DM300019 datasheet(30/50 Pages) MICROCHIP

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dsPICDEM™ 80-Pin Starter Development Board User’s Guide

DS51584B-page 26

The dsPIC DSC device functionality used in this demonstration program includes:

• Setting up I/O ports

• Setting up timer interrupts

• Handling interrupts

To observe this demonstration, close jumper J4 to enable the LEDs, then operate the

switches.

3.3.2

Analog-to-Digital Conversion

To illustrate analog-to-digital conversion, the analog value of potentiometer R13 is

converted by the Analog-to-Digital Converter, ADC12, to a digital value that is

transmitted via UART1 to a PC.

When the HyperTerminal accessory in Microsoft Windows® is connected to the serial

port on the dsPICDEM 80-Pin Starter Development Board, it receives and displays a

stream of three-digit HEX codes that correspond to the 12-bit output value of ADC12.

As the potentiometer R13 is adjusted, the displayed HEX code changes within a range

from 000 to FFF.

The dsPIC30F device functionality used for this demonstration includes:

• Conversion of an analog signal to a 12-bit digital signal

• Conversion of the 12-bit ADC value to HEX and ASCII format

• UART communication handling

To implement this demonstration, connect the J1 connector on the dsPICDEM 80-Pin

Starter Development Board to the RS-232 serial port on the PC with a DB9 cable. Using

the HyperTerminal program available as a Microsoft Windows communications

accessory, configure the serial port to 2400 baud, 8 bits with 1 stop bit, no parity and

no flow control.

3.3.3

Digital-to-Analog Conversion

To illustrate digital-to-analog conversion, the dsPICDEM 80-Pin Starter Development

Board uses the MCP41010 digital potentiometer and MCP6022 Operational Amplifier

(configured as a low-pass filter) to deliver an audio tone to the LINE OUT pin. The

digital input is derived from a table of HEX values in data memory. The demo program

cycles through the table and delivers the selected value to the digital potentiometer via

the Serial Peripheral Interface (SPI) module on the dsPIC DSC device. The table

values cover the full range of the digital potentiometer.

The program communicates a new table value to the digital potentiometer every 125

microseconds, which generates a 400 Hz audio signal out of the low-pass filter.

Switches S1 and S2 are used to change the output frequency to 800 Hz and 1600 Hz,

respectively.

The dsPIC DSC device functionality used for this demonstration includes:

• Mapping of data memory to program memory with PSV addressing

• Initialization of the SPI port

• Loading and transmission of data using hardware SPI

To observe this demonstration, connect an oscilloscope probe to pin 2 of J9 (the LINE

OUT pin).

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