Max32 board is designed to use the alternate sets of pins.

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