Digilent 410-273P-KIT - Manual (Page 10)

WF32 Reference Manual
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Page 10 of 24
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 USBOC low. The over-current output pin can be monitored via
the INT3/RA14 pin on the PIC32MX695 microcontroller. This signal appears on connector J7, pin 1 on the board,
and is chipKIT digital pin 8. Details about the operation of the TPS2051B can be obtained from the data sheet
available at
www.ti.com .
Both the VBUSON and the INT3/RA14 signals connect to the TPS2051B through jumpers JP11, and JP9,
respectively. When operating as a USB host, both jumpers should be shorted with shorting blocks. Pin A7 will be
unusable as an analog input and will be driven as an output. To monitor the over-current output pin of the
TPS2051B, us the attachInterrupt() function to set INT3/RA14 (pin 8) as an external interrupt.
The PIC32 USB controller can be accessed using the chipKIT USB libraries for use within the MPIDE environment.
When using the WF32 outside the MPIDE environment, the Microchip Application Library provides USB stack code
that can be used with the board. 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 WF32 Shield.
9 SD Card Interface
The micro-SD card connector provides the ability to access data stored on micro-SD sized flash memory cards using
the SD card library provided as part of the MPIDE software system.
The SD card is accessed using an SPI interface on PIC32 microcontroller pins dedicated to this purpose. The SD
library uses a ‘bit-banged’ software SPI implementation to talk to SD cards.
On the WF32 board, the I/O pins used to communicate with the SD card are dedicated to that function and not
shared with other uses.
10 Peripheral I/O Functions
The PIC32 microcontroller on the WF32 board provides a number of peripheral functions. The following
peripherals are provided:
10.1 UART Ports
UART 1: Asynchronous serial port. Pin 0 (RX), Pin 1 (TX). This is accessed using the runtime object: Serial. These
pins are connected to I/O connector J9 and are also connected to the FT232RQ USB serial converter. It is possible
to use these pins to connect to an external serial device when not using the USB serial interface. This uses UART1
(U1RX, U1TX) on the PIC32 microcontroller.
UART 4: Asynchronous serial port. Pin 39 (RX), Pin 40 (TX). This is accessed using the runtime object: Serial1. This
uses UART4 (U24X, U4TX) on the PIC32 microcontroller.