Digilent MX4cK Manual do Utilizador descarregar pdf (Página 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

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