Digilent MX4cK - Manual (Page 18)

Cerebot MX4cK Reference Manual
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• J2-3 – SDA1
• J2-4 – SDA1
• J2-5 – GND
• J2-6 – GND
• J2-7 – BRD_3V3
• J2-8 – BRD_3V3
Connector J6, I2C2
• J6-1 – SCL2
• J6-2 – SCL2
• J6-3 – SDA2
• J6-4 – SDA2
• J6-5 – GND
• J6-6 – GND
• J6-7 – BRD_3V3
• J6-8 – BRD_3V3
On-Board I
2
C Peripheral Devices
The Cerebot MX4cK provides two on-board I
2 C
peripheral devices, a Microchip 24LC256 serial
EEPROM, and a Microchip MCP4725 Digital to
Analog Converter. These devices are both
connected to I2C2. The 24LC256 is a 256Kbit
(32Kbyte) serial EEPROM device to provide
non-volatile memory storage. The MCP4725 is
a single channel, 12-bit, serial digital to analog
converter that provides an analog output
voltage for various uses. The device address
for IC2, the 24LC256 is 1010000 (0x50). The
device address for IC3, the MCP4725, is
1100000 (0x60).
Refer to the Microchip data sheets for detailed
information on the operation of these devices.
The analog output voltage from IC3 is available
at two places on the Cerebot MX4cK board.
The two pin header, J10, provides the DAC
output voltage and ground for connection to
off-board applications.
The DAC output signal is also available at the
center, DAC, position of jumper block J16.
Placing a shorting block at this position
connects the DAC output to pin 20 on the
PIC32MX460 microcontroller. One of the
functions for this pin is as one of the inputs to
analog comparator #1 on the PIC32 device.
This allows the output of the DAC to be used
as a programmable reference voltage for the
comparator.
Analog Inputs
The PIC32MX460 microcontroller provides a
10-bit analog to digital (A/D) converter that
provides up to sixteen analog inputs. The
Cerebot MX4cK board provides access to 14
of them on the Pmod connectors. The
converted values produced by the A/D
converter will be in the range 0–1023.
For detailed information on the operation and
use of the A/D converter, refer to the PIC32
Family Reference Manual, Section 17, 10-bit
AD Converter.
The analog inputs are accessed using the
analogRead() function in the chipKIT MPIDE
software. The analog input pin number is
specified using the symbols A0–A13. The
digital pin numbers for the pin or the numbers
0–13 can also be used, but using the symbols
A0–A13 is recommended.
The following gives the Pmod connector
position, digital pin number, and
microcontroller I/O port and bit number for the
analog inputs:
• A0 – JJ-01, digital pin 56, RB0
• A1 – JJ-02, digital pin 57, RB1
• A2 – JJ-03, digital pin 58, RB2
• A3 – JJ-04, digital pin 59, RB3
• A4 – JJ-07, digital pin 60, RB4
• A5 – JJ-08, digital pin 61, RB5
• A6 – JJ-09, digital pin 62, RB8
• A7 – JJ-10, digital pin 63, RB9
• A8 – JK-01, digital pin 64, RB10
• A9 – JK-02, digital pin 65, RB11
• A10 – JK-03, digital pin 66, RB12
• A11 – JK-04, digital pin 67, RB13