Digilent Wi-FIRE Reference Manual

Wi FIRE Reference Manual

Building on the previous successes with the chipKIT WF32, the Wi-FIRE uses the same 43
available I/O pins, 12 analog inputs, 3.3 operating voltage, 4 user LEDs, potentiometer,
buttons, uses MRF24 on-board wireless module, microSD Card, dedicated SPI Signals and
high efficiency switching 3.3V switching power supply for low-power operation. Where the
boards differ is in what the PIC32MZ processor can deliver.

The Wi-FIRE is significantly faster than its WF32 counterpart, with 200 MHz operation
speed, 2MB of Flash, 512kB RAM, High-Speed USB and a 50MHz SPI. The PIC32MZ core
includes the MIPS M5150 CPU Core from Imagination Technologies. The M5150 is a highly
efficient, compact core that is optimized for cloud-connected based projects, using
Imagination Technologies' FlowCloud software.

The Wi-FIRE can be programmed using MPIDE and with the addition of a compatible in­system programmer/debugger, can be used with the more fully featured/advanced
Microchip MPLAB® X IDE.

Features

 Microchip® PIC32MZ2048EFG100 microcontroller (200 MHz () 32-bit MIPS M5150, 2MB Flash, 512K RAM ())
 Microchip MRF24WG0MA WiFi module
 MicroSD card connector
 USB 2.0 Hi-Speed OTG controller with A and micro-AB connectors

MHz () SPI

 50
 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
 200Mhz 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

1. Wi-FIRE Hardware Overview

Call Out Component Description

1 IC3- Microchip MRF24WG0MA WiFi Module

2 User Buttons

3 JP1- Microchip Debug Tool Connector

4 J6- I2C Signals

5 BTN3- Reset

6 JP2- Reset Disable

7 J7- Digital Signal Connector

8 PIC32 Microcontroller

9 Potentiometer

10 J10- Digital Signal Connector

11 User LEDs

Call Out Component Description

12 JP6- USB Host or OTG Select

13 J9- SPI Connector

14 J12- USB Connectors

15 JP8- Hos USB Bus Power Enable

16 JP7- USB Overcurrent Detect

17 J8- Analog and Digital Signal Connector

18 JP9- 3.3v / 5.0v Shield Voltage Select

19 J5- Shield Power Connector

20 J17- 5.0V Regulator Configuration

21 J16- Power Select Jumper

22 J13- Micro SD Connector

23 J15- External Power Connector

24 J14- External Power Connector

25 J4- USB- UART Handshaking Signals

26 USB connector for USB Serial Converter

27 Serial Communication LEDs

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2. MPIDE and USB Serial Communications

The WiFire board is designed to be used with the Multi-Platform IDE (MPIDE;), the MPIDE
development platform was created by modifying the Arduino™ IDE. It and is backwards-compatible
with the Arduino IDE. Links for where to obtain the MPIDE installation files, and as well as
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
WiFire board. The serial port on the WiFire board is implemented using an FTDI FT232RQ USB
serial converter. Before attempting to use the MPIDE to communicate with the WiFire, the
appropriate USB device driver must be installed.

The WiFire 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 WiFire 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 JP2, which can be disconnected. JP2 is normally
shorted, but if the shorting block is removed, the automatic reset operation will be disabled.

Two red LEDs (LD5 and LD6) will blink when data is being sent or received between the WiFire and
the PC over the serial connection. The header connector J4 provides access to the other serial
handshaking signals provided by the FT232RQ. Connector J4 is not loaded at the factory and can
be installed by the user to access these signals.

3. Power Supply

The WiFire is designed to be powered via USB (J1), from an external power supply (J14 or J15), or
from the USB OTG receptacle (J11). Jumper block J16 is used to select which power supply is used.
The power supply voltage selected by J16 is applied to the unregulated power bus, VU.

In order to operate the WiFire as a USB device powered from the USB serial interface, (connector
J1), place a shorting block in the UART position of jumper block J16. To operate the WiFire from an
external power supply, attach the power supply to either J14 or J15 and place a shorting block in the
EXT position of J16. Be sure to observe correct polarity when connecting a power supply to J14, as
a reversed connection could damage the board. To operate the WiFire as a USB powered device
from the USB OTG connector (J11), place a shorting block on the USB position of J16. 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 WiFire provides two voltage regulators, a 3.3V regulator and

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a 5V regulator. All systems on the WiFire 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 and to supply USB 5.0Vv when the WiFire is used as a USB Host. The 5V
regulator can be completely disabled if it is not needed for a given application.

When a shield is used, connectoer J5 provides power to the shield. Connectoer J5 pin 8 provides
VIN as applied by the external power source J14 or J15. If no power is provided to J14 or J15, VIN
will not be powered. For most shields, pin 5 on connector J5 would provide 5.0Vv to the shield;
however, the WiFire is not 5v tolerant and it would be very easy for a shield to destroy an input if

5.0Vv were applied to the PIC32MZ. For this reason, JP9 was added to control the voltage supplied
to the shield’s 5Vv source. By default, JP9 is loaded to supply only 3.3Vv on the 5.0Vv pin so that
the shield does not get 5Vv and thus cannot inadvertently apply 5.0Vv to any input to the WiFire. If
the shield requires 5.0Vv to operate, the shield will not work when 3.3Vv is applied; JP9 must be
selected to provide 5.0Vv for the shield to work. However, extreme caution should be used when
selecting 5.0Vv on JP9 to ensure that the shield will observe IOREF and not supply 5.0Vv to any
input to the WiFire; as this will damage the input to the PIC32MZ on the WiFire.

The WiFire board is designed for low power operation and efficient use of battery power;, as such a
switching mode voltage regulator is used for the 3.3V power supply. This switching mode regulator is
made up of a Microchip MCP16301 and associated circuitry, which. 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
(J5) to provide 3.3V power to external circuitry, such as shields.

The 5V regulator section provides a low dropout linear regulator. The 5.0 regulator is provided for
powering external circuitry that needs a 5V power supply, such as providing for USB 5.0Vv when the
WiFire is used as a USB hHost, or to provide 5.0Vv to the shield on J5 with JP9 selected to 5.0v.
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. However, if the 5.0Vv regulator is completely disable by removing all
jumpers on J17, the external input voltage applied to J14 or J15 may be as high as the 30V as
limited by the switching mode 3.3Vv regulator.

The input voltage to the 5V regulator 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 as well asand internal thermal protection and will shut
down automatically to prevent damage.

The 5V regulator selection on JP17 provides four 5V power configurations:

1. 5V regulator completely disabled and no 5V power available

2. 5V regulator bypassed and 5V provided from an external 5V power supply, such as USB

3. on-board 5V regulator used to provide 5V power

4. External 5V regulator used to regulate VU and provide 5V power

Jumper block J17 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 J17:

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To completely disable operation of the on-board linear regulator, remove all shorting blocks from
J17. 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:

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Note: In this case, when J16 is in the EXT position, and J17 is jumpered to regulate the external
input, do not apply more than 18V;. tThis 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:

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An external 5V regulator can be used. This would be desirable, for example, when operating from
batteries. An external switching 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 50 is then used to turn on/off the external regulator.

The PIC32MZ microcontroller is rated to use a maximum of 60mA of current when operating at 200
MHhz. The MRF24WG0MA WiFi module typically consumes a maximum of 237mA when
transmitting. This allows approximately 303mA of current to power the remaining 3.3V circuitry on
the WiFire board and external circuitry powered from the VCC3V3 bus. No circuitry on the WiFire
board is powered from the VCC5V0 power bus, leaving all current available from the 5V regulator to
power external circuitry and the USB 5.0Vv power bus when the WiFire is used as a USB Host.

The POWER connector (J5) is used to power shields connected to the WiFire board. Pin 1 is
unconnected, the following pins are provided on this connector:

 IOREF (pin 2): This pin is tied to the VCC3V3 bus.
 RST (pin 3): This connects to the MCLR pin on the PIC32 microcontroller and can be used to

reset the PIC32.

 3V3 (pin 4): This routes the 3.3V power bus to shields.
 5V0 (pin 5): This routes 3.3V or 5.0V power to shields depending on the position of JP9.
 GND (pin 6, 7): This provides a common ground connection between the WiFire and the

shields. This common ground is also accessible on connectors J2 and J3.

 VIN (pin 8): This connects to the voltage provided at the external power supply connectors

(J14 and J15). This can be used to provide unregulated input power to the shield. It can also
be used to power the WiFire board from the shield instead of from the external power
connector. If no power is supplied at J14 or J15 or from the shield, VIN will not have any
power on it.

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4. 5V Compatibility

The PIC32 microcontroller operates at 3.3V. The original Arduino boards operate at 5V, as do many
Arduino shields.

There are two issues to consider when dealing with 5V compatibility for 3.3V logic. The first is
protection of 3.3V inputs from damage caused by 5V signals. The second is whether the 3.3V output
is high enough to be recognized as a logic high value by a 5V input.

The digital I/O pins on the PIC32 microcontroller are 5V tolerant. The, whereas the analog capable
I/O pins are not 5V tolerant. There are 48 analog capable I/O pins on the PIC32MZ, and this applies
to most GPIO pins on the processor. Historically, clamp diodes and current limiting resistors have
been used to protect the analog capable I/O from being damaged; but because of the large number
of analog capable I/Os, and because clamp diodes and resistors will limit the maximum speed at
which these I/Os will operate,; it was decided that the WiFire would not be 5V tolerant. Instead, JP9
was added to allow for the 5V0 bus to the shield to be selectable between 3.3Vv or 5.0Vv. If 5.0Vv is
selected, great care must be used to ensure that no input to the PIC32MZ exceeds 3.6Vv; as that
will damage the PIC32MZ.

The minimum high-voltage output of the PIC32 microcontroller is rated at 2.4V when sourcing 12mA
of current. When driving a high impedance input (typical of CMOS logic) the output high voltage will
be close to 3.3V. Some 5V devices will recognize this voltage as a logic high input, and some won’t.
Many 5V logic devices will work reliably with 3.3V inputs.

5. Input/ Output Connections

The WiFire board provides 43 of the I/O pins from the PIC32 microcontroller at pins on the
input/output connectors J6, J7, J8, J9, and J10.

The PIC32 microcontroller can source or sink a maximum of 15mA on all digital I/O pins; however,
some pins can source or sink 25mA or even 33mA;, check with the PIC32MZ datasheet for more
information. To keep the output voltage within the specified output voltage range (VOL 0.4V, VOH

2.4V) the pin current must be restricted to +/-10mA on the 15mA pins, or for the higher current pins
check the PIC32MZ datasheet for the maximum currents. The maximum current that can be sourced
or sunk across all I/O pins simultaneously is +/-150mA. The maximum voltage that can be applied to
any I/O pin is 3.6V. For more detailed specifications, refer to the PIC32MZ Data Sheetdatasheet
available from

Connectors J7 and J10 are 2×8 female pin header connectors that provide digital I/O signals. The
outer row of pins (closer to the board edge) corresponds to the I/O connector pins on an Arduino
Uno or Duemilanove board. The inner row of pins provides access to the extra I/O signals provided
by the PIC32 microcontroller.

www.microchip.com.

Connector J8 is a 2×6 female pin header connector that provides access to the analog input pins on
the microcontroller. The outer row of pins corresponds to the six analog pins on an Arduino Uno or
Duemilanove. The inner row of pins is for the additional I/O signals provided by the PIC32
microcontroller. The analog pins on J8 can also be used as digital I/O pins.

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The chipKIT/Arduino system uses logical pin numbers to identify digital I/O pins on the connectors.
The logical pin numbers for the I/O pins on the WiFire are 0-42. These pin numbers are labeled in
the silk screen on the board. Additional pins 43-70 allow access to the on board components such
as the uSD, MRF24 WiFi radio, User LEDs / BTNs, and POT.

Pin numbers 0-13 are the outer row of pins on J10 and J7, from right to left. Pin numbers 14-19 are
the outer row of pins on J8, from left to right. Pins 20-25 are the inner row of pins on J8, from left to
right. Pin numbers 26-41 are the inner row of pins on J10 and J7, from right to left. Pin 42 is the pin
labeled A on J7. This pin is normally the reference voltage for the microcontroller’s A/D converter,
but can also be used as a digital I/O pin.

In addition to the connector pin, Pin 13 also connects to the user LED LD1. Pin 43, 44, and 45
connect to user LEDs LD2, LD3, and LD4. Pins 43-45 do not attach to any connector. Pins 46 and
47 connect to Buttons BTN1 and BTN2 and do not attach to any connector.

The analog inputs on connector J8 are assigned pin numbers. The outer row of pins on J8 is analog
inputs A0-A5. The inner row of pins is A6-A11. These pins are also assigned digital pin numbers;
A0-A5 are digital pins 14-19, and A6-A11 are 20-25.

6. 802.11b/g Interface

The 802.11b/g compatible WiFi interface on the WiFire is provided by a Microchip MRF24WG0MA
WiFi module. This module provides the radio transceiver, antenna, and 802.11 compatible network
firmware.

The MRF24WG0MA firmware provides the 802.11 network protocol software support. The DEIPcK
and DEWFcK libraries provide the TCP/IP network protocol support that works with the 802.11
protocol support provided by the WiFi module.

The primary communications interface with the MRF24WG0MA WiFi module is a 4 wire SPI bus.
This SPI bus uses SPI4 in the PIC32 microcontroller, and this SPI controller is dedicated to use for
communications with the WiFi module

The WiFi module supports SPI clock speeds up to 25MHz. In addition to the SPI interface, the
interface to the WiFi module also includes a reset signal, an interrupt signal and a hibernate signal.
The active low RESET signal is used to reset the WiFi module The external interrupt signal, INT, is
used by the module to signal to the host microcontroller that it needs servicing by the microcontroller
software. The INT signal on the WiFi module is connected to external interrupt INT4 on the PIC32
microcontroller and is not routed to any connector. The active low HIBERNATE signal is used to
power the WiFi module down and puts it into a low power state.

The interface signals to the WiFi module are controlled by the network libraries and are not normally
accessed by the user sketch. Refer to the schematic for the WiFire board for details on these
connections.

More detailed information about the operation of the MRF24WG0MA can be obtained from the
manufacturer data sheet available from

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www.microchip.com.