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1MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Chapter-1
INTRODUCTION
The main objective of our project is to generate different
tunes having different frequencies using an advanced micro controller family. So we have
selected 16F877A PIC for this purpose to achieve our requirements. It includes keyboard
having 8 micro switches, frequency synthesizer, a low wattage audio power amplifier and
a 10 watt speaker. All these sections are controlled by a micro controller namely
16F877A. Power requirements for all these sections are controlled by a five volt and nine
volt regulated ICs namely LM7805 and LM7809.
The input micro key depressions are monitored at every
instant by micro controller , based on stored programs written in assembly language that
are stored in internal flash of PIC. The program consists of key depression monitoring,
activation and deactivation of play back and recording. First four keys of the keyboard are
meant for recording and the rest for playback. When a key is pressed the micro controller
receives a high signal through its port. Activation signals are produced which govern the
APR9600 chip. In respond to the signal the APR9600 either records a message or plays a
message. It produces a message signal of 60 seconds, 40 seconds and 32 seconds duration
according to the oscillation frequency selected by the user. It has the feature of selecting 8
messages of fixed duration depending on data bits of message select pin. A condenser
microphone is used for recording the required message. The generated message having
very low wattage activates a loud speaker. In this project we are using an audio power
amplifier for further amplification of the generated APR frequencies. The amplifier is a
dual channel power amplifier based on UTC6283 IC. This IC is commonly used in inbuilt
digital audio systems. The amplified output is given to a speaker which produces the
required acoustic signals.
Dept of ECE Govt. Engg. College, Sreekrishnapuram
2MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Chapter-2
BLOCK DIAGRAM AND DESCRIPTION
2.1 BLOCK DIAGRAM
Dept of ECE Govt. Engg. College, Sreekrishnapuram
KEY BOAR
D
PIC MICRO CONTR-OLLER
FREQU-
ENCY SYNTHESIZ
ER
SPEAKER
5VOLT POWE
R SUPPL
Y
DUAL
AUDIO
POWER
AMPLIF-IER
9VOLT POWE
R SUPPL
Y
MIC
3MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
2.2 BLOCK DIAGRAM DESCRIPTION
2.2.1 MIC
A condenser MIC is used. The condenser MIC converts acoustic
signals into electrical signals. The condenser MIC is connected to the frequency
synthesizer so that acoustic signals can be recorded.
2.2.2 POWER SUPPLY
We used two voltage levels here i.e. +5 V & +9 V. +5 V power
supply is fed to PIC and frequency synthesizer. +9 V power supply is fed to dual
audio power amplifier.
2.2.3 SWITCH ARRAY
Switch array contains eight switches, four switches for play back
and remaining for recording. For play back a high to low transition is needed and
for recording a continuous low is needed.
2.2.4 PIC MICRO CONTROLLER
In this Peripheral Interface Controller (PIC) IC, PORT B is
selected as input ports and PORT C as output ports. We used PIC 16F877A, which
has got EPROM, RAM and a FLASH memory of 8K. The depression produced by
the key is monitored by this PIC. Its output is fed to the input of the frequency
synthesizer. PIC 16F877A is a 40 pin IC, and have a clock frequency of 20MHz.
The program for this PIC is done in assembly language. Instead of general purpose
registers in micro processors, there are working register W in PIC and also has
user-defined registers.
2.2.5 VOICE RECORDING AND PLAYBACK
We use an IC named APR9600 which has 28 pins as a high quality
voice recording and playback solution. It also has storage capacity. It can store
almost eight messages and can store messages of maximum sixty second duration.
Dept of ECE Govt. Engg. College, Sreekrishnapuram
4MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
2.2.6 POWER AMPLIFER
Dual channel power amplifier based on the UTC 6283 is used in
this. This is commonly used in inbuilt digital audio systems. It amplifies the output
from APR 9600.
2.2.7 SPEAKER
It is a simple speaker which converts the electrical signals into
acoustic signals.
Dept of ECE Govt. Engg. College, Sreekrishnapuram
5MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Chapter-3
CIRCUIT DIAGRAM & EXPLANATION
3.1 POWER SUPPLY SECTION
Figure 3.1 FIVE VOLT REGULATED POWER SUPPLY
Power supply section contains three sections i.e. rectifier section, filter
section, voltage regulator section to produce +5 V from 9 V / 1 A transformer. In regulator
section two capacitors of 0.1 µF can be used to maintain the spikes during the voltage
variation. LM-7805 is used as voltage regulator IC. This +5 V is fed to PIC and APR
9600. A +9 V supply is fed to the dual audio power amplifier.
3.2 PIC MICRO CONTROLLER SECTION
Keyboard containing eight switches in which four switches for play back
and remaining for recording is interfaced with PIC 16F877A microcontroller IC having 8
K flash memory. In that PORT B is set as input port. PORT B is set as input, and PORT C
as output port. PORT B has got internal pull up resistors which are normally at +5 V
MCLR/VPP (32nd pin) is meant for memory clear and VPP will get directly from burner
kit.
Dept of ECE Govt. Engg. College, Sreekrishnapuram
6
RESET
1 KΩ1 KΩ
1 KΩ
+ 5 V
22 p F
22 p F 20 MHz
MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Figure 3.2 PIC- KEYBOARD INTERFACE
In this mini- project we made use of PIC 16F877A there are only 35 single word
instruction to learn in microcontroller. It is a 40 pin IC the data memory is partitioned in to
multiple banks which contain the general purpose registers and the special function
registers. Bits RP1 and RP0 are the bank select bits.
TABLE 3.2 BANK SELECTING
RP1:RP0 BANK
00 0
01 1
10 2
11 3
Thus there are four banks; each extends up to 128 bytes. All implemented
banks contain special function registers. All banks contain status registers contain the
arithmetic status of the ALU, the RESET status and the bank select bits for the data
memory.
PIC contains five PORTS, i.e. PORT A (6 bit), PORT B (8 bit), PORT C
(8 bit), PORT D (8 bit) and PORT E (3 bit) which are confined to BANK0. The
Dept of ECE Govt. Engg. College, Sreekrishnapuram
To APR 9600
7MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
corresponding data direction registers TRIS A, TRIS B, TRIS C, TRIS D and TRIS E are
confined to BANK1. Clearing this data direction register will make corresponding port pin
as output.
Here we made PORT B as input by setting its corresponding bits to 1 and
PORT C as output by clearing corresponding bits. PORT B has got internal pull up
resistors which are normally at + 5 V.
When a key is pressed, the corresponding key depression is monitored by
the PIC. Accordingly an output is generated after executing the program and output is
generated in PORT C. The 27th pin in APR9600 IC is connected to a manual switch by
which we can control the record-playback mode.
In recording mode, we have to press recording switch continuously, the
corresponding PORT C bit is pulled to low and it remains in low state as long as we press
the switch. This continuous low output is fed to next stage which leads to recording.
In playback mode, we have to disconnect the 27th pin of APR9600 IC
from ground. This enables the playback switches and disables the recording switches.
Through programming, we have made the pull up resistors disabled.
Hence RB’s are in zero state. When key is pressed, corresponding PORTB bit becomes 1,
hence it outs a low and is fed to the input of the APR9600 IC. Then the current will sink to
PORT C bit in APR9600 which causes a high to low transition in APR9600. Thus
recorded message is played.
3.3 FREQUENCY SYNTHESIZER SECTION
APR9600 is used as a high quality voice recording and playback solution.
User selectable messaging options one present in this IC. Level activated recording and
edge activated play back switches makes its operation easy. It has got low power
consumption and a play back capability of 40 – 60 seconds. The device supports both
random and sequential access of multiple messages
Dept of ECE Govt. Engg. College, Sreekrishnapuram
8MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Figure 3.3 VOICE RECORDING/PLAYBACK USING APR9600
The amplified microphone signal is fed into the device by connecting the
Ana-out pin to the Ana-In pin through in external dc block capacitor. Recording can be fed
directly into the Ana-in pin through a dc blocking capacitor. However the connection
between Ana-In and Ana-out is still required for playback. When playback is desire the
previously stored recording is retrieved from memory, low pass filtered and amplified for
playback.
Random access mode supports two, four or eight messages segments of
fixed duration. Sequential access mode messages sequentially. We used sequential mode
access in this. APR has an internal memory of 256 k.
3.3.1 Function Description of Playback in Tape Mode
On power-up, the device is ready to record or play back, starting at
the first address in the memory array. Before you can begin playback, the /CE
input must be set to low to enable the device and /RE must be set to high to disable
recording and enable playback. The first high to low going pulse of the
/M1_Message pin initiates playback from the beginning of the current message; on
Dept of ECE Govt. Engg. College, Sreekrishnapuram
9MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
power up the first message is the current message. When the /M1_Message pin
pulses low the second time, playback of the current message stops immediately.
When the /M1_Message pin pulses low a third time, playback of the current
message starts again from its beginning. If you hold the /M1_Message pin low
continuously the same message will play continuously in a looping fashion. A
1,530 ms period of silence is inserted during looping as an indicator to the user of
the transition between the beginning and end of the message.
Note that in auto rewind mode the device always rewinds to the
beginning of the current message. To listen to a subsequent message the device
must be fast forwarded past the current message to the next message. This function
is accomplished by toggling the /M2_Next pin from high to low. The pulse must
be low for least 400 cycles of the sampling clock. After the device is incremented
to the desired message the user can initiate playback of the message with the
playback sequence described above. A special case exists when the /M2_Next pin
goes low during playback. Playback of the current message will stop, the device
will beep, advance to the next message and initiate playback of the next message.
(Note that if /M2_Next goes low when not in playback mode, the device will
prepare to play the next message, but will not actually initiate playback). If the /CE
pin goes low during playback, playback of the current message will stop, the
device will beep, reset to the beginning of the first message, and wait for a
subsequent playback command. When you reach the end of the memory array, any
subsequent pulsing of /M1_Message or /M2_Next will only result in a double
beep. To proceed from this state the user must rewind the device to the beginning
of the memory array. This can be accomplished by toggling the /CE pin low or
cycling power.
If the 27th pin /RE is grounded it refers to record mode, and if that
is connected to the VCC, then play back mode. It can store up to eight messages
corresponding to configuration of message select pins MSEL1(24 th pin) and
MSEL2 (25th pin).
Dept of ECE Govt. Engg. College, Sreekrishnapuram
10MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
TABLE 3.3.1 MESSAGE SELECTON
MSEL1 MSEL2 Output
0 0 Only one message for
record/play back
0 1 2
1 0 4
1 1 8
For 8 messages, M8 must be disconnected from ground. We set
MSEL1 and MSEL2 as 0, hence 4 message outputs. An internal oscillator provides
the APR 9600 sampling clock.
Oscillator frequency can be changed by changing the resistance
from the OscR pin to GND. Table 4.3.2 summarizes resistance values and the
corresponding sampling frequencies, as well as the resulting input bandwidth and
duration.
TABLE 3.3.2 REFERENCE ROSC VALUE & SAMPLING FREQUENCY
Ref Rosc SamplingFrequency
Input Bandwidth Duration
84K 4.2KHz 2.1KHz 60sec
38K 6.4KHz 3.2KHz 40sec
24K 8.0KHz 4.0KHz 32sec
More simply and clearly, the PORT C outputs of PIC IC is fed to
input line M1-M8 of APR IC. In recording mode, /RE pin has to be grounded
which enables the recording keys in the switch arrays. PIC’s continuous low output
is fed into the APR’s in-out lines which are normally at high state. At that time
current will sink from that corresponding PORT C bit. Thus corresponding input
bits of the APR is pulled to low allowing recording a message.
In playback mode we have to disconnect the 27th pin of APR IC
from ground which enables the playback switch has a corresponding fixed memory
slot in the APR IC where the recording messages are stored. When playback
switch is pressed, the corresponding PORT C bit will out zero which is fed to the
APR input, current will sink to the PORT C producing a high low transition
causing playback of recorded messages.
Dept of ECE Govt. Engg. College, Sreekrishnapuram
11MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
3.4 POWER AMPLIFIER SECTION
We used UTC 6283 dual channel audio amplifier in the amplifier section.
It contains internally two Operational Amplifiers since it’s a low voltage amplifier. It is
used as inbuilt amplifier in CD Players and DVD Players. The output of amplifiers is
connected to the 10 W speaker it can be connected to speakers having further more
wattage.
The output from APR 9600 is amplified by this dual channel amplifier.
It’s important to note that the output is mono.
Figure 3.4 POWER AMPLIFIER
Chapter-4
Dept of ECE Govt. Engg. College, Sreekrishnapuram
12MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
SOFTWARE SECTION
;starting play/rec activation program in asm
;header file declaration of processor 16F877A
************************************************************************
******
LIST P = 16F877A
#include "P16F877A.inc"
************************************************************************
***********
;declare temporary registers from addrr:20H
************************************************************************
***********
cblock h'20'
counta
endc
org 0*00
************************************************************************
*****
;intialisation of PORTS…….
;PORTB for key inputs…..
;PORTC for output
************************************************************************
******
bsf STATUS,RP0
movlw b'11111111'
movwf TRISB
movlw b'00000000'
movwf TRISC
bcf STATUS,RP0
LOOP : clrf PORTB
Dept of ECE Govt. Engg. College, Sreekrishnapuram
13MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
************************************************************************
*********
;disable pull up in PORTB
************************************************************************
********
banksel OPTION_REG
movlw 0*80
movwf OPTION_REG
************************************************************************
*************
;start checking of key status
************************************************************************
*********
banksel PORTB
movlw h'01'
xorlw PORTB
btfsc STATUS,Z
call PLAY_MESSG1
movlw h'02'
xorlw PORTB
btfsc STATUS,Z
call PLAY_MESSG2
movlw h'04'
xorlw PORTB
btfsc STATUS,Z
call PLAY_MESSG3
movlw h'08'
xorlw PORTB
btfsc STATUS,Z
call PLAY_MESSG4
movlw h'10'
xorlw PORTB
btfsc STATUS,Z
call REC_MESSG1
Dept of ECE Govt. Engg. College, Sreekrishnapuram
14MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
movlw h'20'
xorlw PORTB
btfsc STATUS,Z
call REC_MESSG2
movlw h'40'
xorlw PORTB
btfsc STATUS,Z
call REC_MESSG3
movlw h'80'
xorlw PORTB
btfsc STATUS,Z
call REC_MESSG4
goto LOOP
PLAY_MESSG1
Banksel PORTC
Movlw 0*FF
Movwf PORTC
Call DELAY_TRANS
Movlw h’FE’
movwf PORTC
return
PLAY_MESSG2
Banksel PORTC
Movlw 0*FF
Movwf PORTC
Call DELAY_TRANS
Movlw h’FD’
movwf PORTC
return
PLAY_MESSG3
Banksel PORTC
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15MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Movlw 0*FF
Movwf PORTC
Call DELAY_TRANS
Movlw h’FB’
movwf PORTC
return
PLAY_MESSG4
Banksel PORTC
Movlw 0*FF
Movwf PORTC
Call DELAY_TRANS
Movlw h’F7’
movwf PORTC
return
REC_MESSG1
Movlw 0*FE
Movwf PORTC
Return
REC_MESSG2
Movlw 0*FD
Movwf PORTC
return
REC_MESSG3
Movlw 0*FB
Movwf PORTC
return
REC_MESSG4
Movlw 0*F7
Movwf PORTC
Return
************************************************************************
*****************
;delay for playback transition
Dept of ECE Govt. Engg. College, Sreekrishnapuram
16MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
************************************************************************
**************
DELAY_TRANS
Movlw 0*ff
Movwf counta
Decfsz counta,f
Goto$-1
Return
end
;end of the play/rec activation program
Dept of ECE Govt. Engg. College, Sreekrishnapuram
17MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Chapter-5
APPLICATIONS AND FUTURE SCOPE
5.1 APPLICATIONS
5.1.1 Voice aid
If the stored messages are sounds of alphabets, those who are deaf
and blind can communicate to others.
5.1.2 Electronic organs
If the stored messages are tones of musical notes, it can be used as
a simple micro controller based musical instrument containing 8 notes.
5.1.3 Voice recorder
By arranging it in record mode, we can record any voice given to
the input of a Mic. The play back of the recorded messages is obtained by
changing the mode to play back mode.
5.2 FUTURE SCOPE
5.2.1 Security system
If this product is interfaced with micro controller kit by setting
reference sounds, then the playback sound will be compared with the reference
sounds. If these two sounds are equal, the corresponding will be available to that
user. In locker system, laptop systems this type of security system may find a good
scope. If it is connected to DSP kit, then frequencies are compared with the
reference frequency and desired is selected from the input.
5.2.2 Voice comparison
By setting a reference voice, any voice given to the Mic input of
our product can be compared.
Chapter-6
Dept of ECE Govt. Engg. College, Sreekrishnapuram
18MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
ADVANTAGES AND DISADVANTAGES
6.1 ADVANTAGES
No other recording system is required
As it has inbuilt memory of 256 K, no other recording and storage system
is required.
Cheap
All the components in this record and play back system is very cheap and
easily available
Programming and development systems are not required for the frequency
synthesizer separately
Low power consumption
Minimum external components are required
6.2 DISADVANTAGES
Time limitation
The maximum message duration capacity of this product is limited to 60
seconds. It doesn’t have any applications in projects requiring more
duration.
Message limitation
This product can handle at most 8 messages by changing the configuration
of message select pins APR9600. if more number of messages are
required , it will fail.
Introduction of distortion
APR eliminates the need for encoding and compression. This property
introduces distortions in the circuit.
Chapter-7
Dept of ECE Govt. Engg. College, Sreekrishnapuram
19MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
CONCLUSION AND RESULT
Features of ICs PIC16F877A, APR9600 and UTC6283 are studied.
Assembly language program for our product is analyzed and implemented to
PIC IC using MPLAB software.
All parts are combined and obtained our desired product.
Figure 7.1 INTERNAL PICTURE OF THE FINAL PRODUCT
Dept of ECE Govt. Engg. College, Sreekrishnapuram
20MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Figure 7.2 EXTERNAL PICTURE OF THE FINAL PRODUCT
Figure 7.3 OUTPUT WAVEFORM FROM THE AMPLIFIER
Dept of ECE Govt. Engg. College, Sreekrishnapuram
21MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Chapter-8
REFERENCES
www.electronicsforyou.com
www.google.com
www.wikipedia.com
www.hobbyprojects.com
Dept of ECE Govt. Engg. College, Sreekrishnapuram
22MICRO CONTROLLER BASED AUDIO RECORDING/PLAYBACK SYSTEM
Chapter-9
APPENDIX
Dept of ECE Govt. Engg. College, Sreekrishnapuram
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