INTERFACING ADC/DAC. DAC INTERFACE SECTION: DAC 0800 is a monolithic, high speed, current output D/A Converter. Its unique features are:

Size: px

Start display at page:

Download "INTERFACING ADC/DAC. DAC INTERFACE SECTION: DAC 0800 is a monolithic, high speed, current output D/A Converter. Its unique features are:"

Amice Patterson
5 years ago
Views:

1 INTERFACING ADC/DAC AIM: a) To interface the DAC unit to microprocessor and to write an ALP to convert the given digital word to analog voltage and also to generate sawtooth, triangular and sinewaves. b) To interface ADC unit to microprocessor and to write an ALP to convert the given analog voltage to digital word. APPARATUS REQUIRED: 8085 microprocessor kit, ADC/DAC interfacing board, CRO probe, CRO, power supply(variable), digital multimeter and connecting wires. THEORY: DAC INTERFACE SECTION: DAC 0800 is a monolithic, high speed, current output D/A Converter. Its unique features are: Typical settling time of 100ns Complementary current outputs Differential output voltages of 20V peak to peak with simple resistor load 2-quadrant wide range multiplying capability The DAC interface section comprises of i. I/O Decoding ii. D/A conversion circuit

2 I/O DECODING: The IC s 74LS138 and 74LS00 form the address decoding logic in this interface board. The address lines A3, A4 and A5 are connected to pin 1, pin2 and pin3 of 74LS138 respectively. The address lines A6 and A7 are Nanded together and the Nand gate output is connected to pin 6 of 74LS138. Pin 4 is ground. Thus with A7 A6 A5 A4 A3 A2 A1 A X X X =C0(hex) DAC1 is selected. D/A CONVERSION CIRCUIT: The design comprised of the latch 74LS273, DAC 0800 and the current to voltage converting circuitry using OPAMP-741. DAC 0800 is configured for bipolar output operation. Current to voltage conversion circuit is designed using OPAMP-741. This circuit converts the current output of DAC 0800 into equivalent analog voltage. Complimentary current outputs IOUT, IOUT are connected to inverting and non-inverting output of OPAMP-741. In order to have the output voltage variation from -5V to +5V, a 2.2 feedback resistor has been selected.

3 The DAC outputs are available at the 5 pin connector (P3). DAC output is terminated at pin 10 of the connector P3. ADC INTERFACE SECTION: ADC-0809 is a monolithic CMOS device, with an 8-bit A/D converter, 8channel multiplexer and microprocessor compatible control logic. The main features of ADC-0809 are, 1. 8-bit resolution µs conversion time 3. 8-channel multiplexer with latched control logic 4. No need for external zero or full scale adjustment 5. Low power consumption 15mw 6. Latched tristate output I/O DECODING: The device contains 2-channel single ended analog signal multiplexer. A particular input channel is selected by using the address decoder. Table shows the input states for the address lines to select any channel. The address is latched into the decoder on the low to high transition of the address latch enable signal (ALE). The A/D converter s successive approximation register is reset on the positive edge of the start conversion pulse. The conversion is begun on the falling edge of SOC. End of conversion will go low between 0 to 8 clock pulses after the rising edge of start of conversion. Selected analog Address line signal ADD C ADD B ADD A IN

4 IN1 IN2 IN3 IN4 IN5 IN6 IN A/D CONVERSION CIRCUIT: The channel select address pins ADD A, ADD B, ADD C and ALE of ADC0809 are connected to the Data bus through a latch 74LS174. The eight data outputs of ADC-0809 are connected to D0-D7 through a buffer 74LS244. Provision is also made to display the data output by means of LEDs, using a latch 74LS374. This latch is allotted by the End of conversion signal. Thus, after the conversion is completed, at the rising edge of EOC, the 74LS374 latches the digital output of ADC0809. The LEDs which are connected to output pins of the latch, display the digital data automatically. The EOC of ADC0809 can be connected to RST5.5 or RST6.5 or RST7.5. So the EOC output can be used to interrupt the CPU in turn, can input the digital data from ADC0809. Moreover the EOC output is connected to D0 through a tristate buffer 74LS125. Thus the transfer of data is also possible by means of polling. Start of conversion can be given externally using the SOC Switch available on board. SOC can also be controlled using the D flip flop 74LS74. PCLK available at the VXT Bus is divided by 2 by the D flip flop 74LS74 to provide a input clock of 750KHz to ADC.

5 The channel inputs (IN0-IN7) are terminated at a 12 pin header. A 1K trimpot can be used for demonstration purposes. It is connected to channel 0, however provision is also there onboard for connecting channel 1 to 7. A 3 to 8 decoder 74LS138 is employed to generate I/O decoding logic. Pin-1, Pin-2 and Pin-3 of 74LS138 are connected to address lines A3, A4 and A5 respectively. Thus, the buffer 74LS244 which transfers the converted data outputs to databus is selected when A7 A6 A5 A4 A3 A2 A1 A X X X =C8(hex) The I/O address for the latch 74LS174 which latches the databus to ADD0, ADD1, ADD2 and ALE is A7 A6 A5 A4 A3 A2 A1 A X X X =E0(hex) The start of conversion pulse can be given by means of software also. The flip flop 74LS74 which transfers the D0 line status to the SOC pin of the ADC0809 is selected, when A7 A6 A5 A4 A3 A2 A1 A X X X =D0(hex)

6 The EOC output of ADC0809 is transferred to the data line D0, when 74LS125 is selected with address, A7 A6 A5 A4 A3 A2 A1 A X X X =D8(hex) PROGRAM-1: AIM: To obtain a output of 0 volts at DAC1. Since DAC0800 is an 8-bit DAC and the output voltage variation is between -5V to +5V. The digital data input and the corresponding output voltages are presented in the following table. Input Data in Hex F.. FD FE FF Output Voltage Execute the following program and observe that the output voltage at DAC1 is 0 volts.

7 MEMORY LOCATION OP-CODE LABEL MNEMONICS 3E,7F D3,C0 76 ORG 4100H MVI A, 7F OUT C0H HLT PROGRAM-2: AIM: To create a saw tooth wave at the output of DAC1.Output digital data from 00 to FF in constant steps of 01 to DAC1. Repeat this sequence again and again. As a result, a saw-tooth wave will be generated at DAC1 output. MEMORY LOCATION OP-CODE LABEL MNEMONICS 3E, 00 D3, C0 3C C2, 02, 41 C3, 00, 41 START L1 ORG 4100H MVI A, 00 OUT C0H INR A JNZ L1 JMP START PROGRAM-3: To generate a triangular waveform at DAC1 output. The following program will generate a triangular wave at DAC1 output.

8 MEMORY LOCATION B 410C 410E 410F 4112 OP-CODE LABEL MNEMONICS 2E, 00 7D D3, C0 2C C2, 02, 41 2E, FF 7D D3, C0 2D C2, 0B, 41 C3, 00, 41 START L1 L2 ORG 4100H MVI L, 00 MOV A, L OUT C0H INR L JNZ L1 MVI L, FFH MOV A, L OUT C0H DCR L JNZ L2 JMP START PROGRAM-4: AIM: To generate a sine-wave at DAC1 output. A lookup table is provided in the program for sine-wave generation. Output data continuously to DAC1 from this lookup table. Verify, using a CRO at DAC1 output, that the waveform is a sinewave. The data for lookup table is arrived by experiment. MEMORY LOCATION OP-CODE LABEL MNEMONICS 21, 10, 41 0E, 46 7E D3, C0 23 0D START LOOP ORG 4100H LXI H, 4110H MVI C, 46 MOV A, M OUT C0H INX H DCR C

9 410A 410D C2, 05, 41 C3, 00, 41 JNZ LOOP JMP START LOOKUP: MEMORY LOCATION C C C C DATA 7F, 8A, 95, A0 AA, B5, BF, C8 D1, D9, E0, E7 ED, F2, F7, FA FC, FE, FF, FE FC, FA, F7, F2 ED, E7, E0, D9 D1, C8, BF, B5 AA, A0, 95, 8A 7F, 74, 69, 5F 53, 49, 3F, 36 2D, 25, 1D, 17 10, 0B, 07,04 01, 00, 01, 04 07, 0B, 10, 17 1D, 25, 2D, 36 3F, 49, 53, 5F 69, 74 PROGRAM-5: AIM: In a real-time application, input of data and processing of data are indispensable. The following programs initiate the conversion process, checks the EOC pin of ADC-0809 as to whether the conversion is over and then inputs

10 the data to the processor. It also instructs the processor to store the converted data at RAM location 4150 (hex). MEMORY LOCATION OP-CODE LABEL MNEMONICS A 410C 410D 410E 410F C 411E E, 00 D3, E0 3E, 08 D3, E0 3E, 01 D3, D0 AF AF AF 3E, 00 D3, D0 DB, D8 E6, 01 FE, 01 C2, 13, 41 DB, C8 32, 50, START LOOP MVI A, 00 OUT E0 MVI A, 08 OUT E0 MVI A, 01 OUT D0 XRA A XRA A XRA A MVI A, 00 OUT D0 IN D8 ANI 01 CPI 01 JNZ LOOP IN C8 STA 4150H HLT Execute this program. Compare the data displayed at the LEDs with that stored at location 4150H.

11 FREQUENCY MEASUREMENT Aim: To measure the frequency of the sine waveform. Apparatus required: Bread board, Connecting wires, resistors, Op-amp, CRO, Function generator, CRO probes, Power supply, Microprocessor kit. Theory: The sine wave whose frequency is to be measured can be applied to zero crossing detector. Since the number of zero crossings for every cycle is two, the number of zero crossing for a time interval of 0.5 seconds is equal to frequency. For this a square wave form of frequency 1 Hz. is generated using 8253 operating it in mode 3 and rising edge of the square wave form is checked. Once the raising edge is found the number of zero crossings is counted until the falling edge of the square wave. This count is equal to frequency and can be displayed on address field. To generate a square wave of 1 Hz frequency the 8253 is kept in mode 3. Since the clock frequency is 3 MHz, the count required to generate square wave of 1 Hz is Count= The clock frequency/the desired frequency of square wave = /1= Since the maximum count that can be loaded in a 16 bit counter is 65,535, we have to use two counters for count value. 3,00,00. So we use the first counter with a count 3000 and second counter with a count We use two counters counter 0 with count 3000 and the counter 1 with a count Circuit Diagram

Algorithm 1. Initialize BC register to 0000. 2.

12 Algorithm 1. Initialize BC register to Initialize port A and port B of 8255 as input ports 3. Initialize counter 0 in mode 3

13 4. Load the count 3000 in the counter 5. Initialize counter 1 in mode 3 6. Load the count 1000 in the counter 7. Read port B0 pin 8. Check for rising edge of the square wave form 9. If it is found read port A0, Otherwise go to step Call subroutine synch that find falling edge of the output of ZCD 11. Find falling edge 12. Increment count. 13.Call subroutine for finding rising edge 14. If rising edge is found increment the count 15. Read port B0. If it is high go to step 10, otherwise 16. Call subroutine conversion that convert the BC register contents in to single digits and store from locations form Call subroutine display that display the contents of data stored from locations 4600 to 4603 on address field 18.Stop th eprogram Subroutine synch 1. Read Port A 2. And Immediate with Check for zero, if it is not go to step1 3. Else return to main program Subroutine REDGE 1. Read Port A 2. And Immediate with Check for non-zero, if it is not go to step1 3. Else return to main program

14 Subroutine Conversion 1. Get the contents of C register and separate in to two digits. 2. Store the digits in locations 4602 and Get the contents of B register and separate in to two digits. 4. Store the digits in locations 4600 and Return to main program Subroutine Display 1. Push the contents of PSW and BC register pair to stack pointer 2. Initialize 8279 to display the contents on Address field 3. Initialize HL register pair with Call monitor program which display the contents of 4600 to 4603 on address field 5. Retrieve the contents of PSW and BC register from stack pointer. 6. Return to main program PROGRAM: MEMORY MACHINE LABEL NEMONICS LOCATION CODE ,00,00 LXI B, E,92 MVI A, D3,0F OUT 0F E,37 MVI A, D3,CE OUT CE 410B 3E,00 MVI A,00 410D D3,C8 OUT C8 410F 3E,30 MVI A, D3,C8 OUT C E,77 MVI A, D3,CE OUT CE E,00 MVI A,00

15 4119 D3,CA OUT CA 411B 3E,10 MVI A,10 411D D3,CA OUT CA 411F DB,0D LOOP IN 0D 4121 E6,01 ANI CA,1F,41 JZ LOOP 4126 CD,00,42 LOOP1 CALL SYNC INXB 412A CD,00,43 CALL REDGE 412D 03 INX B 412E DB,0D IN 0D 4130 E6,01 ANI C2,26,41 JNZ LOOP CD,50,41 CALL CONVERSION 4138 CD,00,45 CALL DISPLAY 413B 76 HLT CONVERSION: MEMORY MACHINE LABEL NEMONICS LOCATION CODE MOV A,C 4151 E6,0F ANI 0F ,03,46 STA MOV A,C 4157 E6,F0 ANI F F RRC 415A 0F RRC 415B 0F RRC 415C 0F RRC 415D 32,02,46 STA MOV A,B

16 4161 E6,0F ANI 0F ,01,46 STA MOV A,B 4167 E6,F0 ANI F F RRC 416A 0F RRC 416B 0F RRC 416C 0F RRC 416D 32,00,46 STA C9 RET SYNC: MEMORY MACHINE LABEL NEMONICS LOCATION CODE 4200 DB,0C IN 0C 4202 E6,01 ANI C2,00,42 JNZ SYNC 4207 C9 RET REDGE: MEMORY MACHINE LABEL NEMONICS LOCATION CODE 4300 DB,0C IN 0C 4302 E6,01 ANI CA,00,43 JZ REDGE 4307 C9 RET DISPLAY: MEMORY MACHINE LABEL NEMONICS LOCATION CODE 4500 F5 PUSH PSW 4501 C5 PUSH B

17 4502 3E,03 MVI A, E,09 MVI C, ,00,46 LXI H, CD,05,00 CALL C C1 POP B 450D F1 POP PSW 450E C9 RET

18 STEPPR MOTOR INTERFACE AIM: To interface the given stepper motor to 8085 Microprocessor kit and write an ALP to run the motor in both clockwise and anticlockwise directions. APPARATUS REQUIRED: THEORY: Stepper motor, microprocessor kit, stepper motor, interfacing unit STEPPER MOTOR: A motor in which the rotor is able to assume only discrete stationary angular displacement is a stepper motor. The rotary motion occurs in a stepwise manner from one equilibrium position to the next. Stepper motor control is a very popular application of microprocessor in control area. They are widely used in (simple position control systems in the open and closed loop mode) a variety of application such as computer peripherals (printers, disk driver, etc..) and in the areas of process control machine tools, medicine, numerically controlled machines and robotics. CONSTRUCTIONAL FEATURES: where, NS * Nr Ns is the No. of the stator poles. Nr is the No. of pairs of the rotor poles. Generally step size of the stepper motor depends upon Nr. These stable positions can be attained by simply energising the winding on any one of the stator poles with a DC. There are three different schemes available for stepping a stepper motor. These are: (a) Wave scheme (b) 2-phase scheme and (c) Half stepping or mixed scheme. Here we are going to use 2-phase scheme for stepping a stepper motor.

19 2-PHASE SCHEME: In this scheme, any two adjacent stator windings are energised. There are two magnetic fields active in quadrature and none of the rotor pole face can be in direct alignment with the stator poles. A partial but symmetric alignment of the rotor poles is of course possible. Typical equilibrium conditions of the rotor when the windings on two successive stator poles are excited are illustrated in the fig. In step (a), A1 and B1 are energised. The pole-face S1 tries to align itself with the axis of A1 (N) and the pole face S2 with B1 (N). The north pole N3 of the rotor finds itself in the neutral zone between A1 (N) and B2 (N). S1 and S2 of the rotor, position themselves symmetrically with respect to the two stator north pole. Next, when B1 and A2 are energised. S2 tends to align with B1 (N) and S3 with A2 (N). Of course, again under equilibrium conditions, only partial alignment is possible and N1 finds itself in the neutral region, midway between B1 (N) and A2 (N) [step (b)]. In step (c), A2 and B2 are on. S3 and S1 tend to align with A2 (N) and B2 (N), respectively with N2 in the neutral zone. Step (d) illustrates the case when A1 and B2 are on. The step angle is 30 0 as in the wave scheme. However, the rotor is offset by 15 0 in the 2-phase scheme with respect to the wave scheme. A total of 12 steps are required to move the rotor by (mechanical). 2-phase drives produce more torque than the wave drives. The switching sequence for the 2-phase scheme is given in the below table: ANTICLOCKWISE CLOCKWISE STEP A1 A2 B1 B2 steps A1 A2 B1 B DRIVING CIRCUITRY: Stepper motor requires logic signals of relatively high power. In these boars the silicon Darlington pair (TIP 122) transistors are used to supply that required power. The driving pulses are generated by the interface circuit. The input for the interface circuit is TTL pulses generated under software control using the microprocessor kit. The TTL levels of

20 pulses sequence from the data bus is translated to high voltage output pulses using a buffer 7407 with open collector. The darlington pair transistor (TIP 122) drive the stepper motor as they withstand higher current. A 220 ohm resistor and an IN 4148 diode are connected between the power supply and darlington pair collector for supporting fly back current. The data lines D0-D3 and D4-D7 are used to drive the 8 TIP 122 available on this board as shown in the appendix A. The four collector points of each TIP 122 are brought to two 5 pin connectors P2 & P3 to connect two different stepper motors. With this board it is possible to connect stepper motor of torque ranging from 2kg to 20kg wit operating voltages of 12V, 24V, & 6V. PROGRAM: To run a stepper motor for required angle within which is equivalent to 256 steps. Memory location Machine codes label Nemonics 4100 OE HEX DATA MVI C, HEX DATA START LXI H, LOOK UP MVI B, E REPT MOV A,M 4108 D3 C0 OUT CO 410A 0D DCR C 410B CA JZ END 410E LXI D,COUNT DELAY NOP B DCX D B MOV A,E 4114 B2 ORA D 4115 C JNZ DELAY INX H DCR B 411A C JNZ REPT 411D C JMP START A LOOK DB A UP END HLT

21 PROGRAM: To run stepper motor in both forward and reverse directions with delay. Memory location Machine codes label Nemonics 4100 ORG 4100H 4100 OE 20 START MVI C, 20H F 41 FORWD LXI H, FORLOOK 4105 CD CALL ROTATE 4108 OD DCR C 4109 C JNZ FORWD 410C CD CALL STOP 410F OE 20 MVI C,20H REVES LXI H,REVLOOK 4114 CD CALL ROTATE 4117 OD DCR C 4118 C JNZ REVES 411B CD CALL STOP 411E C JMP START

22 ROTATE MVI B,04H E REPT MOV A,M 4124 D3 C0 OUT 0C0H LXI D,0303H B LOOP 1 DCX D 412A 7B MOV A,E 412B B2 ORA D 412C C JNZ LOOP1 412F 23 INX H DCR B 4131 C JNZ REPT 4134 C9 RET FF FF STOP LXI D,FFFFH B LOOP 2 DCX D B MOV A,E 413A B2 ORA D 413B C JNZ LOOP 2 413E C9 RET 413F A FORLOOK DB 09H,05H,06H,0AH A REVLOOK DB 0AH,06H,05H,09H END HLT

23 TRAFFIC LIGHT CONTROL INTERFACE AIM: To interface the traffic light control system board to 8085 microprocessor kit and write an assembly language program for the given traffic conditions. APPARATUS REQUIRED: 8085 microprocessor kit, traffic light control system board, 26 pin port THEORY:

24 Figure shows a simple arrangement and pin connections for microprocessor based traffic control. All ports of 8255 have been programmed as output ports. Three types of LED s have been used, red, yellow and green. Green light glows to allow crossing, yellow to make alert and red does not allow crossing. Eight dual colour LED s are provided for pedestrian crossing. These LED s change their colour to red or to green. When the LED is ON it shows green colour and when it is OFF it shows red colour. The following traffic control states are for the experiment: State1: Vehicles can go from South to North. State2: Wait state. State3: Vehicles can go from East to West. State4: Wait state. State5: Vehicles can go from North to South. State6: Wait state. State7: Vehicles can go from West to East. State8: Wait state. State9: All pedestrians can cross. State10: Wait state. Since the LED is an output device, all 8255 ports are assumed to be output ports in mode 0. Therefore the control word is 80H. For the state 1, the green LED connected to pin PA 4 must glow and the red LED s connected to pins PA 1, PB 3, PA 3 must glow. Also pedestrians must be in OFF conditions. Therefore the data that is to be sent to the ports A, B and C are 1A, F8, 00 respectively. DIRECTIONS PA 7 PA 6 PA 5 PA 4 PA 3 PA 2 PA 1 PA 0 DATA South-North A DIRECTIONS PB 7 PB 6 PB 5 PB 4 PB 3 PB 2 PB 1 PB 0 DATA South-North F8

25 The above data is sent to the respective port to allow the vehicle from south to north. Similarly all the data s are sent to the port for the further process Port A Data table: DIRECTIONS PA 7 PA 6 PA 5 PA 4 PA 3 PA 2 PA 1 PA 0 DATA South-North A Wait East-West Wait A8 North-South A Wait West-East Wait All pedestrians A Wait A Port B Data table: DIRECTIONS PB 7 PB 6 PB 5 PB 4 PB 3 PB 2 PB 1 PB 0 DATA South-North F8 Wait F8 East-West FA Wait F4 North-South F1 Wait F4 West-East F8 Wait F8 All pedestrians Wait F8

26 Program Memory location A 410C 410F A 411C 411E B 412D B 413D 413F E,80 D3,OF 3E,1A D3,OC 3E,F8 D3,OD CD,85,41 3E,68 D3,OC 3E,F8 D3,OD CD,75,41 3E,88 D3,OC 3E,FA D3,OD CD,85,41 3E,A8 D3,OC 3E,F4 D3,OD CD,75,41 3E,8A D3,OC 3E,F1 D3,OD CD,85,41 3E,86 D3,OC 3E,F4 D3,OD CD,75,41 3E,83 D3,OC code Label Mnemonics Comments START MVIA,80 OUT OF MVIA,1A OUT OC MVIA,F8 OUT OD CALL DELAY1 MVIA,68 OUT OC MVIA,F8 OUT OD CALL DELAY2 MVIA,88 OUT OC MVIA,FA OUT OD CALL DELAY1 MVIA,A8 OUT OC MVIA,F4 OUT OD CALL DELAY2 MVIA,8A OUT OC MVIA,F1 OUT OD CALL DELAY1 MVIA,86 OUT OC MVIA,F4 OUT OD CALL DELAY2 MVIA,83 OUT OC Initialize all ports in Output port Send port A and port B data of state 1 to respective ports Send port A and port B data of wait state to respective ports Send port A and port B data of state 2 to respective ports Send port A and port B data of wait state to respective ports Send port A and port B data of state 3 to respective ports Send port A and port B data of wait state to respective ports Send port A and port B

27 414A 414C 414E C 415E B 416D 416E A 417B 417C 417D A 418B 418C 418D E,F8 D3,OD CD,85,41 3E,86 D3,OC 3E,F8 D3,OC CD,75,41 3E,8A D3,OC 3E,08 D3,OD CD,85,41 3E,4A D3,OC 3E,F8 D3,OD CD,75,41 C3,04,41 OE,14 21,94,F6 2B 7D B4 C2,7A,41 OD C2,77,41 C9 OE,14 21,94,F6 2B 7D B4 C2,8A,41 OD C2,87,41 C9 DELAY 2 LOOP 2 LOOP 1 DELAY 1 LOOP 4 LOOP 3 MVIA,F8 OUT OD CALL DELAY1 MVIA,86 OUT OC MVIA,F8 OUT OC CALL DELAY2 MVIA,8A OUT OC MVIA,08 OUT OD CALL DELAY1 MVIA,4A OUT OC MVIA,F8 OUT OD CALL DELAY2 JUMP START MVIC,14 LXIH,F694 DCX,H MOV A,L ORA,A JNZ LOOP1 DCR, C JNZ LOOP2 RET MVIC,84 LXIH,93F2 DCX,H MOV A,L ORA,A JNZ LOOP3 DCR,C JNZ LOOP4 RET data of state 4 to respective ports Send port A and port B data of wait state to respective ports Send port A and port B data of state 5 to respective ports Send port A and port B data of wait state to respective ports Initialize count Initialize count

MICROPROCESSORS AND MICROCONTROLLER 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,