Datasheet

chipKIT™ Wi-FIRE™ Board Reference Manual

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 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 Wi-FIRE 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

Wi-FIRE 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.

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, 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 Wi-FIRE would not

be 5V tolerant. Instead, JP9 was added to allow for the 5V0 bus to the shield to be selectable between 3.3V or

5.0V. If 5.0V is selected, great care must be used to ensure that no input to the PIC32MZ exceeds 3.6V; 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 Wi-FIRE 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 (V

0.4V, V

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 datasheet

available from www.microchip.com.