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chipKIT™ WF32™ Board Reference Manual
Revised October 9, 2015
This manual applies to the chipKIT WF32 rev. B
Overview
The chipKIT WF32 is based on the popular Arduino™ open-source hardware prototyping platform and adds the
performance of the Microchip PIC32 microcontroller. The WF32 is the first board from Digilent to have a WiFi
MRF24 and SD card on the board both with dedicated signals. The WF32 board takes advantage of the powerful
PIC32MX695F512L microcontroller. This microcontroller features a 32-bit MIPS processor core running at 80Mhz,
512K of flash program memory, and 128K of SRAM data memory.
The chipKIT WF32 board.
Microchip® PIC32MX695F512L microcontroller (80
Mhz 32-bit MIPS, 512K Flash, 128K SRAM)
Microchip MRF24WG0MA WiFi module
Micro SD card connector
USB 2.0 OTG controller with A and micro-AB
connectors
43 available I/O pins
four user LEDs
PC connection uses a USB A > mini B cable (not
included)
12 analog inputs
3.3V operating voltage
80Mhz operating frequency
7V to 15V input voltage (recommended)
30V input voltage (maximum)
0V to 3.3V analog input voltage range
High efficiency, switching 3.3V power supply
providing low power operation
The WF32 can be programmed using the Multi-Platform Integrated Development Environment (MPIDE), an
environment based on the original Arduino IDE, modified to support PIC32. It contains everything needed to start
developing embedded applications. The WF32 features a USB serial port interface for connection to the MPIDE and
can be powered via USB or by an external power supply. In addition, the WF32 is fully compatible with the
®
advanced Microchip MPLAB IDE and works with all MPLAB compatible in-system programmer/debuggers, such as
the Microchip PICkit™3 or the Digilent chipKIT PGM. The WF32 is easy to use and suitable for both beginners and
advanced users experimenting with electronics and embedded control systems.
DOC#: 502-273
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
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chipKIT™ WF32™ Board Reference Manual
1
ChipKIT WF32 Hardware Overview
The WF32 has the following hardware features:
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Call Out
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Component Description
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Call Out
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Component Description
J13- USB Connectors
JP9- USB Overcurrent Detect
JP11- Hos USB Bus Power Enable
J8- Analog and Digital Signal Connector
JP5, JP4- Analog or
C Select Jumper
IC3- Microchip MRF24WG0MA WiFi Module
User Buttons
JP3- Microchip Debug Tool Connector
J6-
Signals
BTN1- Reset
JP1- Reset Disable
J7- Digital Signal Connector
JP3- Pin 10 Signal Select Jumper
PIC32 Microcontroller
Potentiometer
J9- Digital Signal Connector
J3- Shield Power Connector
J16- 5.0V Supply Select
J15- Power Select Jumper
J11- Micro SD Connector
J17- External Power Connector
J14- External Power Connector
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
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chipKIT™ WF32™ Board Reference Manual
12
13
14
15
User LEDs
JP6,7- SPI Master/ SPI Slave Select
J10- SPI Connector
JP10- USB Host or OTG Select
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28
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J2- USB- UART Handshaking Signals
USB connector for USB Serial Converter
Serial Communication LEDs
2
MPIDE and USB Serial Communications
The WF32 board is designed to be used with the Multi-Platform IDE (MPIDE), the MPIDE development platform
was created by modifying the Arduino™ IDE. It is backwards-compatible with the Arduino IDE. Links for where to
obtain the MPIDE installation files and instructions for installing MPIDE can be found at www.chipkit.net/started.
The MPIDE uses a serial communications port to communicate with a boot loader running on the WF32 board. The
serial port on the WF32 board is implemented using an FTDI FT232RQ USB serial converter. Before attempting to
use the MPIDE to communicate with the WF32, the appropriate USB device driver must be installed.
The WF32 board uses a standard mini-USB connector. Generally, a USB A to mini-B cable is used for connection to
a USB port on the PC.
When the MPIDE needs to communicate with the WF32 board, the board is reset and starts running the boot
loader. The MPIDE then establishes communications with the boot loader and uploads the program to the board.
When the MPIDE opens the serial communications connection on the PC, the DTR pin on the FT232RQ chip is
driven low. This pin is coupled through a capacitor to the MCLR pin on the PIC32 microcontroller. Driving the MCLR
line low resets the microcontroller, which restarts the execution with the boot loader.
This automatic reset action (when the serial communications connection is opened) can be disabled. To disable
this operation, there is a jumper labeled JP1, which can be disconnected. JP1 is normally shorted, but if the
shorting block is removed, the automatic reset operation will be disabled.
Two red LEDs (LD1 and LD2) will blink when data is being sent or received between the WF32 and the PC over the
serial connection.
The header connector J2 provides access to the other serial handshaking signals provided by the FT232RQ.
Connector J2 is not loaded at the factory and can be installed by the user to access these signals.
3
Power Supply
The WF32 is designed to be powered via USB (J1), from an external power supply (J14 or J17), or from the USB OTG
receptacle (J12). Jumper block J15 is used to select which power supply is used. The power supply voltage selected
by J15 is applied to the unregulated power bus, VU.
In order to operate the WF32 as a USB device powered from the USB serial interface, connector J1, place a
shorting block in the UART position of jumper block J15. To operate the WF32 from an external power supply,
Copyright Digilent, Inc. All rights reserved.
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chipKIT™ WF32™ Board Reference Manual
attach the power supply to either J14 or J17 and place a shorting block in the EXT position of J15. Be sure to
observe correct polarity when connecting a power supply to J14, as a reversed connection could damage the
board. To operate the WF32 as a USB powered device from the USB OTG connector (J12) place a shorting block on
the USB position of J15. This will normally only be done when running a sketch on the board that programs it to
operate as a USB device. The power supply section in the WF32 provides two voltage regulators, a 3.3V regulator
and a 5V regulator. All systems on the WF32 board itself operate at 3.3V and are powered by the 3.3V regulator.
The 5V regulator is used to provide power for external circuits, such as shields, that require 5V for operation. The
5V regulator can be completely disabled if it is not needed for a given application.
The WF32 board is designed for low power operation and efficient use of battery power, as such a switch mode
voltage regulator is used for the 3.3V power supply. This switch mode regulator is made up of a Microchip
MCP16301 and associated circuitry. It can operate on input voltages from 4V to 30V with up to 96% efficiency, and
is rated for 600mA total current output. The MCP16301 has internal short circuit protection and thermal
protection. The 3.3V regulator takes its input from the unregulated power bus, VU, and produces its output on the
VCC3V3 power bus. The VCC3V3 bus provides power to all on-board systems and is available at the shield power
connector (J3) to provide 3.3V power to external circuitry, such as shields.
The 5V regulator section provides a low dropout linear regulator. No circuitry on the WF32 board uses the 5V
supply. It is provided for powering external circuitry that needs a 5V power supply. This voltage regulator uses an
On Semiconductor NCP1117LP. The NCP1117LP is rated for an output current of 1A. The dropout voltage of the
NCP1117LP is a maximum of 1.4V at 1A output current. The maximum input voltage of the NCP1117LP is 18V. The
recommended maximum operating voltage is 15V.
The input voltage to the 5V regulator section is taken from the VU bus, and the output is placed on the VCC5V0
power bus.
There is a reverse polarity protection diode in the external power supply circuit. Considering the diode drop plus
the forward drop across the regulator, the minimum input voltage to the regulator should be 7V to produce a
reliable 5V output.
For input voltages above 9V, the regulator will get extremely hot when drawing high currents. The NCP1117LP has
output short circuit protection and internal thermal protection and will shut down automatically to prevent
damage.
The 5V regulator section actually provides four 5V power options:
1)
2)
3)
4)
5V regulator completely disabled and no 5V power available;
5V regulator bypassed and 5V provided from an external 5V power supply, such as USB;
on-board 5V regulator used to provide 5V power;
External 5V regulator used to regulate VU and provide 5V power.
Jumper block J16 is used to select these various options and the following diagrams describe the use of J16:
This diagram shows the arrangement of the signals on J16:
LDO In
VU
EN Ext
LDO Out
5V0
GND
LDO In is the input to the on-board linear regulator.
LDO Out is the output of the on-board linear regulator
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chipKIT™ WF32™ Board Reference Manual
VU is the unregulated input voltage selected by the jumper setting jumper block J15.
5V0 is the connection to the VCC5V0 power bus on the WF32 board.
EN Ext is a signal provided to enable an external voltage regulator if one is being used. This would allow the sketch
running on the WF32 to turn on/off the external voltage regulator. When used with an external voltage regulator,
this allows the board to go into an extremely low power operating mode. This signal is connected to Port D, bit 13
(RD13) on the PIC32 microcontroller. This is accessible using digital pin 64.
GND is a connection to the digital ground bus on the WF32 board.
To completely disable operation of the on-board linear regulator, remove all shorting blocks from J16.
To use the on-board 5V regulator, use the provided shorting blocks to connect VU to LDO In, and to connect LDO
Out to 5V0, as follows:
LDO In
VU
EN Ext
LDO Out
5V0
GND
Note:
In this case, when J15 is in the EXT position, and J16 is jumpered to regulate the external input, do not apply
more than 18V. This can destroy the 5.0V regulator.
To bypass the on-board 5V regulator when powering the board from an externally regulator 5V power supply, such
as USB, Use one of the provided shorting blocks to connect VU to 5V0, as follows:
LDO In
VU
EN Ext
LDO Out
5V0
GND
An external 5V regulator can be used. This would be desirable, for example, when operating from batteries. An
external switch mode 5V regulator could be used to provide higher power efficiency than the on-board linear
regulator. In this case, use wires as appropriate to connect VU to the unregulated input of the external regulator.
Connect the regulated 5V output to 5V0. Connect GND to the ground connection of the external regulator.
Optionally, connect EN Ext to the enable input control of the external regulator, if available. This allows the
external regulator to be turned off for low power operation. Digital pin 64 is then used to turn on/off the external
regulator.
The PIC32MX695 microcontroller is rated to use a maximum of 98mA of current when operating at 80Mhz. The
MRF24WG0MA WiFi module typically consumes a maximum of 237mA when transmitting. This allows
approximately 265mA of current to power the remaining 3.3V circuitry on the WF32 board and external circuitry
powered from the VCC3V3 bus. No circuitry on the WF32 board is powered from the VCC5V0 power bus, leaving
all current available from the 5V regulator to power external circuitry.
The POWER connector (J3) is used to power shields connected to the WF32 board. Pin 1 is unconnected, the
following pins are provided on this connector:
IOREF
(pin 2): This pin is tied to the VCC3V3 bus.
P32_RST
(pin 3): This connects to the MCLR pin on the PIC32 microcontroller and can be used to reset the PIC32.
VCC3V3
(pin 4): This routes the 3.3V power bus to shields.
VCC5V0
(pin 5): This routes the 5V power bus to shields.
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
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