Microchip Technology dsPIC DSC DTMF, Руководство пользователя

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©
2008 Microchip Technology Inc. DS70332A-page 23
dsPIC
®
DSC DTMF DETECTION
LIBRARY USER’S GUIDE
Chapter 4. DTMF Detection Demonstration
This chapter analyzes a sample application program that demonstrates the key
functionality of the dsPIC DSC DTMF Detection Library. This sample demonstration
offers hands-on exposure to the library and provides an informal way to gain
implementation experience.
The sample program demonstrates the DTMF tone detection over a dial-up phone line.
The program is built using MPLAB IDE and MPLAB ICD 2, and is loaded into a
dsPIC33F device. The dsPICDEM.net Connectivity Board is used to execute the
demonstration program. Topic covered includes:
• Setting Up the dsPICDEM.net Board
• DTMF PSTN Phone Line Demonstration
4.1 SETTING UP THE dsPICDEM.net BOARD
Use the following procedures to set up the board:
1. Make sure the 2X2 shunts on J17 and J19 jumpers are inserted in a manner that
ensures vertical alignment and are perpendicular to the LCD display.
2. To apply power to the dsPICDEM.net board, remove the J6 jumper and apply
3.3V to J6 terminal.
3. Do not connect the 9V DC power supply to J14 terminal.
4. Jumper M0 must be kept open.
5. Set up the HyperTerminal connection as follows:
• Bits per second: 19200
• Data bits: 8 bits
• Parity: None
• Stop bits: 1 Stop bit
• Flow Control: Hardware Flow Control
4.2 DTMF PSTN PHONE LINE DEMONSTRATION
In this demonstration setup, the dsPIC DSC DTMF Detection Library interacts with a
remote telephone over the PSTN, as illustrated in Figure 4-1. The telephone handset
is used to dial the dsPICDEM.net board over an analog phone line. The Si3034/Si3035
DAA/AFE interface on the board detects the ring and alerts the dsPIC33FJ256GP710
device, which then executes the DTMF detection algorithm. When the off-hook function
is simulated by pressing the S1 switch, the remote telephone communicates with the
dsPIC DSC DTMF Detection Library via the DAA/AFE modem circuitry.
Digits can now be generated from the telephone keypad and recognized by the DTMF
detection algorithm. The recognized digits are sent to the UART for display. The UART
passes the digits to the attached PC running the HyperTerminal.