Digilent chipKIT Uno32 Referenzhandbuch - Seite 10
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device when not using the USB serial
interface. This uses UART1 (U1RX, U1TX) on
the PIC32 microcontroller.
UART port 2: Asynchronous serial port. Pin 39
(RX), Pin 40 (TX). This uses UART2 (U2RX,
U2TX) on the PIC32 microcontroller.
SPI: Synchronous serial port. Pin 10 (SS), Pin
11 (MOSI), Pin 12 (MISO), Pin 13 (SCK). This
uses SPI2 (SS2, SDI2, SDO2, SCK2) on the
PIC32 microcontroller These signals also
appear on connector J8.
Jumpers JP5 and JP7 are used to select
whether the Uno32 operates as a Master
(transmit on MOSI, receive on MISO) or a
Slave (transmit on MISO, receive on MOSI)
device. The shorting blocks on JP5 and JP7
are normally placed in the Master position for
the Uno32 to function as an SPI master.
Jumper JP4 is used to select PWM output or
the SPI SS function on Pin 10. The shorting
block on JP4 should be in the RD4 position to
select PWM output. It should be in the RG9
position to select the SPI SS function.. JP4 will
normally be in the RD4 position. In general, the
only time it needs to be in the RG9 position is
when the Uno32 board is being used as an SPI
slave device.
2
I
C: Synchronous serial interface. The PIC32
microcontroller shares analog pins A4 and A5
2
with the two I
C signals SDA and SCL.
Jumpers JP6 and JP8 are used to select
whether the analog pin functions or the I
functions are being used. The shorting blocks
are placed in the A4/A5 position to select the
analog input function or general digital I/O.
They are placed in the RG3/RG2 position to
2
use the pins for I
C operation. This uses I2C1
(SDA1, SCL1) on the PIC32 microcontroller.
2
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 Uno32 board and must be provided
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externally. The required 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 38 (INT0), Pin 2
(INT1), Pin 7 (INT2), Pin 8 (INT3), Pin 35
(INT4)
User LEDs: Pin 13 (LD4), Pin 43 (LD5). Pin 13
is shared between a connector pin and the
LED. Pin 43 only goes to the LED and not 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 J5. 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. This pin can also be
used as digital pin 42.
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
2
C pin
requires a 32.768Khz frequency source.
Crystal X2 (not loaded), just above and to the
right of the PIC32 microcontroller IC, is
provided for you to solder a 32Khz watch
crystal. The Citizen CFS206-32.768KDZF-UB
crystal can be used in this location.
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, reset of the PIC32
microcontroller can be initiated by the USB
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