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chipKIT™ MX3 Board Reference Manual
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Pins 0-7 are on connector JA, pins 8-15 on JB, pins 16-23 on JC, pins 24-31 on JD, and pins 32-39 on JE. Refer to the
tables in Appendices B–D for detailed information about the pin mapping between Pmod connector, logical pin
number, and PIC32 microcontroller pin number and pin function.
When using the chipKIT MX3 with the MPIDE the functions pinMode(), digitalRead(), and digitalWrite() are used for
digital pin I/O.
The pinMode() function is used to set the pin direction. Pin direction can be set to: INPUT, OUTPUT, or OPEN.
OPEN is used for open-drain and implies output.
The digitalRead() and digitalWrite() functions are used to read or write the pins. DigitalRead() returns the current
state of the specified pin, and digitalWrite is used to set the state of an output pin. The pin state can be either
HIGH or LOW.
4.1 User LEDs
Two LEDs are provided, LD4 and LD5, connected to I/O port F bits 0 and 1 (RF00 and RF01). LATF Bit 0 is connected
to LD4 and bit 1 is connected to LD5. The LEDs are turned on or off by configuring these two pins as outputs and
driving them high or low. Driving the pin high turns the LED on, driving it low turns it off. These I/O pins are
dedicated to use with the LEDs and are not available at any connector.
When using the MPIDE and the chipKIT system, the LEDs are accessed as digital pins 42 (LD4) and 43 (LD5), or
preferably, using the symbols PIN_LED1 and PIN_LED2.
4.2 5V Signal Compatibility
The PIC32 microcontroller operates at 3.3V. And the I/O pins provide 3.3V logic levels. It is possible, in some
circumstances, to use the chipKIT MX3 to operate with 5V logic devices.
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. It is safe to apply 5V logic signals directly to these
pins without risk of damage to the microcontroller.
The analog capable I/O pins on the PIC32 are not 5V tolerant. The absolute maximum voltage rating for the analog
pins is 3.6V. Generally, the analog pins are the pins on I/O port B, however, there are other non-5V tolerant pins on
the device.
Refer to the PIC32MX3XX/4XX Family Data Sheet for more information about which pins on the device are 5V
tolerant before applying input signals higher than 3.3V to any pin on the chipKIT MX3 board.
If a 5V signal is applied to a non-5V tolerant pin, some external means must be used to limit the applied voltage to
3.6V or less. The chipKIT MX3 board provides 200 ohm series resistors between the microcontroller pins and the
Pmod connector pins. These resistors are primarily intended to provide short circuit protection on the outputs, but
will also provide limited protection if a 5V signal is inadvertently applied to a non-5V tolerant pin.