Digilent 410-295P-KIT - Manual (Page 18)

ChipKIT Pro MX4 Reference Manual
Copyright Digilent, Inc. All rights reserved.
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Page 18 of 37
• SCK2 JB-04
• SS1 J1-01 (also JD-03)
• SDO1
J1-02 (also JH-08)
• SDI1 J1-03 (also JK-10)
• SCK1 J1-04 (also JD-09)
Detailed information about the operation of the SPI peripherals can be found in the PIC32 Family Reference
Manual, Section 23, Serial Peripheral Interface.
When using the ChipKIT Pro MX4 with the MPIDE and the chipKIT system, the SPI ports are accessed using either
the standard chipKIT SPI library or using the Digilent DSPI library.
The standard SPI library supports access to a single SPI port, SPI2. This is accessed using the SPI object.
The DSPI library supports access to both SPI ports. The DSPI0 object class is used to create an object used to
access the default SPI port, SPI2, connector JB. The DSPI1 object class is used to access SPI1, connector J1.
11 I
2
C ™ Interface
The Inter-Integrated Circuit (I
2
C TM ) Interface provides a medium speed (100K or 400K bps) synchronous serial
communications bus. The I
2
C interface provides master and slave operation using either 7 bit or 10 bit device
addressing. Each device is given a unique address, and the protocol provides the ability to address packets to a
specific device or to broadcast packets to all devices on the bus. Refer to the Microchip PIC32MX3XX/4XX Family
Data Sheet and the PIC32 Family Reference Manual, Section 24, Inter-Integrated Circuit, for detailed information
on configuring and using the I
2
C interface.
The PIC32MX460 microcontroller provides for two independent I
2
C interfaces. The ChipKIT Pro MX4 is designed to
provide dedicated access to one of these interfaces, I2C2, using I
2
C daisy chain connector J6. The other I
2
C
interface, I2C1, is accessed using I
2
C daisy chain connector J2. The signals for I2C1 are shared with Pmod connector
JF, and also appear on pins 1 & 2 of JF.
The I
2
C daisy chain connectors provide two positions for connecting to the I
2
C signals, SDA and SCL, as well as
power and ground. By using two-wire or four-wire MTE cables (available separately from Digilent) a daisy chain of
multiple ChipKIT Pro MX4 boards or other I 2 C-capable boards or devices can be created.
The I
2
C bus is an open-collector bus. Devices on the bus actively drive the signals low. The high state of the I
2
C
signals is achieved by pull-up resistors when no device is driving the lines low. One device on the I
2
C bus must
provide the pull-up resistors. On the ChipKIT Pro MX4, I2C2 has fixed 2.2K ohm pull-up resistors. I2C1 has
selectable pull-up resistors that can be enabled or disabled via jumpers J3 and J4. The pull-ups are enabled by
installing shorting blocks and are disabled by removing the shorting blocks. Generally, only one device on the bus
will have the pull-ups enabled.