Datasheet

chipKIT™ Wi-FIRE™ Board Reference Manual
Copyright Digilent, Inc. All rights reserved.
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Page 6 of 24
Signals
Description
LDO In
The input to the on-board linear regulator.
LDO Out
The output of the on-board regulator.
VU
The unregulated input voltage selected by the jumper setting jumper block J16.
5V0
The connection to the VCC5V0 power bus on the Wi-FIRE board.
EN Ext
Signal provided to enable an external voltage regulator, if one is being used. This would allow
the sketch running on the Wi-FIRE 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 50.
GND
Connection to the digital ground bus on the Wi-FIRE board.
Table 2. Description of signals on J17.
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:
LDO OutLDO In
VU 5V0
GNDEN Ext
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; 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 OutLDO In
VU 5V0
GNDEN Ext
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 MHz. 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 Wi-FIRE board and external circuitry
powered from the VCC3V3 bus. No circuitry on the Wi-FIRE board is powered from the VCC5V0 power bus, leaving
all current available from the 5V regulator to power external circuitry and the USB 5.0V power bus when the Wi-
FIRE is used as a USB Host.
The POWER connector (J5) is used to power shields connected to the Wi-FIRE board. Pin 1 is unconnected, the
following pins are provided on this connector:
 IOREF (pin 2): This pin is tied to the VCC3V3 bus.