CN104537905B - PCM pulse code modulation (PCM) principle based on microprocessor resolves experimental technique and system - Google Patents
PCM pulse code modulation (PCM) principle based on microprocessor resolves experimental technique and system Download PDFInfo
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Abstract
The invention discloses a kind of PCM pulse code modulation (PCM) principle based on microprocessor and resolve experimental technique and system, comprise and input simulating signal is carried out band limit, sampling, quantized and coded treatment; Use a STM32 microprocessor by analog signal waveform, sampling time, quantized value, binary coding code character simultaneous display in a liquid crystal display.Simultaneous display simulating signal while of present invention achieves on one screen, sampling time, quantized value, binary coding group, solve the problem that conventional P CM pulse code modulation (PCM) experiment oscillograph directly can not show quantized value and scale-of-two code character, can observatory control signal waveform intuitively by student of the present invention, sampling time, quantized value, at phase place and corresponding relation numerically between scale-of-two code character, contribute to the understanding of student to PCM pulse code modulation (PCM) principle and process, simultaneously owing to no longer needing 4 oscilloscope channels, save loaded down with trivial details complex operations, time spent by debug process.
Description
Technical field
The present invention relates to communication field, particularly a kind of PCM pulse code modulation (PCM) principle based on microprocessor resolves experimental technique and system, is that a kind of PCM pulse code modulation (PCM) principle based on STM32 microprocessor resolves experimental technique and system.
Background technology
Modern communications is digital communication mainly, namely the process of analog signal figure is message sink coding, PCM pulse code modulation (PCM) is a kind of conventional source coding method, PCM pulse code modulation (PCM) principle is an important knowledge point in colleges and universities' " digital communication theory " course, also be a difficult point in teaching, how disclose principle and the process of PCM pulse code modulation (PCM) by laboratory facilities intuitively, help student to understand abstruse abstract knowwhy, be the problem needing solution in teaching badly always.
Complete PCM pulse code modulation (PCM) process comprises simulating signal band limit, sampling, quantize, coding link, student only understanding of the relation between simulating signal bandwidth sum sampling frequency, and on this basis by the relation of the quantized value that engraves during analytical sampling and binary coding interblock, reach the object understood and grasp PCM pulse code modulation (PCM) principle and different modes message sink coding feature, for this reason, sampling pulse relative with correspondence position on a timeline in simulating signal fixing (synchronously) must be ensured, namely require that the sampled signal amplitude of certain sampling time is the amplitude of simulating signal in the same time, the then amplitude of this moment simulating signal, sampled signal amplitude, quantized value, binary coding code character is corresponding relation one by one.
The experiment of conventional P CM pulse code modulation (PCM) is that the experiment module circuit consisted of special coding and decoding chip realizes, and the signal that student can observe has input simulating signal, 8KHZ sampling pulse, encoded clock, coded signal.Just need 4 oscilloscope channels to observe above-mentioned 4 signals as PCM pulse code modulation (PCM) principle will be analyzed preferably simultaneously, only in this way just can observe the corresponding position in simulating signal of sampling time, corresponding relation between code rate and coding waveforms three, because sampling pulse in experimental system and simulating signal are under different clock sources controls, can not ensure that the sample position of sampling pulse in simulating signal is relatively fixing, cause simulating signal through sampling, the lowest order code element of the scale-of-two code character quantizing and obtain after coding be can not determine, according to the signal of oscilloscope, student can not obtain the scale-of-two code character determined, simultaneously because oscillograph can only display waveform, directly can not show numerical value, as quantized value and binary code, student also needs to restrain coding schedule to analyze the relation between quantized value and scale-of-two code character by A rule or U, reach the object understood and grasp PCM pulse code modulation (PCM) principle, so do not observe quantized value and scale-of-two code character intuitively by the experiment of conventional P CM pulse code modulation (PCM), intuitively can not reflect sampled signal values, quantized value, relation between scale-of-two code character three, therefore conventional P CM pulse code modulation (PCM) experimental technique cannot show cataloged procedure, not obvious to the help of student's understanding and grasp PCM pulse code modulation (PCM) principle.
Nonetheless, the oscillograph completing above-mentioned experiment must be 4 oscilloscope channels, because watch 4 signal waveforms with two dual channel oscilloscopes, 4 signals cannot be observed at phase place and temporal corresponding relation, but the oscillograph that Scientific Research in University Laboratory is equipped with at present is generally dual channel oscilloscope or single channel oscillograph, because the relative complicated operation of 4 oscilloscope channel, debug process expends time in.
Summary of the invention
The object of the invention is to provide the PCM pulse code modulation (PCM) principle based on microprocessor to resolve experimental technique and system, is resolve experimental technique and system based on the PCM pulse code modulation (PCM) principle of STM32 microprocessor, for described problem, this experimental system guarantees absolute synchronization between simulating signal and sampling pulse by STM32 software synchronization algorithm, simultaneously by control STM32, same LCDs observes analog signal waveform simultaneously, sampling time on time shaft, sampled signal, quantized value, binary coding group 5 signals, accurately demonstrate the quantized value size corresponding to a certain sampling time, accurately demonstrate the scale-of-two code character that this moment quantized value is corresponding, tackle above-mentioned output signal, also synchronism output coding waveforms and PCM sampling pulse waveform, observed by oscillograph, be convenient to liquid crystal on show scale-of-two code character contrast, synchronism output decoded signal, is observed by oscillograph, and comparison band limit audio analog signals, analyzes and quantize error size.
To achieve these goals, the solution of the present invention is:
PCM pulse code modulation (PCM) principle based on microprocessor resolves experimental technique, comprises and input simulating signal is carried out to band limit, sampling, quantized and coded treatment; Wherein, described method is that sampling time on use STM32 microprocessor outputting analog signal waveform, time shaft, sampled signal, quantized value, binary coding group simultaneous display are in a liquid crystal display.
Scheme is further: the processing procedure of described simultaneous display is:
The first step: set up a level of synchronization axle on a liquid crystal display, described transverse axis is the time shaft based on described processor working frequency;
Second step: the A/D change-over circuit using microprocessor, samples to input simulating signal with the A/D sampling frequency of 64KHZ, and demonstrate the envelope of sampled signal in described liquid crystal display, form the input analog signal waveform of corresponding time shaft;
3rd step: according to the PCM sampling frequency of PCM pulse code modulation (PCM) rule, microprocessor carries out PCM sampling to described simulating signal, described analog signal waveform is made PCM sampling time mark, PCM sampled signal simultaneous display the below that sampling time marks or above.
4th step: microprocessor quantizes described PCM sampled signal, quantized value simultaneous display corresponding to each PCM sampled signal the below that sampling time marks or above.
5th step: microprocessor carries out binary coding to described quantized value, scale-of-two code character simultaneous display corresponding to each quantized value the below that sampling time marks or above.
Scheme is further: described method comprises the step of Signal aspects debugging further, comprising:
The first step a: computing machine is connected STM32 microprocessor chip by an ARM emulator;
Second step: write operation one on computers and described input simulating signal is carried out being with limit, sampling, to quantize and coded treatment, simultaneous display is in the program of a liquid crystal display;
3rd step: carry out program function simulation by ARM emulator, simultaneous computer is debugged described program, is entered by download program in STM32 microprocessor chip after having debugged;
4th step: ARM emulator and computing machine are departed from STM32 microprocessor chip, STM32 microprocessor chip independent operating.
Scheme is further: described PCM sampling frequency is 8KHZ.
Scheme is further: described binary coding mode is that the A of 8 restrains 13 broken lines codings.
Scheme is further: the sampling time on outputting analog signal waveform, time shaft, sampled signal, quantized value, binary coding code character simultaneous display are while a liquid crystal display, described method comprises further: tackle above-mentioned output signal, also synchronism output coding waveforms and PCM sampling pulse waveform, described waveform is observed for oscillograph, with the scale-of-two code character comparison that shows on liquid crystal.
PCM pulse code modulation (PCM) principle based on microprocessor resolves experimental system, comprises STM32 microprocessor chip, is provided with a frequency range at the bandwidth limitation circuit of 300HZ-3400HZ and digital lcd around described microprocessor chip; The input end of described bandwidth limitation circuit connects audio analog signals Acquisition Circuit, the output terminal of described bandwidth limitation circuit connects the A/D conversion input interface of microprocessor chip, liquid crystal display connects the DOL Data Output Line of described microprocessor chip by interface circuit, and the output of described bandwidth limitation circuit is provided with a band limit simulated audio signal test port.
Scheme is further: be also provided with a decoded signal output circuit around described microprocessor chip, comprise operational amplifier, the D/A that the electrode input end of operational amplifier connects STM32 microprocessor chip by a capacitance exports, the electrode input end of operational amplifier connects a DC level translation circuit simultaneously, be transformed to the AC signal of 0 level symmetry by with the AC signal of 1.65V level symmetry, the negative input of operational amplifier and the output terminal short circuit of operational amplifier, the output signal of D/A drives through operational amplifier and exports at a decoded signal test port after level translation.
Scheme is further: described bandwidth limitation circuit comprises an integrated chip TP3057 and operational amplifier that is used as wave filter, the negative input of operational amplifier and output terminal short circuit, the electrode input end of operational amplifier connects the output terminal of TP3057 chip by an electric capacity, the electrode input end of operational amplifier connects a DC level translation circuit simultaneously, and the simulating signal after band limit drives through operational amplifier and exports from the output terminal of operational amplifier after level translation.The output of operational amplifier is connected to the A/D conversion input interface of microprocessor chip, DC level translation circuit makes the output signal of operational amplifier from being transformed to the AC signal of 1.65V level symmetry with the AC signal of 0 level symmetry, 1.65V carries out A/D as STM32 microprocessor and converts direct current supply, and described band limited audio signals test port is connected to the output terminal of TP3057 chip by a resistance.
Scheme is further: described microprocessor chip is also provided with connecting oscillographic PCM sampling pulse wave form output port and coding waveforms output interface.
The invention has the beneficial effects as follows: achieve on one screen countershaft simultaneous display analog signal waveform, sampling time, sampled signal, quantized value, binary coding code character simultaneously at any time, solve conventional P CM pulse code modulation (PCM) experiment oscillograph and directly can not show numerical value, as the problem of quantized value, scale-of-two code character, simulating signal and sampling pulse are under the same clock source of STM32 microprocessor controls simultaneously, the sampling frequency of STM32 microprocessor A/D change-over circuit can be set to the integral multiple relation of PCM sampling frequency, the analog signal waveform that guarantee liquid crystal shows and sampling pulse position are fixed, i.e. sampling pulse relative with correspondence position on a timeline in simulating signal fixing (synchronously), thus accurately determine the scale-of-two code character after encoding, solving conventional P CM pulse code modulation (PCM) tests because sampling pulse in experimental system and simulating signal are under different clock sources controls, can not ensure that the sample position of sampling pulse in simulating signal is relatively fixing, cause simulating signal through sampling, the unascertainable problem of lowest order code element of the scale-of-two code character quantized and obtain after coding.
Meanwhile, analog signal waveform, sampling time on time shaft, quantized value, a scale-of-two code character simultaneously synchronous screen display is shown, accurately can demonstrate sampled signal and the corresponding relation of simulating signal on time and phase place, accurately demonstrate the quantized value size corresponding to a certain sampling time, accurately demonstrate the scale-of-two code character that this moment quantized value is corresponding, can the complete procedure of clear observation analog signal figure process by student of the present invention in teaching, can observatory control signal waveform intuitively, sampling time on time shaft, sampled signal, quantized value, scale-of-two code character, can directly according to shown analog signal waveform, sampling time on time shaft, quantized value, at phase place and corresponding relation numerically between scale-of-two code character, analyze PCM pulse code modulation (PCM) principle and process, contribute to the understanding of student to knowwhy, invent owing to no longer needing 4 oscilloscope channels simultaneously, present invention saves loaded down with trivial details complex operations, time spent by debug process.
Meanwhile, tackle above-mentioned output signal, go back synchronism output coding waveforms, observed by oscillograph, be convenient to liquid crystal on show scale-of-two code character contrast; Synchronism output decoded signal, is observed by oscillograph, and comparison band limit audio analog signals, analyzes and quantize error size.
Below in conjunction with drawings and Examples, the present invention is described in detail.
Accompanying drawing explanation
Fig. 1 is classic method system schematic;
Fig. 2 is the figure of analog signal waveform of the present invention, sampling time, sampled signal, quantized value, binary coding code character simultaneous display;
Fig. 3 is the figure of sampling pulse of the present invention, coding waveforms display;
Fig. 4 is present system schematic diagram;
Fig. 5 is decoding output circuit schematic diagram of the present invention;
Fig. 6 is bandwidth limitation circuit schematic diagram of the present invention.
Embodiment
Fig. 2 illustrates traditional PCM pulse code modulation (PCM) principle and resolves experimental technique, the experiment of conventional P CM pulse code modulation (PCM) is that the experiment module circuit consisted of special coding and decoding chip realizes, and the signal that student can observe has input simulating signal, 8KHZ sampling pulse, encoded clock, coded signal.Just need 4 oscilloscope channels to observe above-mentioned 4 signals as PCM pulse code modulation (PCM) principle will be analyzed preferably simultaneously, only in this way just can observe the corresponding position in simulating signal of sampling time, corresponding relation between code rate and coding waveforms three, because sampling pulse in experimental system and simulating signal are under different clock sources controls, can not ensure that the sample position of sampling pulse in simulating signal is relatively fixing, cause simulating signal through sampling, the lowest order code element of the scale-of-two code character quantizing and obtain after coding be can not determine, according to the signal of oscilloscope, student can not obtain the scale-of-two code character determined, simultaneously because oscillograph can only display waveform, directly can not show numerical value, as quantized value and binary code, student also needs to restrain coding schedule to analyze the relation between quantized value and scale-of-two code character by A rule or U, reach the object understood and grasp PCM pulse code modulation (PCM) principle, so do not observe quantized value and scale-of-two code character intuitively by the experiment of conventional P CM pulse code modulation (PCM), intuitively can not reflect sampled signal, quantized value, relation between scale-of-two code character three, therefore conventional P CM pulse code modulation (PCM) experimental technique cannot show cataloged procedure, not obvious to the help of student's understanding and grasp PCM pulse code modulation (PCM) principle.
Nonetheless, the oscillograph completing above-mentioned experiment must be 4 oscilloscope channels, because watch 4 signal waveforms with two dual channel oscilloscopes, 4 signals cannot be observed at phase place and temporal corresponding relation, but the oscillograph that Scientific Research in University Laboratory is equipped with at present is generally dual channel oscilloscope or single channel oscillograph, because the relative complicated operation of 4 oscilloscope channel, debug process expends time in.
Embodiment 1:
In order to effectively solve conventional P CM pulse code modulation (PCM) experimental technique and circuit Problems existing, the present embodiment resolves experimental technique based on the PCM pulse code modulation (PCM) principle of STM32 microprocessor, comprises and input simulating signal is carried out to band limit, sampling, quantized and coded treatment; Described method is that sampling time on use STM32 microprocessor outputting analog signal waveform, time shaft, sampled signal, quantized value, binary coding group simultaneous display are in a liquid crystal display.
As shown in Figure 2, in embodiment: the processing procedure of described simultaneous display is:
The first step: set up a level of synchronization axle 1 on a liquid crystal display, described transverse axis is the time shaft based on described processor working frequency;
Second step: the A/D change-over circuit using microprocessor, samples to input simulating signal with the A/D sampling frequency of 64KHZ, and demonstrate the envelope of sampled signal in described liquid crystal display, form the input analog signal waveform 2 of corresponding time shaft;
3rd step: according to the PCM sampling frequency of PCM pulse code modulation (PCM) rule, microprocessor carries out PCM sampling to described simulating signal, described analog signal waveform is made PCM sampling time mark 3, PCM sampled signal 4 simultaneous display the below that sampling time marks or above.
4th step: microprocessor quantizes described PCM sampled signal, quantized value 5 simultaneous display corresponding to each PCM sampled signal the below that sampling time marks or above.
5th step: microprocessor carries out binary coding 6 to described quantized value, and by scale-of-two code character simultaneous display corresponding for each quantized value the below that sampling time marks or above.
In embodiment: described method comprises the step of Signal aspects debugging further, comprising:
The first step a: computing machine is connected STM32 microprocessor chip by an ARM emulator;
Second step: write operation one on computers and described input simulating signal is carried out being with limit, sampling, to quantize and coded treatment, simultaneous display is in the program of a liquid crystal display;
3rd step: carry out program function simulation by ARM emulator, simultaneous computer is debugged described program, is entered by download program in STM32 microprocessor chip after having debugged;
4th step: ARM emulator and computing machine are departed from STM32 microprocessor chip, STM32 microprocessor chip independent operating.
In embodiment: described pcm encoder modulation sampling frequency is 8KHZ.
In embodiment: described binary coding mode is that the A of 8 restrains 13 broken line codings, it is a kind of standard audio coded system, its method is that the span of audio analog signals amplitude is divided into 256 quantized levels, span by simulating signal amplitude is divided into 16 nonuniform quantiza intervals (16 large paragraph), each paragraph is divided into 16 uniform quantization intervals (16 segment) again, thus each quantized value is with being eight-digit binary number coded representation.
The code word arrangement that eight A restrain 13 broken lines codings is divided into three parts, and the first bit word is polar code, represents the positive and negative polarity of simulating signal with 1 and 0 respectively.The second to the four bit word is paragraph code, represents that the absolute value of signal quantization value is in which paragraph of 8 uneven large section, represents the initial level value of 8 paragraphs.In each large section, be divided into again 16 segments, the initial level numerical value in 16 segments represents with the five to the eight-level code, the five to the eight the four bit code section of being called ISNs.
The 12 figure place weighted-voltage D/A converters that STM32 in embodiment carries, extraction simulating signal instant amplitude value can be quantized into 4096 values, the scope of corresponding quantization level is 0 ~ 4096
,deduct 2048 by the subtraction circuit in microprocessor, the range of quantization level is-2048 ~ 2048
,just in time correspond to the scope that A restrains the quantization level of 13 broken line codings, if quantized value is at-2048 ~ 0 level range, A is adopted to restrain 13 broken line codings, then think that first polar code is 0, if quantized value is at 0 ~ 2048 level range, then think that first polar code is 1, microprocessor restrains 13 broken line coding schedules draw binary coding code character corresponding to each quantized value by looking into A.
Use the A/D change-over circuit of microprocessor, with the A/D sampling frequency of 64KHZ, input simulating signal is sampled, and demonstrate the envelope of sampled signal in described liquid crystal display, form the analog signal waveform of corresponding time shaft;
The instant amplitude value of the extraction input simulating signal in embodiment is completed by the built-in A/D change-over circuit of STM32, and demonstrate the envelope of sampled signal in described liquid crystal display, forms the analog signal waveform of corresponding time shaft; For ease of showing the envelope of level and smooth sampled signal on liquid crystal, A/D sampling frequency is decided to be 64KHZ, and conventional pcm encoder modulation sampling frequency is 8KHZ, therefore by with the A/D sampling frequency of 64KHZ, input simulating signal carry out sampling every 8 sample values of sample value signal of gained is compiled to a subcategory number and just can be met pcm encoder and modulate requirement.
Coding is the process quantization level that each sample value is got being transformed into one group of binary code, and A restrains 13 broken lines codings in this way, and microprocessor restrains 13 broken line coding schedules draw binary coding code character corresponding to each quantized value by looking into A.
In order to the corresponding relation further comprehensively between all signals of study PCM pulse code modulation (PCM) process, in embodiment: the sampling time of described method on outputting analog signal waveform, time shaft, sampled signal, quantized value, binary coding code character simultaneous display are while a liquid crystal display, as shown in Figure 3, described method comprises further: tackle above-mentioned output signal, also synchronism output coding waveforms 20 and PCM sampling pulse waveform 21, described waveform is observed for oscillograph, with the scale-of-two code character comparison that shows on liquid crystal.Synchronism output decoded signal,
Observed by oscillograph, comparison band limit audio analog signals, analyzes and quantizes error size.
Embodiment 2:
A kind of PCM pulse code modulation (PCM) principle based on STM32 microprocessor resolves experimental system, it is the system realizing method described in embodiment 1, as shown in Figure 4, comprising a STM32 microprocessor chip 7, is the STM32F103 high speed microprocessor chip of Cortex-M3 core.A frequency range is provided with at the bandwidth limitation circuit 8 of 300HZ-3400HZ and digital lcd 9 around described microprocessor chip; The input end of described bandwidth limitation circuit connects audio analog signals Acquisition Circuit 10, the output terminal of described bandwidth limitation circuit connects the A/D(analog-to-digital of microprocessor chip) input interface, liquid crystal display connects the DOL Data Output Line of described microprocessor chip by LCD interface circuit 11, and the output of described bandwidth limitation circuit is provided with a band limited audio signals test port 12.
Sampling time in embodiment on analog signal waveform, time shaft, sampled signal, quantized value, binary coding code character are connected to the display of color touch LCDs by LCD interface circuit module, the corresponding microprocessor chip data line of 16 position datawires of interface module.
In embodiment: be also provided with a decoded signal output circuit 13 around described microprocessor chip, the input end of described decoded signal output circuit connects the D/A(numeral revolving die plan of microprocessor chip) output interface, the output terminal of decoded signal output circuit is a decoded signal test port 14, decoded signal test port and described band limited audio signals test port are for being connected two lane testing inputs of a dual channel oscilloscope, to audio analog signals and decoded signal display comparison, analyze and quantize error size, physical circuit is as shown in Figure 5: quantize output circuit and comprise operational amplifier 15, the electrode input end of operational amplifier connects the D/A output interface of STM32 by a capacitance C1, the electrode input end of operational amplifier connects a DC level translation circuit be made up of resistance R1 and R2 dividing potential drop simultaneously, be transformed to the AC signal of 0 level symmetry by with the AC signal of 1.65V level symmetry, the negative input of operational amplifier and output terminal short circuit, the output signal of D/A drives through operational amplifier and exports at a decoded signal test port 14 after level translation, decoded signal test port and described band limited audio signals test port, for being connected two lane testing inputs of a dual channel oscilloscope, comparing the difference between input audio analog signals and decoded signal, analyze and quantize error size.
In embodiment: as shown in Figure 6, it is TP305716 integrated chip and an operational amplifier 17 that described bandwidth limitation circuit comprises a model being used as wave filter, the negative input of operational amplifier and output terminal short circuit, the electrode input end of operational amplifier connects the output terminal of TP3057 chip by an electric capacity C2, the electrode input end of operational amplifier connects a dividing potential drop DC level translation circuit be made up of resistance R3 and R4 simultaneously, namely the mid point of divider resistance R3 and R4 is connected to, simulating signal after band limit drives through operational amplifier and exports from the output terminal of operational amplifier after level translation.The output of operational amplifier is connected to the A/D conversion input interface of microprocessor chip, DC level translation circuit makes the output signal of operational amplifier from being transformed to the AC signal of 1.65V level symmetry with the AC signal of 0 level symmetry, and described audio test signal port is connected to the output terminal of TP3057 chip by a resistance.
In order to can the signal intensity of multianalysis processing procedure, in embodiment: described microprocessor chip is also provided with connecting oscillographic PCM sampling pulse wave form output port one 8 and coding waveforms output interface 19.
Claims (9)
1. the PCM pulse code modulation (PCM) principle based on microprocessor resolves experimental technique, comprises and input simulating signal is carried out to band limit, sampling, quantized and coded treatment; It is characterized in that, described method is that sampling time on use STM32 microprocessor outputting analog signal waveform, time shaft, sampled signal, quantized value, binary coding group simultaneous display are in a liquid crystal display;
The processing procedure of described simultaneous display is:
The first step: set up a level of synchronization axle on a liquid crystal display, described transverse axis is the time shaft based on described processor working frequency;
Second step: the A/D change-over circuit using microprocessor, samples to input simulating signal with the A/D sampling frequency of 64KHZ, and demonstrate the envelope of sampled signal in described liquid crystal display, form the input analog signal waveform of corresponding time shaft;
3rd step: according to the PCM sampling frequency of PCM pulse code modulation (PCM) rule, microprocessor carries out PCM sampling to described simulating signal, described analog signal waveform is made PCM sampling time mark, PCM sampled signal simultaneous display the below that sampling time marks or above;
4th step: microprocessor quantizes described PCM sampled signal, quantized value simultaneous display corresponding to each PCM sampled signal the below that sampling time marks or above;
5th step: microprocessor carries out binary coding to described quantized value, scale-of-two code character simultaneous display corresponding to each quantized value the below that sampling time marks or above.
2. experimental technique according to claim 1, is characterized in that, described method comprises the step of Signal aspects debugging further, comprising:
The first step a: computing machine is connected STM32 microprocessor chip by an ARM emulator;
Second step: write operation one on computers and described input simulating signal is carried out being with limit, sampling, to quantize and coded treatment, simultaneous display is in the program of a liquid crystal display;
3rd step: carry out program function simulation by ARM emulator, simultaneous computer is debugged described program, is entered by download program in STM32 microprocessor chip after having debugged;
4th step: ARM emulator and computing machine are departed from STM32 microprocessor chip, STM32 microprocessor chip independent operating.
3. experimental technique according to claim 1, is characterized in that, described PCM sampling frequency is 8KHZ.
4. experimental technique according to claim 1, is characterized in that, described binary coding mode is that the A of 8 restrains 13 broken line codings.
5. experimental technique according to claim 1, it is characterized in that, sampling time on outputting analog signal waveform, time shaft, sampled signal, quantized value, binary coding code character simultaneous display are while a liquid crystal display, described method comprises further: tackle above-mentioned output signal, also synchronism output coding waveforms and PCM sampling pulse waveform, described waveform is observed for oscillograph, with the scale-of-two code character comparison that shows on liquid crystal.
6. the PCM pulse code modulation (PCM) principle based on microprocessor resolves experimental system, comprise STM32 microprocessor chip, it is characterized in that, be provided with a frequency range at the bandwidth limitation circuit of 300HZ-3400HZ and digital lcd around described microprocessor chip; The input end of described bandwidth limitation circuit connects audio analog signals Acquisition Circuit, the output terminal of described bandwidth limitation circuit connects the A/D conversion input interface of microprocessor chip, liquid crystal display connects the DOL Data Output Line of described microprocessor chip by interface circuit, and the output of described bandwidth limitation circuit is provided with a band limit audio analog signals test port.
7. experimental system according to claim 6, it is characterized in that, a decoded signal output circuit is also provided with around described microprocessor chip, comprise operational amplifier, the electrode input end of operational amplifier connects the D/A output interface of STM32 microprocessor chip by a capacitance, the electrode input end of operational amplifier connects a DC level translation circuit simultaneously, be transformed to the AC signal of 0 level symmetry by with the AC signal of 1.65V level symmetry, the negative input of operational amplifier and the output terminal short circuit of operational amplifier, the output signal of D/A drives through operational amplifier and exports at a decoded signal test port after level translation.
8. experimental system according to claim 6, it is characterized in that, described bandwidth limitation circuit comprises an integrated chip TP3057 and operational amplifier that is used as wave filter, the negative input of operational amplifier and output terminal short circuit, the electrode input end of operational amplifier connects the output terminal of TP3057 chip by an electric capacity, the electrode input end of operational amplifier connects a DC level translation circuit simultaneously, and the simulating signal after band limit drives through operational amplifier and exports from the output terminal of operational amplifier after level translation; The output terminal of operational amplifier is connected to the A/D conversion input interface of microprocessor chip, DC level translation circuit makes the output signal of operational amplifier from being transformed to the AC signal of 1.65V level symmetry with the AC signal of 0 level symmetry, 1.65V carries out the direct current supply of A/D conversion as STM32 microprocessor, and described audio test signal port is connected to the output terminal of TP3057 chip by a resistance.
9. experimental system according to claim 6, is characterized in that, described microprocessor chip is also provided with connecting oscillographic PCM sampling pulse wave form output port and coding waveforms output interface.
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201177901Y (en) * | 2008-04-25 | 2009-01-07 | 桂林电子科技大学 | Experiment apparatus for modern communication principal teaching |
| CN201868009U (en) * | 2010-05-19 | 2011-06-15 | 北京化工大学 | FPGA (Field Programmable Gate Array) communication experiment device |
| CN103198734A (en) * | 2012-01-06 | 2013-07-10 | 苏州市职业大学 | Signal synchronization PCM coding and decoding experiment system |
| CN203520727U (en) * | 2013-11-02 | 2014-04-02 | 常州信息职业技术学院 | Portable STM32 one-chip microcomputer teaching experiment instrument |
| CN203659297U (en) * | 2013-11-20 | 2014-06-18 | 武汉大学 | Communication principle experiment box apparatus for teaching |
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