Transcript MICROCONTROLLER BASED TELECOM SWITCH

MICROCONTROLLER BASED
TELECOM SWITCH
SPONSORED BY: ARJ ASIA
External Guide: Mr. Jitendra Date
Internal Guide: Mr. M.B. Tirmare
By: Neha Purandare
Janhavi Shah
Sonali Shelke
PROBLEM:
A "telephone solicitation" is a telephone call that acts as an
advertisement. Even if you have an unlisted, non-listed, or non-published
telephone number, you may still receive unsolicited telephone calls with
automated or prerecorded messages. In some cases unlisted or nonlisted numbers can be obtained from a directory assistance operator. They,
along with non-published numbers, may be sold to other organizations or
people with whom you have done business. Some sales organizations call
all numbers in numerical order for a neighborhood or area.
SOLUTION:
In the field of telecommunications, a telephone exchange (US:
telephone switch) is a piece of equipment that connects phone calls. It is
what makes your phone calls "work" in the sense of making connections and
relaying the speech information. Here we are using our telecom switch to
connect only the right call and block the unwanted ones.
BLOCK DIAGRAM
EXPLANATION OF BLOCK DIAGRAM
DTMF Encoder:
The DTMF encoder resembles the telephone
set. It uses DTMF encoder integrated circuit, Chip UM
91214B . This IC produces DTMF signals.
DTMF Decoder:
It consists of MT8870D chip which is a
direct DTMF detector. Its output is a 4- bit BCD code;
each 4 bit code corresponding to a DTMF tone pair.
Whenever a valid tone pair is detected at the input,
the StD pin goes high indicating that the tone pair has
been latched.
• Microcontroller:
PIC18F452 accepts the 4 bit BCD code from
MT8870D and checks if the DTMF tone pair stands for
numbers between 0 to 9. If it does, it is considered a
valid no. and the user is allowed to receive the call; else
it is routed to voice chip and rejected.
ISD2560 Voice chip:
If the call is unsolicited one, the P/R bar pin of this
chip is pulled to Vcc and a message rejecting the call is
played back to the caller. The message is pre-recorded on
the chip by manual switching of P/R bar and CE bar pins.
Features of PIC18F452
• 16-bit wide instructions, 8-bit wide data path
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Linear program memory addressing to 32 Kbytes
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Linear data memory addressing to 1.5 Kbytes
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100,000 erase/write cycle Enhanced FLASH program
memory typical
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1,000,000 erase/write cycle Data EEPROM memory.
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Low power, high speed FLASH/EEPROM technology.
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Wide operating voltage range (2.0V to 5.5V)
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Watchdog Timer (WDT) with its own On-Chip RC
oscillator for reliable operation.
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Programmable code protection
Features of MT8870D
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DTMF Receiver
Low power consumption
Internal gain setting amplifier
Adjustable guard time
Central office quality
Power-down mode
Inhibit mode
FEATURES OF ISD2560
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Easy to use, voice
record/playback solution.
Single chip with 60 sec duration
Manual switch or uC compatible.
Auto power-down (push-button)
mode
Can handle multiple messages
On-chip clock source
Single +5 volt power supply
FLOWCHART
START
ACCEPT INPUT
TONES FROM
MT8870D
IS
StD=1?
Y
A
N
A
IS
TONE
BET 0
TO 9?
Y
MAKE
RD1 = 1
STOP
N
MAKE
RD0 = 1
SOFTWARE
• Development Environment:
The MPLAB C18 Code Development Systems are complete
ANSI ‘C’ compilers for Microchip’s PIC18CXXX family of
microcontrollers. This compiler provide powerful integration
capabilities and ease of use not found with other compilers.
• Programmer: PICSTART Plus Entry Level Development
Programmer
The PICSTART Plus development programmer is an easyto-use, low cost, prototype programmer. It connects to the PC via a
COM (RS-232) port. MPLAB
Integrated Development Environment software makes using the
programmer simple and efficient. The PICSTART Plus development
programmer supports all PICmicro devices with up to 40 pins.