Digilent Max32 참조 매뉴얼 - 페이지 9

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Max32™ Board Reference Manual

UART port 2: Asynchronous serial port. Pin 17 (RX2), Pin 16 (TX2). This uses UART3A (U3ARX, U3ATX) on the PIC32

microcontroller.

UART port 3: Asynchronous serial port. Pin 15 (RX3, Pin 14 (TX3). This uses UART3B (U3BRX, U3BTx) on the PIC32

microcontroller.

SPI: Synchronous serial port. Pin 53 (SS), Pin 51 (MOSI), Pin 50 (MISO), Pin 52 (SCK). This uses SPI2A (SS2A, SDI2A,

SDO2A, SCK2A) on the PIC32 microcontroller. These signals also appear on connector J13. Jumpers JP3 and JP4 are

used to select whether the Max32 operates as a Master (transmit on MOSI, receive on MISO) or a Slave (transmit

on MISO, receive on MOSI) device. The shorting blocks on JP3 and JP4 are normally placed in the Master position

for the Max32 to function as an SPI master.

C: Synchronous serial interface. These signals are available on J18 and are shared with pins 21 (SCL) and pin 20

(SDA). This uses I2C1 (SDA1, SCL1) on the PIC32 microcontroller.

Note: The I

C bus uses open collector drivers to allow multiple devices to drive the bus signals. This means that

pull-up resistors must be provided to supply the logic high state for the signals. These pull-up resistors are not on

the Max32 board and must be provided externally. The resistance of the pull-up resistor to use depends on the

total number of devices on the bus, the length of wire, and the clock speed being used. It essentially depends on

distributed capacitance on the bus. The higher the distributed capacitance and the faster the clock speed, the

smaller the resistance should be. Values typically used are in the range of 2K to 10K ohms.

PWM: Pulse width modulated output. Pins 3 (OC1), 5 (OC2), 6 (OC3), 9 (OC4), and 10 (OC5).

External Interrupts: Pin 3 (INT0), Pin 2 (INT1), Pin 7 (INT2), Pin 21 (INT3), Pin 20 (INT4).

User LEDs: Two user LEDs are provided, Pin 13 (LD4) and Pin 86 (LD5). Pin 13 is shared between a connector pin

and LD4. Pin 86 is dedicated to LD5 and is not shared with any connector pin. Driving the pin high turns the LED on,

driving it low turns it off.

A/D Converter Reference: Labeled A, the left-most outer pin on connector J3. This is used to provide an external

voltage reference to determine the input voltage range of the analog pins. The maximum voltage that can be

applied to this pin is 3.3V. Note that this signal is duplicated on connector J8 and corresponds to digital I/O pin 44.

If the A pin is being used as an analog reference, then pin 44 is not useable.

RTCC: real-time clock/calendar. The PIC32 microcontroller contains an RTCC circuit that can be used to maintain

time and date information. The operation of the RTCC requires a 32.768 KHz frequency source. Pin 75 (SOSCI) is

the clock input for the RTCC. A 32.768 KHz oscillator should be connected to this pin to allow use of the RTCC.

RESET: The PIC32 microcontroller is reset by bringing its MCLR pin low. The MCLR pin is connected to the P32_RST

net on the circuit board.

As described earlier, resetting the PIC32 microcontroller can be initiated by the USB serial converter. The USB

serial converter brings the DTR pin low to reset the microcontroller. Jumper JP5 can be used to enable/disable the

ability for the USB serial converter to initiate a reset.

The P32_RST net is connected to pin 1 of power connector J10. This allows circuitry on a shield to reset the

microcontroller, or to ensure that the circuitry on the shield is reset at the same time as the microcontroller.

Connector J13 provides access to the SPI bus. Pin 5 provides access to the SPI Slave Select signal (SS).

On Arduino boards, the corresponding connector is also used as an in-system programming connector as well as

providing access to some of the SPI signals. On Arduino boards, pin 5 of this connector is connected to the reset

net.

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