MICROPROCESSORS AND MICROCONTROLLER 1

Transcription

1 MICROPROCESSORS AND MICROCONTROLLER 1 Microprocessor Applications Data Acquisition System Data acquisition is the process of sampling signals that measure real world physical conditions ( such as temperature, voltage, pressure, sound, etc..) and converting the resulting samples into digital numeric values that can be manipulated by a microprocessor/microcontroller/computer. Data acquisition systems (DAS or DAQ) typically convert analog information to digital values for processing. The components of data acquisition systems include: Sensors - to convert physical parameters to electrical signals. Signal conditioning circuitry - to convert sensor signals into a form that can be converted to digital values. Sample and Hold circuits to hold analog input value over a certain length of time for subsequent processing. Analog-to-digital converters - to convert conditioned sensor signals to digital values. Analog Multiplexors To measure or quantize more than one signal A basic DAQ system consists of sensors, DAQ measurement hardware, and a microprocessor / microcontroller/computer with programmable software. Keyboard Process Transducers Analog Mux Sample / Hold Amp A/ D µp/µc Block Diagram of DAS Display K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 1

2 MICROPROCESSORS AND MICROCONTROLLER 2 Sample and Hold Circuit (S/H) If an attempt is made to digitize a rapidly changing input signal, the input signal would have changed before the conversion is complete. The output of the converter will represent the input at the end of the conversion cycle rather than at the start. Therefore an error ΔV is introduced in the output voltage. This error voltage is a function of the rate of change of the input signal. This error is eliminated by using a sample and hold with a buffer amplifier on the input of the A/D converter. The function of the S/H circuit is to sample an analog input signal and hold this value over a certain length of time for subsequent processing. (i.e.) S/H circuit is used to maintain a stable input to the ADC during conversion. A S/H amplifier has two modes of operation controlled by a digital signal. In the SAMPLE mode the output follows the input, normally with unity gain. In the HOLD mode, the output of the S/H amplifier retains the last value it had until it switches to sample mode. LF 398A S/H. The LF398A is a 8 pin DIP ( National semiconductor). The only component to be externally connected is the hold capacitor. A low value of capacitance is preferred for quick charging by the input amplifier and a high capacitance is preferred to retain the charge for a longer duration. In a particular application, proper capacitance value should be selected for optimum performance. Parameters of S/H Acquisition time: This is the time required by the output of the device to reach its final value within a specified error percentage in the Sample Mode. Aperture time: It is the time required to switch from sample state to hold state. Typical value of aperture time is 10 ms. K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 2

3 MICROPROCESSORS AND MICROCONTROLLER 3 Droop: It is the change of output voltage per unit time during hold, as a result of leakage or bias currents flowing through the capacitor. For LF398A the droop value is 5mV/min. Fig. Multiplexers Multiplexers are basically switches to transfer the signals from one of the input sources to the output on the control command. The control command should clearly identify the input source from which the information signals is to be transferred. The various input sources are called multiplexer channels. The information required to select the channel is known as address of the channel. The analog switches used in the multiplexer may be any one of several types of electromechanical or solid state switches. Interfacing 7 segment displays Decimal digits and some letters of the alphabet can be displayed using a seven segment display devices. In seven segment displays an LED is used for each segment. There are two types of seven-segment display devices: Common Anode and Common Cathode types. K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 3

4 MICROPROCESSORS AND MICROCONTROLLER 4 In common anode type all of the anodes of the LEDs are connected in common; in the common cathode type all of the cathodes of the LEDs are connected in common. These variations require different drive arrangements. BCD to seven segment (7447 / 7448) decoder drivers are available for driving seven segment displays.7447 is used to drive common anode type and 7448 is used to drive common cathode type. The following figure shows the connection diagrams. K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 4

5 MICROPROCESSORS AND MICROCONTROLLER 5 In common anode type, logic 0 at decoder driver output turns a segment ON where as in common cathodes type a logic 1 at decoder driver output turns a segment ON. Interfacing 7 segment displays with 8085 D0-D PPI PA0-PA RD 8085 WR A0-A7 ADDRESS DECODER CS PA4-PA IO/M Here the output device 7-segment displays are interfaced with 8085 in I/O mapped IO scheme. Using a suitable decoder circuit the address of the ports of 8255 can be fixed. Here Port A is configured as an output port. Pins PA0-PA3 is used to send the BCD value of the LSD and PA4-PA7 is used to send the BCD value of MSD. Using this scheme it is possible to displays numerical values from 00 to 99. The following program demonstrates the working of the above circuit. Aim: To display the content of the memory location 4500H in the seven segment display device. Control word formation: Port A, Port B, Port C : output Mode: Simple I/O Control Word: 80H K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 5

6 MICROPROCESSORS AND MICROCONTROLLER 6 Program: To display two digits on a 7 segment displays START: MVI A, 80 ; Control word 80H is stored in Acc OUT CWR ; Control word is send to Control Word Reg. of 8255 LDA 4500 ; The data to be displayed is loaded in to Acc DAA ; Decimal Adjust Accumulator to get the BCD values OUT PORTA ; PA0-PA3 receives the BCD value of LSD and HLT ; PA4-PA7 receives the BCD value of MSD. ;The corresponding digits are displayed in the 7-seg.disp. DIGITAL CLOCK A digital clock is a type of clock that displays the time digitally i.e. in numerals as opposed to an analog clock. Also many microprocessor applications would require, doing certain tasks at specific time of the day or would involve the time of day in some other form. For example switching ON and OFF street lights at specific time in the evening and following morning or punching entry time of every worker for a shift, at a factory gate etc. A basic requirement of these types of applications is a real time digital clock with a display of current time. A digital clock can be implemented by using a dedicated hardware like MM5314 or by software. The following program is used to implement a digital clock on an 8085 system. The basic requirement of a digital clock is the seven segment displays to show Hours, Minutes & Seconds. The seven segment displays are interfaced with the 8085 processor through the ports of 8255 PPI available in the microprocessor trainer Kit. The displays are driven by suitable seven segment decoder driver (7447/7448). The main part of the digital clock program is the accurate generation of 1 Hz frequency or 1 second time delay for reference. K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 6

7 MICROPROCESSORS AND MICROCONTROLLER 7 The 1Hz frequency or 1 second time delay can be produced exactly by using a timer 8253 or by using a well designed delay subroutine. Program Logic Three CPU registers are used to count Hours, Minutes and Seconds. The Seconds counter is incremented for every second, and its content checked for 60. When it reaches 60, it is reset to 0 and the Minutes counter is incremented by one. When the Minutes counter reaches 60, it is reset to zero and the Hour counter is incremented by one. Similarly, when the Hours counter reaches 13 it is reset to 1. The counter incrementing is done in decimal format. For every second the display is updated by the Hours, Minutes and Seconds registers. The program works in a continuous loop and displays time round the clock. The block diagram of the digital clock, the flow chart and the program are shown below. Digital Clock Basic Block Diagram D0-D7 PA4-A7 PA0-A3 RD WR PB4-B Hr Min A0-A7 ADDRESS DECODER PB0-B3 CS PC4-C7 PC0-C Sec K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 7

8 MICROPROCESSORS AND MICROCONTROLLER 8 FLOW CHART START INITIALIZE HR,MIN,SEC COUNTERS CALL DELAY SUBROUTINE FOR 1 SEC SEC SEC +1 N SEC >59? Y MIN MIN +1 SEC 0 N MIN >59? Y HR HR +1 MIN 0 N HR >12? HR 1 Y K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 8

9 MICROPROCESSORS AND MICROCONTROLLER Port Configuration: Control word formation: All the ports of 8255 are configured as output ports in Mode 0. (i.e) Port A, Port B, Port C : output, Mode: Simple I/O Therefore, the Control Word is: 80H Port C : to send Seconds value to 7 segment displays Port B: to send Minutes value to 7 segment displays Port A: to send Hour value to 7 segment display Program Label Mnemonics Comment Start: LXI D,HH00 ;(D) Hr LXI B,MMSS ; (B) Min, (C) Sec MVI A,80H ; (A) Control word for Port Conf. OUT CWR ; Move the Control word to Control Register of 8255 to configure the ports/ DISP: CALL DISPLAY ;Call display Subroutine to Display Hr,Min,Sec values on the 7 segment display DEL: CALL DELAY ; Call 1 sec Delay Subroutine INR C ; Sec Sec +1 MOV A,C ;Mov Sec to Acc CPI A,3C ; Is Sec >59 (ie) Sec =60? JNZ DEL ; If No (ZF!=1), Goto Label DISP MVI C,00 ; if Yes, set Sec 00 INR B ; Min Min +1 MOV A,B ; Move Min value to Acc K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 9

10 MICROPROCESSORS AND MICROCONTROLLER 10 CPI 3C ; Is Min >59 (ie) Min = 60? JNZ DEL ; If No (ZF!=1), Goto Label DISP MVI B,00 ; If Yes, set Min 00 INR D ;Hour Hour +1 MOV A,D ;Move Hour value to A CPI 0D ; if Hour >13? JNZ DEL ;If No (ZF!=1), Goto Label DISP MVI D,01 ; If Yes, set Hour 1 JMP DISP ; Jump to DISP HLT ;HALT Subroutine to Display Hour, Min, and Sec values DISP: MOV A, D ; (A) Hour Value DAA ; Get the BCD values OUT PORT A ; Display Hour value MOV A,B ; (A) Minute Value DAA ; Get the BCD value OUT PORTB ;Display Minute Value MOV A, C ; (A) Seconds DAA ;Get the BCD value OUT PORTC ; Display Seconds value RET ; Return K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 10

11 MICROPROCESSORS AND MICROCONTROLLER 11 1 Sec Delay Subroutine: DELAY: PUSH A PUSH B PUSH D LXI B,COUNT2 LOOP2: LXI D,COUNT1 LOOP1: DCX D MOV A,D ORA E JNZ LOOP1 DCX B MOV A,B ORA C JNZ LOOP2 RET ; Save the contents of registers ; used in the main program ; (BC) COUNT2 based on COUNT1 ; (DE) COUNT1 based on CLK freq. ;RETURN K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 11

12 MICROPROCESSORS AND MICROCONTROLLER 12 ZERO CROSS DETECTION A zero-crossing is a point where the sign of a mathematical function changes (e.g. from positive to negative), represented by a crossing of the axis (zero value) in the graph of the function. It is a commonly used term in electronics, mathematics, sound, and image processing. FREQUENCY MEASUREMENT Frequency measurement is a very important application of both counting and timing. Fundamentally, frequency measurement is a measure of how many times something happens within a certain known period. The use can be as diverse as how many counts are received per minute in Geiger Counter, how many cycles per second (hertz) there are in an electronic or acoustic measurement or how many wheel revolutions there are per unit of time in a speed of measurement. Both a counter and a timer are needed, the timer to measure the reference time and the counter to count the number of events within that time. To measure the frequency of a signal, the time period for half cycle is measured which is inversely proportional to the frequency. A sinusoidal signal is K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 12

13 MICROPROCESSORS AND MICROCONTROLLER 13 converted to square wave using a voltage comparator LM311 or OpAmp Lm747. A diode is used to rectify the output signal. A potential divider is used to reduce the magnitude to 5 volts. By the method of zero cross detection, the pulse width can be determined. A program can be used to sense the zero instant of the rectified square wave. The microprocessor measures the magnitude of the square wave at two consecutive points as shown in fig. The two magnitudes are compared and decision (i.e., whether the point is at zero instant) is taken on the basis of carry and zero flags. Various points of on the square wave are shown in fig. Very near to P3 at its left side the magnitude of square wave is zero and at P4, logic 1. The microprocessor subtracts the 1 st value from the 2 nd, so the result is non-zero and there is no carry. This is the basis of selection of zero instant point. Suppose the microprocessor takes reading at P1 and P2 where both magnitudes are zero. Difference of the two is zero. So this is not the zero instant of the wave. At points P5 and P6, the difference of the two values is zero, so it is also not a zero instant point. At P7, and P8, the difference is non-zero, but there is carry. So it is the end point of the half-square wave. As soon as the zero instant point is detected the microprocessor initiates a register pair to count the number how many times the loop is executed. [or start the timer to find the elapsed time between two zero instant points]. It crosses the loop when the magnitude of the square wave becomes zero. Thus the time for half cycle is measured. The count can be compared with stored numbers in a look-up table and the frequency can be displayed. K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 13

14 MICROPROCESSORS AND MICROCONTROLLER 14 FLOW CHART K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 14

15 MICROPROCESSORS AND MICROCONTROLLER 15 Port A of 8255 is configured as Input port and the signal whose frequency to be determined is connected to the Port line PA0. Program: START: MVI A,98 ;Get the control word OUT cwr ; Initialize the ports READ: IN PORTA ; Read voltage pulse at Port- A MOV B,A ; IN PORTA ; Read voltage pulse again CMP B ;Compare two readings JZ READ ; JC READ ; LXI B,0000; Initialize BC pair for counting LOOP: INX B IN PORTA ;Read voltage pulse RAR JC LOOP ;Check whether v has becomes zero. No goto Loop CALL LTAB; Call Lookup table Subroutine CALL DISP ; Call Display Subroutine HLT ;Stop LOOK UP TABLE COUNT FREQUENCY K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 15

16 MICROPROCESSORS AND MICROCONTROLLER Based Traffic Light Control System A simple traffic light system which has only two basic sequences of traffic is used in the model. First the traffic is allowed from North to South and from South to North direction. During this period, no traffic is allowed either way from East to West or from West to East. In the second sequence the condition is just reversed. (i.e) Vehicles movement from East to West and West to East is allowed, but North to South and South to North is not allowed. In both the sequences, free left is allowed. A typical road junction with the arrangement of Lamps is shown in the following fig. R RED Lamps to stop the traffic G Green Lamps to allow the traffic flow. Y Yellow Lamp to caution that traffic is about to start or about to stop. K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 16

17 MICROPROCESSORS AND MICROCONTROLLER 17 There are toally 12 LEDs/Lamps. In order to control the lamps the PPI 8255 is used in the system. The Port A and Port CLower of 8255 is used to connect the traffic lights as shown below. Lamp R1 G1 Y1 R2 G2 Y2 R3 G3 Y3 R4 G4 Y4 Port PC3 PC2 PC1 PC0 PA7 PA6 PA5 PA4 PA3 PA2 PA1 PA0 SeqA H 14H SeqB 1 0` H A2H SeqW 0 0` H 49H The above table also shows the respective control words to activate Sequence A, Sequence B and Sequence W (Warning indicator- Yellow) Program Logic. Step 1: Program the Ports A and Port C (lower) of 8255 as output ports in simple i/o mode. Step 2: Activate Sequence A Step 3: Wait for T1 seconds. Step 4: Activate the Sequence W Step 5: Wait for T2 seconds. Step 6: Actiave Sequence B Step 7: Wait for T1 seconds. Step 8: Activate the Sequence W Step 9: Wait for T2 seconds. Step 6: Go to Step 2 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 17

18 MICROPROCESSORS AND MICROCONTROLLER 18 Connection Diagram Program: As discussed in the class room. The The LEDs in the circuit can be replaced by high voltage lamps by using relay and a switching transistor as shown in the above figure. K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 18

19 MICROPROCESSORS AND MICROCONTROLLER 19 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 19

20 MICROPROCESSORS AND MICROCONTROLLER 20 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 20

21 MICROPROCESSORS AND MICROCONTROLLER 21 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 21

22 MICROPROCESSORS AND MICROCONTROLLER 22 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 22

23 MICROPROCESSORS AND MICROCONTROLLER 23 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 23

24 MICROPROCESSORS AND MICROCONTROLLER 24 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 24

25 MICROPROCESSORS AND MICROCONTROLLER 25 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 25

26 MICROPROCESSORS AND MICROCONTROLLER 26 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 26

27 MICROPROCESSORS AND MICROCONTROLLER 27 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 27

28 MICROPROCESSORS AND MICROCONTROLLER 28 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 28

29 MICROPROCESSORS AND MICROCONTROLLER 29 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 29

30 MICROPROCESSORS AND MICROCONTROLLER 30 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 30

31 MICROPROCESSORS AND MICROCONTROLLER 31 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 31

32 MICROPROCESSORS AND MICROCONTROLLER 32 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 32

33 MICROPROCESSORS AND MICROCONTROLLER 33 - Motor speed from nagoor kani - K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 33

34 MICROPROCESSORS AND MICROCONTROLLER 34 - K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 34

35 MICROPROCESSORS AND MICROCONTROLLER 35 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 35

36 MICROPROCESSORS AND MICROCONTROLLER 36 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 36

37 MICROPROCESSORS AND MICROCONTROLLER 37 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 37

38 MICROPROCESSORS AND MICROCONTROLLER 38 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 38

39 MICROPROCESSORS AND MICROCONTROLLER 39 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 39

40 MICROPROCESSORS AND MICROCONTROLLER 40 Frequency Measurement The sinusoidal voltage signal is stepped down to the desired level using voltage transformer and then is converted to square wave by using a zero crossing detector (ZCD). K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 40

41 MICROPROCESSORS AND MICROCONTROLLER 41 K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 41

42 MICROPROCESSORS AND MICROCONTROLLER 42 Ref: CTION+USING++microprocessor&hl=en&sa=X&ei=82YeVdX4BIaGuATJ- 4GwDg&ved=0CF0Q6A K.ELAMPARI, ASSOCIATE PROFESSOR OF PHYSICS, S.T.HINDU COLLEGE, NAGERCOIL. Page 42