Datasheet

chipKIT™ WF32™ Board Reference Manual

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GND (pin 6, 7): This provides a common ground connection between the WF32 and the shields. This common

ground is also accessible on connectors J4 and J5.

VEXT (pin 8): This connects to the voltage provided at the external power supply connectors (J14 and J17). This

can be used to provide unregulated input power to the shield. It can also be used to power the WF32 board from

the shield instead of from the external power connector.

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 analog capable I/O pins are not 5V tolerant.

To provide 5V tolerance on those pins, the WF32 contains clamp diodes and current limiting resistors to protect

them from 5V input voltages.

The fact that all I/O pins are 5V tolerant means that it is safe to apply 5V logic levels to any pins on the board

without risk of damaging the PIC32 microcontroller.

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 WF32 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 25mA on all digital I/O pins. However, to keep the

output voltage within the specified output voltage range (V

0.4V, V

2.4V) the pin current must be restricted to

+7/-12mA. The maximum current that can be sourced or sunk across all I/O pins simultaneously is +/-200mA. The

maximum voltage that can be applied to any I/O pin is 5.5V although not all pins are 5V tolerant. For more detailed

specifications, refer to the PIC32MX5XX/6XX/7XX Data Sheet available from www.microchip.com.

Note that the series resistors that are part of the voltage clamp circuit to provide 5V tolerance on the analog

capable I/O pins, limiting the current that can be sourced or sunk by those pins. These resistors add 200 ohms of

resistance to the input/output circuit and limit the effective drive current to about 1mA-2mA source/sink capability

on the analog capable pins.

Connectors J7 and J9 are 2x8 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.

Connector J8 is a 2x6 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.