Digilent MX4cK Manuel d'utilisateur télécharger pdf (Page 15)

Cerebot MX4cK Reference Manual

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When operating as a USB host, the

PIC32MX460 microcontroller controls

application of power to the connected device

via the VBUSON control pin. Bus power is

applied to the 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.

Pin 20 of the PIC32MX460 microcontroller is

used for the VBUSON function. Place the

shorting block in the VBUSON position of

jumper block J16 when using the Cerebot

MX4cK for USB host operation.

The VBUSON pin drives the enable input of a

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. Jumper JP5 is used

to enable monitoring of the overcurrent fault

indication. The over-current output pin can be

monitored via the INT2/RE9 pin on the

PIC32MX460 microcontroller when a shorting

block is installed on JP5. The INT2/RE9 pin is

also connected to Pmod connector JE, pin 7

(JE-07). Pmod connector pin JE-07 should not

be used when using INT2/RE9 to monitor the

USB overcurrent fault indicator. Remove the

shorting block from JP5 to restore normal

operation of JE-07.

Details about the operation of the TPS2051B

can be obtained from the data sheet available

at the Texas Instruments web site.

Jumper JP10 can be used to disconnect the

USB load switch, IC6, when the board is

operating from a power supply with a higher

voltage than 5V. When the Cerebot MX4cK is

operating as a USB host, a shorting block must

be in place on JP10.

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 Cerebot MX4cK 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 chipKIT MPIDE development environment.

These libraries can be downloaded from the

Cerebot MX4cK product page on the Digilent

web site.

The Digilent chipKIT libraries contain examples

illustrating various USB host and device

applications.

UART Interface

The PIC32MX460 microcontroller provides two

UART interfaces, UART1 and UART2. The

UARTs can provide either a 2-wire or a 4-wire

asynchronous serial interface. The 2-wire

interface provides receive (RX) and transmit

(TX) pins. The 4-wire interface includes

request-to-send (RTS) and clear-to-send

(CTS) in addition to receive and transmit.

UART1 can be accessed from Pmod connector

JE and UART2 can be accessed from Pmod

connector JH using the following pins:

• U1CTS JE-01

• U1TX JE-02

• U1RX JE-03

• U1RTS JE-04

• U2CTS JH-01

• U2TX JH-02

• U2RX JH-03

• U2RTS JH-04

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