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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Automotive voice informer. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic devices The article describes a device that is capable of verbally reporting problems in the car both during parking and while driving in a voice (your or another person's). The device "interrogates" the sensors located in the most important units of the machine, and, based on the results of the survey, forms speech fragments that reflect the state of the controlled units. Automotive speech informants designed for sound notification of the operation of various sensors or, in other words, the state of vehicle systems, have been produced for a long time [1]. However, a relatively small number of controlled parameters, attachment to one or another specific car model, and a rather high price limit the wide distribution of these devices. Amateur radio developments of such informants are also known. At one time, there were attempts to apply delta modulation for speech synthesis [2; 3]. Such devices, although they save memory resources, but assembled from discrete elements, were very complex. The process of recording sound in ROM is also not easy. It was often more difficult to make a recording node than a reproducing one. At the same time, the growth in the amount of EPROM memory (electrical recording and "ultraviolet" erasure) and their reduction in cost make it possible to implement speech recording without resorting to complex coding and the use of specialized microcircuits. This, firstly, facilitates the subsequent digital-to-analog conversion and, secondly, simplifies both the software and hardware parts, and the process of recording sound in ROM. All you need is a microphone, a sound card, and a simple program that comes with the Windows operating system. The speech informant described here can be mounted on cars of domestic and foreign production. It is programmed with 22 words and phrases that have an independent semantic meaning. The scheme of the program is shown in fig. 1.
In the main components of the car, sensors are installed that generate alarms when triggered. The sensors are connected to a logical node connected to the microprocessor, which constantly interrogates the sensors and, upon recognition of one or another alarm signal, decides to play the corresponding warning phrase. How does a speech informant work? When the power is turned on (and also when the "Reset" button is pressed), a distinctive tone sounds, indicating that the system is turned on and operating normally. Next, the sensors of those nodes that are supposed to be checked before leaving the garage are interrogated. If one of the sensors generates an alarm, the informant says the word "Attention" followed by the appropriate phrase. In the event that after 30 seconds the position has not changed, the word "Repeat" sounds and the same message is played again. The phrase "Reverse" is intended for those who drive VAZ cars of models 2108 and 2109, in which the positions of first and reverse gears are nearby, and novice drivers often confuse them. The words "Differential Lock" and "Rear Axle Engaged" are addressed to owners of all-wheel drive vehicles with forced differential lock, and they sound at an interval of 30 seconds as long as these nodes are turned on. In the same mode, the phrase "Engine overheating" also sounds. The warning "Dimension on" is pronounced after a pause of 30 seconds only when they turned on during daylight hours. A pause is needed so that the system does not mistake the headlights of oncoming cars for the onset of dawn. Then follows the control of the engine. If it is off, the program returns to the beginning, and if it runs at excessively high speeds, the phrase "Emergency engine speed" sounds. Next, the oil pressure is measured, while the crankshaft speed should be more than 1500 min-1. After that, the program measures the onboard voltage and checks if the direction indicator is on. If it is turned on for more than 30 seconds, the word "Turn on" sounds. In the event that the indicator is turned off before the expiration of 30 s, and then turned on again, the countdown starts again. Further, the device determines in what position the car is - standing or moving. In the first case, the program returns to the beginning, and in the second, it starts polling the sensors for the doors, handbrake and seat belts. The corresponding phrases are heard twice with an interval of 30 seconds, but after the car stops and the doors are opened, they can be repeated. In the absence of a passenger, the sensor of his belt is not interrogated. During starter operation, the on-board voltage decreases, strong electromagnetic interference is generated, due to which a wide variety of false messages are possible that have nothing to do with reality. Therefore, when a signal is received to turn on the starter, the informant suspends the polling of the sensors. The phrase started up to the specified moment sounds to the end, after which all functions are blocked until the starter is turned off. The informer (see diagram in Fig. 2) consists of a DD1 microprocessor that controls the operation of all main components, DS1 program memory, DS2, DS3 sound memory, DD8-DD10 input ports, DD4 DAC, R35R36C14C15DA8 low-pass filter with a 3H DA9 amplifier and a line of input comparators on the op-amp DA1 - DA6 and DD5.1 - DD5.4.
A fuel level sensor in the tank, two engine temperature sensors and an oil pressure sensor, respectively, are connected to the input of comparators DA1 - DA4. Resistors R10, R14, R17, R20 provide the electrical hysteresis of the op-amp and increase their noise immunity. An exemplary voltage is removed from the zener diode VD4 to set the threshold for the operation of the comparators. Fluid level sensors - brake and washer - and a light sensor are connected to the input ports through Schmitt triggers DD5.1-DD5.4. On elements DD6.3, DD6.2, DD7.1 - DD7.4 address encoders of input ports are assembled. The inputs of the ports DD8 and DD10 through the resistors of the DR1, DR3 assemblies are connected to the positive power wire, which, together with the protective diodes VD6-VD16, allows you to protect the ports from getting voltage greater than 5 V. The DD9 port is also protected at the input by resistive dividers R28 - R33, DR2. The microprocessor DD1 extracts with a frequency of 8 kHz from the ROM DS2, DS3 a digitized signal of the audio message and transmits it to the outputs of the audio register DD3. DAC DD4 converts the signal into analog form. After this conversion, the signal is heavily "polluted" by switching noise. A second-order low-pass filter with a cutoff frequency of 4 kHz eliminates this interference. Amplifier 3H DA9 in the standard inclusion is loaded with a dynamic head with a resistance of 8 ohms. If the car is equipped with audio equipment, you can use its speakers. For this case, a transistor VT1 and a relay K1 are provided, the contacts of which switch the output circuits. In normal mode, the on-board radio (or radio) is connected by relay contacts to its loudspeaker. If any deviation from the norm occurs on board, a high level occurs at the TXD output of the microprocessor, the transistor VT1 opens, relay K1 is activated and its contacts switch the loudspeaker from the receiver output to the informer output. After the end of the message, the radio plays again. Sound information, i.e. the instantaneous values of the amplitude of the sound signal measured at a certain frequency, is recorded in the ROM DS2, DS3. In order to losslessly digitize an audio signal, the sampling frequency must be at least twice the maximum signal frequency (including harmonics). If the sampling frequency is chosen equal to 8 kHz, then the maximum signal spectrum will be limited to 4 kHz, which, with eight-bit amplitude sampling, approximately corresponds in sound quality to what we hear over a telephone line. Information is recorded in memory using a computer with a sound card. Having recorded and processed the sound on a computer, having selected the timbre and sound, they record the sound in ROM. Then a scanning counter with a simple start-stop logical device is connected to the address inputs and either a doorbell, or a children's toy, or an alarm clock is received. In the simplest case, if neither tone control nor special effects are needed, you can use the Sound Recorder program (in the Russian version "phonograph"), which is included as standard with Windows95. But it is better to use more convenient special programs, for example, Goldwave or Sound Forge. Before you start recording an audio signal, you must enable PCM modulation (Pulse Code Modulation - pulse-code modulation) - a standard way to digitally encode a signal using a sequence of absolute amplitude values. There are signed (signed) and unsigned (unsigned) representations. With a sign signal, the signal is bipolar and the readings can take values from -N to +N, where N is the maximum possible amplitude. Unsigned is a unipolar representation where the counts go from zero to N. In our case, it is more convenient to use the unsigned representation. Then, in the absence of a signal, the number 80Н will be written to the memory cells. If the signal envelope goes down, numbers less than 80N will be recorded, and if it goes up - more than 80N. Then you need to select the audio file format. Currently, the Microsoft RIFF (Resource Interchange File Format) Wave (WAV) format has become the de facto standard. It contains the digitized sound and file header (mono/stereo, 8/16 bits, sample rate, file length) and is supported by all sound processing programs without exception. There is, in addition, the RAW format, which is not supported by the Sound Recorder program, but we just need it. RAW is a single-channel "pure digitization" format that does not contain a header. It is easy to get RAW format from WAV. Selecting a sampling rate of 8 kHz, mono, PCM modulation, bit depth of 8 bits, we record the sound to a file in WAV format. Then, with any text editor (it can even be built into Norton Commander), we delete the file header up to and including the word "data" and the copyrights at the end of the file. If you use more advanced programs than Sound Recorder, and they support the RAW format, then the desired file will be obtained automatically. It remains only to write it to ROM as is. As already mentioned, to suppress switching noise, a low-pass filter is included after the DAC. Due to its imperfection, it cuts off not only switching noise, but also high-frequency signal components. To compensate for these losses, the signal should be slightly corrected during recording - "raise" these components with the tone control. So, having set the necessary options in your sound processing program, you have written some phrase to a file with the WAV extension. Removed "tails" at the beginning and end of the file - slightly reduced the file size. Then you need to normalize the sound in amplitude, that is, bring all words and phrases to the same volume. You can write down individual words, and then make up sentences from them, but at the same time, rises and falls that are imperceptible to the ear in the final phrase will be absent, and it will look artificial. Therefore, if you need one word, it is better to write down the whole phrase, and only then cut out the word you need from it. When dividing a word into parts, for example, "emergency" and "emergency", it is better to divide it on the suffix "n", leaving a little of it both in the root part and at the end. So the "glue" will be less noticeable. If your program has the "Soft attack" option, then it's better to turn it on - it will remove the "glue" clicks. After processing the file in this way and listening to it, you can convert it to RAW format and burn it to disk. To facilitate further work at the beginning of the file with any text editor, you can add a small heading indicating the sound recorded in this file, for example, "attention" or "emergency". After all the words have been processed and written, they need to be combined into two large files suitable for writing to the DS2 and DS3 ROMs. This can be done under DOS with the "copy" command with the /b binary switch. For example, like this: Copy /b <name of the final file>. Here is the resulting final file of 64 KB in size is written to the ROM. If your file is larger than 65535 bytes, then the size of its constituent files will have to be reduced a bit by pronouncing the words faster or cutting the "tails" more. After that, you need to determine the resulting absolute addresses of the beginnings and ends of words in the ROM. It is convenient to do this with Norton Commander or Windows Commander, which are available on almost every computer. Open the file for reading, set the program to view hexadecimal numbers, and look for the titles you previously assigned to sound files, writing down the resulting addresses of the beginnings and ends of words. The microprocessor of the informant, having received the sender's signal about the occurrence of a problem and processing it according to the appropriate algorithm, decides to play a warning phrase. To do this, the microprocessor accesses the memory array, which contains the absolute addresses of the beginning and end of words or parts of words. A fragment of the C program that forms these arrays for the DS2 and DS3 ROMs is presented in Table. 1. Having received information about the absolute addresses and the ROM number, the microprocessor refers to a subroutine that reads the desired memory cells of the audio ROM and transfers the resulting value to the digital-to-analog converter.
When generating a sound ROM file, keep in mind that the sequence of words and parts of words must be kept the same as in the fragment shown, but the addresses are likely to be different. In order not to recompile the program for these addresses again, they can be corrected in the program dump "manually". After compiling the program, the Rom0 array is located in memory from the address 0043Н to 008ЕH, the Rom1 array - from the address 008FH to 00С2Н, and the two-byte addresses of the beginning and end of words are written in the order of high byte - low byte (Table 2). To process a program dump, you can use a well-known program HDB or built-in programmer editor.
The microprocessor selects the desired ROM by driving low on port pins P0 or P1. During the development of the device, it turned out that the microprocessor had unused control pins, for example, RXD, which makes it possible to add one more phrase to the above phrases. In the author's version, these are the words - "Differential Lock", which are repeated at intervals of 30 seconds as long as there is a low level on pin 11 of the X1 input connector. These words are recorded in an additional memory chip 27128, soldered on top of the main ROM with all its pins, except for 22 (it is not shown in the circuit diagram). Pin 22 is connected by a separate conductor to the RXD pin of the microprocessor. The addresses of this ROM are in cells 00C3H - 00C6H. If you are not the owner of "Niva" or "Jeer", you can not install additional ROM, and leave pin 11 of connector X1 free. Using the program scheme (Fig. 1) and the sound recording technique described above, you can write any other phrase into this additional memory chip, for example, "Trunk open" or "Security on", and turn it on with the corresponding closed contacts. The circuit diagram (Fig. 2) shows the active signal levels (to the left of the diodes VD6 - VD23 and resistors R28 - R33), which include one or another phrase. Most automotive sensors are designed in such a way that, with any deviation from the norm, open contacts close the circuit to the case. If the sensors installed on your car generate signals of a different level, they will have to be inverted (a free DD6.4 inverter is useful here). The inputs from the turn signal relay, speedometer and breaker respond to a negative voltage drop. The author considers it necessary to note that he developed the device in such a way that the informant could be installed on almost any car without modification. For this reason, the device has some redundancy. On cars of some brands, an emergency oil level sensor is already provided. If your machine does not have such a sensor, it is not difficult to make it yourself. It is a blind tubular rack 1 (Fig. 3) with a mounting flange at the bottom, made of non-magnetic metal - brass. Inside the tube, a miniature reed switch 2 is inserted and fixed with a heat-resistant silicone sealant.
A float 3 is put on the outside of the tube, soldered from thin sheet brass; it has the ability to move freely along the rack. A tubular magnet 4 is fixed on the central tube of the float with drops of solder, the poles of which are located at its ends. The rack assembly with the float is inserted into the hole in the bottom of the engine crankcase 5 from below and is securely fixed in one way or another. The conductors from the reed switch are protected from the outside by a strong tube 6, the end of which is clamped with a rubber sleeve in the mounting flange of the rack 1. On fig. 3 the device of the emergency oil level sensor is shown schematically. The practical design and dimensions of the device must be adapted to the specific installation conditions. The main requirement is to ensure that there is no oil leakage even if the crankcase is partially deformed. To calibrate the sensor mounted on the machine, it is installed on a horizontal platform, oil is poured into the engine to the minimum required level and the reed switch in the rack is slowly moved up until it closes. In this position, the reed switch is fixed with sealant. If your car already has brake fluid level float sensors, they can be connected to the left output of diodes VD2 and VD3 according to the scheme, disconnecting them from the output of elements DD5.2 and DD5.3. (See Fig. 2). In the absence of such sensors, on "Moskvich-2141", for example, you can make the simplest home-made ones. A brass rod is fixed in the plastic lid of the brake fluid cup so that its lower end does not reach the bottom by 2 ... 3 cm; the top one is connected to the corresponding pin of the X1 input connector. The operation of the sensor is based on the fact that ethylene glycol brake fluids "Rosa", "Neva" and "Tom" have a noticeable electrical conductivity. The second electrode is the metal case of the brake master cylinder. When there is enough liquid, the input of Schmitt triggers DD5.2, DD5.3 is low. In the event of an emergency level of brake fluid, the rods are in the air, the low level at the input of the Schmitt triggers changes to a high one. Resistors R4 and R5 (see Fig. 2) may need to be selected for a clearer operation. The sensor for the minimum level of liquid washing the windshield is also arranged, the only difference is that there are two rods in it and one of them is connected to the common wire of the system (to the body). Since the conductivity of the washer fluid is greater than that of the brake fluid, resistor R6 has a much lower resistance. The sensor of the closed air damper of the carburetor (option "Sucking") is used ready from the "Zhiguli", otherwise it will be necessary to install a suitable limit switch on the carburetor. Before continuing the story about the work of the speech informant, we ask you to correct the text of the "litter" command in the penultimate paragraph of the first part of the article published in the May issue of the journal. The command text should be like this: Copy/b<name of the first file>+<name of the second file>+...+<name of the nth file><space><name of the final file The antifreeze level sensor is a standard float, in which the output closes to the body when the coolant level drops beyond the permissible limit. As a device that indicates the burnout of signal lamps (direction indicator, side lights and brake light), you can use a ready-made relay for monitoring the health of lamps of a VAZ-2109 car. In the author's version of the informant, a three-channel node, described in [4], works. A low-resistance resistor is connected in series with each controlled circuit, the voltage drop across which determines the serviceability of the lamps. It is only required to swap the inverting and non-inverting inputs of the op-amp so that when the lamp burns out, not a low, but a high level appears at its output, which will then highlight the adder on diodes and a resistor. A fragment of the diagram of this node is shown in fig. 4.
The advantage of the device [4] is that it makes it very easy to adjust the response threshold (with a variable resistor). Due to the high sensitivity, the op-amp can even catch the burnout of the lamp of the side turn signal repeater with a power of only 2 watts. In a device with reed switches, the response threshold can only be adjusted by changing the number of turns of their windings, and the sensitivity is worse. The minimum fuel level comparator DA1 (see Fig. 2) receives a signal from a rheostatic sensor installed in the tank. If your car does not have a rheostatic, but a contact fuel level sensor, you can use the signal from it. The OU in this case will work as an inverter. The same applies to emergency oil pressure and emergency temperature sensors. The program provides protection against "bounce" impulses of the contacts of such sensors, but it is still better to use rheostatic sensors, since all mechanical contact sensors have a large error and unregulated response thresholds. The rheostatic sensor allows you to set any threshold. Having disconnected the sensor on the car and connected a variable resistor instead, set the arrow of the gas gauge (thermometer or pressure gauge) to any desired division. Then, by turning the knobs of the resistors (R13, R16, R19), adjust the alert system thresholds. Do not forget that the processor polls the oil pressure sensor only at an engine speed of more than 1200 min-1. To prevent false alarms from splashing fuel and washer fluid in the tanks, the time constant of these meters is large - about 3 s - and is implemented in software. Thus, all input comparators are intended only for rheostatic sensors and cannot work with pulsed thermobimetallic sensors. If your car is no longer new, then before you start adjusting the operation of the temperature comparators, it is advisable to check the performance of the temperature sensor, for example, in boiling water. The fact is that copper-manganese thermistors, usually used for these purposes on domestic cars, significantly change their resistance over time. If the temperature sensor is in boiling water, and the thermometer needle does not show 100 ° C, you must either replace the temperature sensor with a new one, or rearrange the arrow on the pointer axis to the correct position. Connecting an additional resistor is not recommended, as it may violate the temperature correction of the ratiometric indicator [5]. The onboard voltage control unit has no special features. By connecting the informant to an adjustable power source, resistors R22 and R27 set the desired levels. Let me remind you that the processor checks the supply voltage only when the engine is running. If you decide to adjust the comparators DA5, DA6 in laboratory conditions, you need to simulate the operation of the engine by applying a pulse signal with a frequency of 10 ... 200 Hz to the XB14 pin of the X1 connector. With the help of a generator, it is advisable to check the operation of the emergency speed warning unit so as not to torment the engine with prohibitive modes. The turn signal is taken from the indicator lamp on the dashboard. By the way, the duration of the included direction indicator is also checked with the engine running. Information about the engine speed comes from the Hall sensor of the interrupter. Since such sensors do not have "bounce", then the program does not provide protection against it. If your car has a classic contact ignition system, then you can protect yourself from "bounce" impulses by hardware (the magazine wrote about this more than once; in particular, the input part of the electronic tachometer [6] is suitable). As noted above, during the operation of the starter, the program is blocked in order to avoid failures. The signal to turn on the starter is removed from the winding of its executive solenoid (otherwise called the retractor relay). To dampen the back EMF of the solenoid winding in the immediate vicinity of it, it is necessary to solder a protective diode with the cathode to the positive terminal in parallel with the winding. For this purpose, it is convenient to use medium power diodes with an anode on the case, for example, KD208A. Such a measure, by the way, will not only reduce the level of electromagnetic interference, but also significantly extend the life of the contacts of the intermediate relay or ignition switch. Instead of a diode, you can also use a medium power zener diode, for example, D815E or D815Zh. The zener diode at the same time will "cut off" the positive voltage spikes at a safe level. In general, if there are any other relays on your car whose windings are not shunted with spark-quenching diodes, you should do this. The light sensor is a photoresistor SFZ-4, mounted so that it does not get direct light from the headlights of oncoming cars. It is convenient to set the sensor threshold at dusk, when you consider it timely to turn on the parking lights or low beam headlights. The threshold is adjusted by resistor R7. Please note that the voice notification of the side lights on is delayed, that is, by turning the resistor R7 slider at a small angle, you have to wait 30 seconds for a reaction to this. It is more convenient and faster to adjust the node by connecting a voltmeter to the output of the Schmitt trigger DD5.1. Door sensors are switches whose contacts close when the door is opened. They must be adjusted so that they open when the door lock is closed by two clicks. It is permissible to use the switches on the doors that control the lamps at the end of the doors. Miniature switches are mounted on the seat belt buckles, which are interrogated by the processor only when the car is moving. Their contacts open when the belt tongue is inserted into the lock. The driver's belt sensor is connected directly to the input port, because if the car is moving, then the driver is in place. The passenger seat belt sensor is connected in series with the sensor in the passenger seat. Thus, the passenger's belt sensor is polled only when the passenger's presence sensor has been triggered. The fact that the car is moving is reported to the processor by a sensor mounted on the speedometer. Most automotive mechanical speedometers contain a rotating magnet. If a coil on an open magnetic circuit is brought close to it, an EMF will be induced in it with a frequency equal to twice the frequency of rotation of the magnet. The role of the coil in the sensor is played by the winding from the RES15 relay; passport RS4.591.001 (or RS4.591.008). Winding resistance - 2,2 kOhm. The body, contact system and armature are removed from the relay. The coil is placed on the side of the non-magnetic insert of the speedometer so that the open side of the magnetic circuit is facing the rotating magnet. The schematic diagram of the sensor is shown in fig. 5.
It is convenient to solder the coil into a small board, on which to place the op amp with related parts, and the board, in turn, to be mounted on a bracket. Bending the bracket, find the optimal position of the sensor. Instead of a homemade one, you can use a ready-made speedometer sensor from a trip computer. The scheme for connecting sensors to the vehicle equipment system and to connector X1 of the speech informant is shown in fig. 6.
The working conditions of electronic equipment in a car are very difficult. Since for most radio amateurs special-purpose components are inaccessible and you have to assemble your products from what is at hand, you should, if possible, facilitate the work of a voice informant. In particular, the device must be placed in the cabin, where there are less temperature differences, and fastened through rubber shock-absorbing bushings. The casing must be durable and well protect the device from dust and moisture. The current consumed by the informant is about 300 mA, so a relatively small heat sink is sufficient for the DA7 stabilizer. If the casing is metal, it can also be used as a heat sink for DA7 and DA9 microcircuits. If the logic element DD6.4 remains free, do not forget to "ground" its inputs. It is known that there is a lot of electromagnetic interference in the electrical system of the car and in its on-board network. This forces the speech informant to be fed through a protective filter. You can use a ready-made filter from a disused car radio or buy a car filter made as a separate device. It is easy to make a homemade P-filter. It consists of a choke with an inductance of about 300 μH and two oxide capacitors with a capacity of 200 ... 500 μF. A very responsible approach should be taken to the choice of details for a speech informant. Microcircuits in a plastic case should be preferred to metal-ceramic and ceramic ones. When choosing capacitors, pay attention to their temperature capabilities. So, oxide capacitors K50-16 are operational at a temperature not lower than -20°C. In the case when you do not provide for further modernization of the device, it is better to mount memory chips and a microprocessor on a board without panels. If you cannot do without panels, I do not recommend using domestic SNPs; much more reliable than imported ones with round spring contacts. Massive parts must be additionally fixed to the board with wire clamps. A drawing of the printed circuit board of the informer is shown in fig. 7. Its dimensions are 172x72 mm. It is made of fiberglass 2 mm thick, foil-coated on both sides. The device uses tuning resistors SPZ-19a-0,5 (R7) and SP5-28B (the rest). Oxide capacitors - K52-1B, C5 - K53-19; the rest of the capacitors - any ceramic (KM5, KM6). Connector X1 - SNP53-60. Relay K1 - RES60, passport RS4.569.435-02 (or RS4.569.435-07).
A view of one of the variants of the speech informant with the casing removed is shown in fig. 8.
When assembling the informant, it is better to install the parts on the board not all at once, but in groups. The fact is that in microprocessor systems of this level of complexity, many elements are connected to the information and address lines. By soldering them all at once and discovering that the system is not working, you will greatly complicate your search for a faulty element. You can start with a 3H amplifier with a preliminary low-pass filter on the op-amp DA8. To the left according to the diagram in Fig. 2 to the output of the resistor R35 through a decoupling capacitor, the output of the LF generator is connected, and the dynamic head is connected to the common point of the capacitors C17 and C18. After adjusting the 3H amplifier, check the frequency response of the filter. Up to a frequency of 3,7 kHz, its frequency response should be horizontal, and then fall off with a steepness of 12 dB per decade. Then the DD1 - DD4, DD6 chips and the panel for DS1 are soldered. Without inserting the ROM with the program into the panel, they check the operation of the processor clock generator, as well as the presence of PSEN and ALE signals. The P2 port pins must be full swing signals. If the amplitude on any output is small or completely absent, check the corresponding line for a short circuit with neighboring ones. When you press the SB1 "Reset" button and hold it down, all ports should go into the third high-impedance state. Especially to facilitate the establishment of the informant, the test program was written. It is presented in Table. 3. The volume of the program is less than a kilobyte, so it will fit in the K573RF2 or K573RF5 ROM. But the panel for DS1 is twenty-eight-pin, while K573RF2 has 24 pins. In this case, for the programmed K573RF2 ROM, pin 21 is bent to the side so that it does not enter the panel socket, and connected through a resistor with a resistance of 1 ... 2 kOhm to pin 24. The microcircuit is inserted into the panel for DS1 with a shift of two pins - pin 1 of the ROM should go into socket 3 of the panel.
The test program is written in such a way that when the power is turned on, codes from 4 to 0 begin to arrive at the control inputs of the DD225 DAC, and at its output you can see a sawtooth signal with an amplitude of about half a volt with even and identical steps. If the steps are not the same, there are problems with any bit of the DD4 or DD3 chip. If there is no signal at all, most likely, either the DD1 microprocessor or the DD2, DD3 registers are to blame, since a working processor, if its PSEN and ALE signals are in order, is simply obliged to read the command from the ROM and execute it. Having achieved a good shape of the sawtooth voltage at the output of the DAC, they proceed to the most pleasant thing - the extraction of meaningful sounds. To do this, soldering the elements DR4, R43, R44, VD24 into place and inserting the DS2, DS3 memory chips into their panels, briefly close the P1.3 output of the microprocessor to a common wire. The device starts to play all the words recorded in the DS2 ROM, after which the sawtooth voltage appears again at the DAC output. If what you hear suits you, the test ROM is changed to a working one. Next, solder one by one additional ports DD8-DD10 and check the operation of the main working program. It is presented as a dump and nothing can be changed in it, except for an array of word addresses. By typing this dump in a text editor and flashing the ROM, you can stop there. However, how many people, so many opinions about how this program should work. Therefore, it is not surprising that, based on your driving experience and the characteristics of your car model, you will consider that the informant should work differently. In this case, write your own program. If you have never been involved in microprocessor programming, it's okay, you have to start everything for the first time. For the MCS-51 family of processors, there are many different compilers from many programming languages. There are BASIC-like compilers, and Pascal, and PLM, and Forth. If you have no idea about programming at all, it is convenient to start with Pascal. This language was developed at first as an educational language, but it turned out to be so successful that it was widely used by professionals. The Freeware version of Pascal for the MCS-51 can be found at named mpe_arc.exe. This is a completely working version with a 2 KB limit on the amount of generated code. But the codes generated by Pascal are far from optimal, so it is still better to master the C language, which is better adapted to single-chip microprocessors. Programs written in the C language, at first glance, look unusual and frighteningly incomprehensible. But this is just the beginning. Once you get comfortable with this language, you will find its syntax quite natural. You do not need the most complex concepts that professional programmers operate with. To write a working program, the basics are enough, they can be taken from the book "The C Programming Language" by B. Kernighan and D. Ritchie. This is one of the best C textbooks, written in a clear and easy to understand language. And let your first program be ugly from the point of view of a professional, let it be suboptimal in terms of volume, speed, but it will work, and it will be according to your algorithm. You will also need a compiler and a debugger. You can take any of the recommended in the previous issues of "Radio". The author used the Franclin Software debugger. As an example, consider the one shown in Table. 4 the test C program, designed to establish an informant. It is written without the use of C-specific pointers so that it can be easily translated into Pascal if needed. For simplicity, all variables are declared global. To reduce the amount of text, the program is not presented in full, but only for DS2. For DS3, you can easily add it yourself. Having added the extraction of sound from DS3 and seeing that everything is working out for you, you, guided by the program diagram in Fig. 1 of this article, you can start writing your program for processing signals from sensors. Literature
Author: A.Gordeev, Novosibirsk
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