1、The design of microcontroller-based signal generatorHuang Pengyong(Meizhou Bay Vocational Technical College, Putian, Fujian, 351 254)Abstract Waveform generator, a simple function signal generator, a produce a variety of waveforms, such as the triangle wave, sawtooth wave, square wave, sine waveform
2、 circuit. Function signal generator circuit experiments and equipment, instruments with a wide range of uses. By the principle of the function generator, as well as structure analysis, can be designed one can transform the triangle wave, sawtooth wave, square wave, sine function waveform generator.
3、Function signal generator signals in industrial production and scientific research to measure the performance and parameters of the components, electrical and electronic products index validation, parameter adjustment, and performance appraisal. Most of the commonly used signal generator by an analo
4、g circuit, this analog signal generator for low-frequency signal output often requires the RC value, so that not only the parameters of accuracy is difficult to guarantee, but the size and power consumption are large by the digital circuit composed of low-frequency signal generator, although its per
5、formance is good, but larger, more expensive, high-precision, wide amplitude modulation will become the trend of the digital signal generator. This article describes the 89C52 microcontroller and digital to analog converter DAC0832 to produce the desired signal of the low frequency signal source, th
6、e signal amplitude and frequency can be controlled as required. The article briefly describes the structure of principles and use of the DAC0832 digital-to-analog converter, the 89C52 basic theory and design of circuits a variety of chips. The paper focuses on how to use microcontroller to control t
7、he D / A converter to produce the hardware and software programming of the above signals. The signal frequency range is also adjustable as required.The core of the design tasks are: AT89C52 as the D / A converter and DAC0832 devices, circuit simulation software, design hardware drivers written in C,
8、 in order to achieve process control to produce sine wave, triangle wave, square wave, three commonly used low-frequency signals. Waveforms and enter any frequency value can be selected via the keyboard.Key words: on AT89C52 function waveform generator DAC0832 square wave, triangle wave, sine wave1
9、Introduction SCM is an integrated circuit chip, VLSI technology with data processing capability of the central processing unit CPU random access memory RAM, read only memory ROM, and a variety of I / O port and interrupt system, timers / timer other functions (which may also include a display driver
10、 circuit, pulse width modulation circuit, analog multi-channel converter, A / D converter and other circuit) integrated into a silicon constitute a small computer system.The waveform generator is a data signal generator, in the debugging of hardware, we often need to add some signal, whether it is n
11、ormal to observe circuit operation. General signal generator, not only cumbersome, but only made a few simple waveform, can not meet the need. Example, when users want to debug serial communication program, it is necessary on the computer to write a program, and then wire to connect the computer and
12、 the user target board, if not normal, do not know that the communication lines have a problem or a problem with the program. E2000 / L waveform generator capability, you can define the serial data. Output logic probe hook, quick and easy to debug.Based on a simple waveform generator of the microcon
13、troller is a common source, is widely used in the experiment of electronic technology, automatic control system and other scientific fields. At present, the composition of simple waveform generator There are many ways, such as type of DDS (Direct2Digital Synthesis) arbitrary waveform generator, usin
14、g a dedicated signal chip MAX038 AWG. The design stems from the 2007 National Undergraduate Electronic system to contest, through analysis and comparison with traditional methods to achieve the multi-function waveform generator. With high-performance single-chip high speed of operation, system integ
15、ration, strong advantages, the design of this signal generator, digital signal generator than the previous hardware is simple to understand and implement easier, clearer design ideas for the program, and easy to control and the advantages of the frequency and amplitude.The low-frequency signal gener
16、ator with the synthesis of single-chip waveform generator to produce high-precision, low distortion sine wave voltage can be used for the calibration frequency relays, synchronization relays, etc. can also be used as a low-frequency inverter power supply.Microcontroller as the core design of a low f
17、requency function signal generator. Signal generator with digital waveform synthesis techniques, through a combination of hardware circuitry and software programs can output custom waveforms such as sine, square, triangle spread to other arbitrary waveform. Waveform frequency and amplitude can be ar
18、bitrarily changed within a certain range. Waveform generation principle, hardware and software part of the design principles. MCU control the D / A converter to produce signals above hardware and software programming, of DAC0832 D, / A converter principle and use, AT89C52 and related to the design o
19、f the circuit chip, on different low-frequency signal source design. The signal generator has the advantages of small size, low price, stable performance, fully functional.2 System Design2.1 program: AT89C52 microcontroller programming method to produce sawtooth, sine wave, square wave three wavefor
20、ms, and then through the D / A converter DAC0832 digital signal converted to analog signals, filtered and amplified, and ultimately by the oscilloscope display, and keyboard to control three types of waveforms of the frequency changes, the final output shows the type and value.Design requirements1),
21、 the use of single-chip software design produces three waveforms2), three waveforms can be selected via the keyboard3) The waveform frequency is adjustable4), need to display the waveform types and frequency2.2 device selection1 by the MCU to control the D / A output three kinds of waveforms. AT89C5
22、2 microcontroller is a high-performance 8-bit single chip microcomputer. Which constitute the computers central processing unit CPU, memory, registers, the I / O interface to production in an integrated circuit chip, which constitute a relatively complete computer, and its cheap.3, the LCD monitor 1
23、602. Its power is small, the effect is obvious, and display the programming is easy to control, you can display the letters.2.3 The overall system design The system uses a microcontroller as the data processing and control of the core by the MCU to complete the man-machine interface, system control,
24、 signal acquisition and signal processing and transformation, using keystrokes, use the LCD display of the circuit output digital program. The design task is broken down into key circuits, liquid crystal display circuit modules. Figure 2-1 shows the overall block diagram of the system2.4 Hardware Im
25、plementation and unit circuit design2.4.1 of the smallest single-chip system design The 89C52 chip, ROM / EPROM MCU, this chip constitute the minimum system simple, and reliable. Constitute the minimum application system using the 89C52 microcontroller connected to the clock circuit and reset circui
26、t can be shown in the Figure 89C51 microcontroller minimum system. Due to the limit of integration, the minimum application can only be used as a small control unit. Its application features:(1) available to users of a large number of I / O port lines.(2) Internal memory capacity is limited.(3) appl
27、ication development is unique. The standard 52 for the 8K program space, 128 bytes of RAM, 32 ports, five interrupts, two timer / counter, 12 clock cycles to execute a basic instruction, the division of the longest for 48 cycles. 52 for the 8K program space, and 256 bytes of RAM, 32 ports, six inter
28、rupt, three timer / counters.2.4.2 D / A converter The DAC0832 is a dual in-line 8-bit D / A converter. Able to complete the digital input to analog output (current) conversion. Figure 3.5 shows the pin diagram of the DAC0832. Its main parameters are as follows: resolution of 8, the conversion time
29、of 1s, full scale error of 1LSB, the reference voltage (+10 / span -10) V, power supply (+5 to +15) V logic level inputs compatible with TTL. Be seen from Figure 3-1, the DAC0832 in two latches the first latch is called the input register, it allows the latched signal as ILE, the second latch called
30、 the DAC register, it the latch signal is also referred to as a channel control signal / XFER. Figure 2-3, when the ILE is high, the chip select signal / CS and the write signal / WR1 is low, the input register control signal, in which case, the output of the input register with the input changes. T
31、hereafter, when the high / WR1 low, the control signals become low at this time, the data is latched into the input register, input register output is no longer with the change of the external data DB.The second stage latch transfer control signal / XFER and write signal / WR2 at the same time is lo
32、w, the two latch control signal is high, the output of the 8-bit DAC register with the input, then when / WR2 from low, the control signal goes low, so the input register is latched into the DAC register.Figure 2-3 the rest of the pin function defined as follows:(DI7 DI0 in: 1) 8-bit data input, DI7
33、 highest.(2) IOUT1: analog current output terminal 1, when the data in the DAC register are all 1, the maximum output current, the DAC register data are all 0, the output current is 0.(3) IOUT2: analog current output, IOUT2 and IOUT1 and is a constant, that is IOUT1 the + IOUT2 = constant.(4) the RF
34、B: feedback resistor terminal of DAC0832 internal feedback resistor, RFB-side can be directly connected to an external op amps output, this is equivalent to a feedback resistor connected to the op amp output and input .(5) VREF: Reference voltage input, this end can be connected to a positive voltag
35、e can be accessed by a negative voltage, which determines the 0-255 digital transforming the amplitude of the analog voltage values, VREF range (+10 -10) V. Resistor network connected to the the VREF side and D / A internal T-shaped.(6) Vcc: chip supply voltage range of (+5 - 15) V.2.4.3 op amp circ
36、uit Figure 2-4, R1 is coupled to resistors, R2, R3, resistor voltage divider feedback. R2 and R1, the voltage ratio of 1:2, for OUT2 voltage of-5v 0v in the second op amp in the make-5v 0v between the voltage change-5v to 5v, the first op amp convert the amount of voltage values did not increase or
37、decrease the 1v, the second stage op amp voltage decrease or increase of 2v.2.4.4 LED display interface circuit Commonly used in LED display LED status display (commonly known as light-emitting diode) LED seven-segment display (commonly known as the digital control and LED 16 segment display, LED di
38、splay two states, for the system; digital tube for digital display; LED 16 segment display, for the character display)A. Digital control structure Digital tube consists of eight light-emitting diode (hereinafter referred to as fields), different combinations can be used to display the numbers 0-9. C
39、haracters AF and the decimal point . Digital tube is divided into two common cathode and common anode structure.Digital pipe works Total anode 8 digital tube light emitting diode anode (diode positive terminal) connected together. Usually common anode connected high a general power supply when a cat
40、hode connected to low, the digital tube conduction and light. A total of eight light-emitting diode digital cathode tube cathode (diode negative terminal) connected together. Public cathode connected to low (ground) when an anode connected to high, the digital tube light.2.4.5 Waveform Generation Pr
41、inciple and module design1 First, the digital value of the stored waveform memory array tosin;52 microcontroller to read the value in the array into the D / A converter;3, D / A converter input digital value is converted to analog output;4, the D / A analog output electric current through the op amp
42、 to convert the voltage output.Three waveforms generated by the microcontroller programming method through the DA converter module DAC0832 output into the filter wave amplification. Schematic 2-6 as follows:2.4.6 the design of the display module LCD 1602 display the output waveform, frequency, the c
43、ircuit diagram. As shown in Figure 2-7, the 1602 data of the eight termination microcontroller P1 port, its three P3.2-P3.4 can end RS, RW, E, respectively, then the microcontroller. Through software control of the LCD screen can display the waveform types and frequency of the waveform.Conclusions T
44、he curriculum design allows me to deepen and improve the theoretical knowledge learned on the course. And through the course design, so that I understand and master microcomputer application system software and hardware design process, methods and implementation, training me to analyze problems and
45、problem-solving skills, to lay a good foundation for the future design and implementation of the more difficult applications. At the same time trained me to write the design specifications. In the design process, I found a lot of problems before done such a design, but this design really made me gro
46、w a lot. Single-chip design, the hardware circuit is relatively simple, mainly is to solve the problem of program design, program design is a very flexible thing, it reflects you solve the problem of logical thinking and innovation capability, it is the soul of a design lies. Therefore, most of the
47、time throughout the design process is used in the program above. Many subroutines can learn from books, but how the convergence of each subroutine is the key problem, which requires very familiar with the structure of the microcontroller. Therefore we can say that the single chip design is a combina
48、tion of software and hardware, the two are inextricably linked. To design a successful circuit, must be patient, there must uphold the determination. , Spend the most time on the details of the design of each unit circuit connections and circuits, such as the choice of a variety of programs, we care
49、fully compare the analysis of the principle as well as possible reasons for the circuit design process. This requires a full and thorough understanding and research, and the various component parts of the hardware system of flexible applications. Books of theoretical knowledge on the basis of the design is complete, I have a deeper understanding. The desi
陕公网安备 61072602000132号 违法和不良信息举报：0916-4228922