Every year, automotive electrical circuits increased in size and complicated in the design. On the first vehicles released from Magneto, Ignition worked, and rechargeable battery And the generator was not at all. Acetylene burners were used in the headlights.
In 1975, the length of the wires in the automotive electrical circuit was equal to several hundred meters and was comparable to the electrical engineer aircraft.
The desire to simplify the wiring was such: only one wire is needed, connect all the consumers to it and to allow each control device. Skip the electrotocks to consumers to consumers and device control signals.
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By 1991, thanks to the breakthrough of digital technologies, Bosch and Intel created a CAN network interface for multiprocessor side computers systems. In electronics, such a system is called "tire".
In a serial bus (Serial Bus), the data is transmitted for a pulse over twisted pair (two wires), and in the parallel bus (Parallel Bus), the data goes along several wires at the same time.
With greater performance, parallel bus complicates the wiring of the car. The serial tire transmits information up to 1 Mbps.
Different blocks are divided by data, the rule by which this happens is called a protocol. The protocol can send to different blocks of the command, request data from one or all. In addition to the specific access to the device, the protocol may ask the importance and commands. For example, the engine cooling fan fan command will be a priority for lowering the side glass.
Minimizing modern electronics allowed to establish the release of cheap control modules and communication systems. In the automotive network they can be united in chains, stars and rings.
Information is in both directions, for example, turning on the lamp far LightThe signal will light up on the instrument panel - it shines or not.
The engine control system selects the best mode, receiving data from all chain devices, the lighting system will turn on or turn off the headlights, the navigation system will pave or change the route and so on.
Thanks to this protocol, the diagnostics of the engine and other devices of the car simplified.
The desire to have only one wire in the car was not implemented, but CAN - the module and data transfer protocol increased the reliability of the system and simplified the wiring.
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CAN Tire - What is it?
CAN - Tire ("Kan Tire") is a control system for all electrical devices and digital communication in a car that can receive information from devices between them to exchange data, as well as manage them. Data O. technical condition And the control signals go digital over twisted pairs due to the special protocol. From on-board network The car is meant to each consumer, but they are all connected in parallel. Such an option raised the reliability of the entire electrical circuit, reduced the number of wires and simplified the installation.
The appearance of digital tires in cars occurred later than they began to be widely implemented electronic blocks. At that time, the digital "output" was needed only for "communication" with diagnostic equipment - For this, there have been enough low-speed serial interfaces like ISO 9141-2 (K-Line). However, the apparent complication of on-board electronics with the transition to the CAN architecture has become its simplification.
Indeed, why have a separate speed sensor if the ABS block already has information about the rotation speed of each wheel? It is enough to transmit this information to the dashboard and in the engine control unit. For security systems, it is even more important: so, the airbag controller already becomes capable of drowning the motor in a collision independently, sending the corresponding command to the motor ECU, and de-energize the maximum onboard circuits, passing the command to the power management unit. Previously, it was necessary to safely apply not reliable measures like inertial switches and sopatrons on the battery terminal ( bMW owners With his "glitches" are already familiar well).
However, on the old principles, it was impossible to implement a full "communication" of the control blocks. The amount of data and their importance increased by an order, that is, it took a tire that is not only capable of working with high speed and is protected from interference, but also provides minimal delays in transmission. For moving at high speed, even milliseconds can already play a critical role. The decision satisfying such requests has already existed in industry - it's about CON BUS (Controller Area Network).
CAN-Tire essence
Digital CAN bus is not a specific physical protocol. The principle of operation of the CAN-tire, developed by Bosch in the eighties, allows it to realize it with any type of transmission - at least by wires, at least fiber, at least by radio channel. The Kan bus works with hardware support for block priorities and the possibility of "more important" to interrupt the transfer "less important".
To do this, the concept of dominant and recessive bits is introduced: Simplifying, the CAN protocol will allow any block at the right time to communicate, stopping the transfer of data from less important systems to the simple transmission of the dominant bit during the presence of a recessive bus. This happens purely physically - for example, if the "plus" on the wire means "unit" (dominant bit), and the absence of a signal is "zero" (recessive bit), then the transfer "Units" will definitely suppress "zero".
Imagine a class at the beginning of the lesson. Pupils (low priority controllers) calmly talk to each other. But, it is worth a teacher (a high priority controller) loudly give the "Silence in class" command, overlapping the noise in the class (the dominant bit suppressed recessive), as data transfer between the student controllers is stopped. Unlike the school class, in the Can-bus this rule works on an ongoing basis.
What is it for? In order for important data to be transferred to a minimum of delays even at the cost of the fact that unimportant data is not transferred to the bus (it features the CAN bus from a friend to Ethernet computers). In the event of an accident, the possibility of an injection computer to obtain information about this from the SRS controller is incommensurately more important than the dashboard get the next data speed data packet.
Modern cars have already become the norm of physical distinction of low and high priorities. They use two and even more physical tires of low and high speeds - usually this "motor" can-bus and "body", the flows of data between them do not intersect. Only the CAN bus controller is immediately connected to everything, which allows you to "communicate" with all blocks through one connector.
For example, Volkswagen technical documentation defines three types of used Can-tires:
- The "fast" tire, operating at the speed of 500 kilobit per second, combines the engine control units, ABS, SRS and transmission.
- "Slow" functions at a speed of 100 Kbps and combines the blocks of the Comfort system (central locking, windows and so on).
- The third works at the same speed, but transfers information only between navigation, built-in phone and so on. On old cars (for example, Golf IV), the information tire and the "Comfort" tire were physically combined.
Interesting fact: on the Renault Logan. The second generation and its "co-owners" are also physically two tires, but the second connects an exceptionally multimedia system with a CAN controller, and the engine computer is also present and the ABS controller, and the airbag, and the CEBBA.
Physically, cars with CAN-bus use it in the form of a twisted differential pair: it both wires are used to transmit a single signal, which is defined as the difference in voltages on both wires. It is necessary for simple and reliable noiselessness. The unshielded wire works like an antenna, that is, the source of radio interference is able to bring an electromotive force in it sufficient to the interference perceived by controllers as a really transmitted bit of information.
But in a twisted pair on both wires, the value of EMF interference will be the same, so the voltage difference remains unchanged. Therefore, to find a Can-bus in the car, look for a twisted pair of wires - the main thing is not to confuse it with the wiring of ABS sensors, which are also kept inside the vehicle with a twisted pair.
The CAN-tire diagnostic connector did not come up again: the wires were brought to free pins already standardized in the pads, in it can-tire on contacts 6 (CAN-H) and 14 (CAN-L).
Since CAN-tires can be somewhat on the car, it is often practiced to use on each different physical levels of signals. Again for example, refer to documentation Volkswagen.. This is how data transmission in the motor bus looks:
When data is not transmitted on the bus or recessive bit is transmitted, on both wires twisted, the voltmeter will show 2.5 V relative to the "mass" (the signal difference is zero). At the time of transferring the dominant bit on the CAN-HIGH wire, the voltage rises to 3.5 V, while the CAN-LOW is lowered to one and a half. The difference in 2 volts and means "one".
On the "Comfort" tire, everything looks different:
Here, "Zero" is, on the contrary, 5 volts of the difference, and the voltage on the LOW wire is higher than on the HIGH wire. "Unit" is a change in voltage difference to 2.2 V.
CAN-tire checking on the physical level is carried out using an oscilloscope, which allows you to see the real passage of signals along a twisted pair: the usual tester, naturally, "see" the alternation of impulses is impossible.
The "Decoding" of the car's CAN bus is also conducted by a specialized instrument - analyzer. It allows you to display data packets from the bus in the form you are transmitted.
You understand that diagnosis tires Can. On the "amateur" level without relevant equipment and knowledge does not make sense, and it is impossible trite. Maximum that can be made by "rented" means to check the channel - this is measuring voltages and resistance on the wires, comparing them with the reference for a particular car and a particular tire. This is important - we specifically led an example of the fact that even one car between the tires can be a serious difference.
Fault
Although the CAN interface and is well protected from interference, electrical malfunctions have become a serious problem for it. Combining blocks into a single network made it vulnerable. The cat-interface on cars has become a real nightmare of unqualified auto electrical plates Almost one of its features: strong voltage jumps (for example, winter) are capable of not only "hang" a CAN bus error detected, but also to fill the memory of controllers with sporadic errors, random character.
As a result, a whole "Garland" of indicators lights up on the dashboard. And, while the newcomer in the shock will scratch his head: "What is it?", Competent diagnostics first deliver a normal battery.
Purely electrical problems are the cliffs of the tire wires, their closures on the "mass" or "plus". The principle of differential transmission when the cutting of any of the wires or the "incorrect" signal is becoming unrealized on it. The worst of all the closure of the wire, since it "paralyzes" the entire tire.
Imagine a simple engine tire in the form of a wire, on which "sit in a row" several blocks - the engine controller, the ABS controller, dashboard and diagnostic connector. Open with the connector car is not afraid - all blocks will continue to transmit information to each other in normal mode, only diagnostics will be impossible. If you break the wire between the ABS controller and the panel, we will be able to see the scanner on the tire only it nor the speed, nor the engine speed will not show.
But when the cut between the ECU engine and ABS carMost likely, no longer becomes necessary: \u200b\u200bthe block, not "seeing" the controller you need (information about the speed is taken into account when calculating the injection time and the ignition ahead) will go into emergency mode.
If you do not cut the wires, but simply constantly submit to one of them "plus" or "mass", the car will "leave in knockout", since none of the blocks can transmit data to another. therefore golden Rule The auto electrician translated into the Russian censorship sounds like "do not climb the curves in the bus", and a number of automakers prohibits connecting to the CAN-tire of non-certified additional devices third-party production (for example, alarm).
Benefit Connecting a CAN-bus alarm is not a connector into a connector, but crashing directly into the car's bus, give a "crucial" to the installer the ability to confuse the wires in places. The car after that does not refuse to start - with the controller of the onboard chains that distribute power, even the ignition is not a fact that it turns on.
The onboard electronics of the modern car in its composition has a large number of executive and control devices. These include all sorts of sensors, controllers, etc.
To exchange information between them, a reliable communication network was required.
In the mid-80s of the last century, the Bosch company proposed a new CAN network interface concept (Controller Area Network).
The CAN bus provides connecting any devices that can simultaneously receive and transmit digital information (duplex system). Actually, the tire is a twisted pair. This sale of the tire made it possible to reduce the effect of external electromagnetic fields arising during the operation of the engine and other car systems. This tire provides a sufficiently high data transfer rate.
As a rule, the wires of the can-tire orange color, sometimes they differ in different colored stripes (CAN-HIGH - black, CAN-LOW - orange-brown).
Thanks to the use of this system from electrical circuit The car was released a certain number of conductors, which provided communication, for example, using the KWP 2000 protocol between the controller of the engine control system and the standard alarm, diagnostic equipment, etc.
The CAN-bus data transfer rate can reach up to 1 Mbps, while the speed of information transmission between the control blocks (motor - transmission, ABS is a security system) is 500 kbps (fast channel), and the speed of information transmission system "Comfort" "(safety pillow control unit, control blocks in car doors, etc.), the information and command system is 100 kbps (slow channel).
In fig. 1 shows the topology and shape of the CAN bus signals of the passenger car.
When transmitting information from any of the control blocks, the signals are enhanced by the receiving transmitter (transceiver) to the desired level.
Each block connected to the Can-bus has a certain input resistance, the result is a total load of the CAN bus. The overall load resistance depends on the number of electronic control units connected to the bus and executive mechanisms. So, for example, the resistance of the control units connected to the CAN bus power aggregateThe average is 68 ohms, and the "Comfort" systems and the information and command system - from 2.0 to 3.5 com.
It should be noted that when the power is turned off, it turns off the load resistance of modules connected to the CAN bus.
In fig. 2 shows a fragment of the CAN-tires with the load distribution in the CAN-HIGH, CAN-LOW lines.
Systems and car control units have not only different load resistance, but also data transfer rates, all this may interfere with the processing of differential signals.
To solve this technical problem A converter is used to communicate between the tires.
This converter is called a firewall, this device in the car is most often embedded in the design of the control unit, a combination of instruments, and can also be made in the form of a separate unit.
The interface is also used to enter and output diagnostic information, the request of which is implemented by the "K" wire connected to the interface or to a special CAN-bus diagnostic cable.
IN this case A big plus in conducting diagnostic work is the presence of a single unified diagnostic connector (OBD shoe).
In fig. 3 shows a block diagram of a firewall.
Should be taken into account that on some brands of cars, for example, on Volkswagen Golf. V, CAN-tires of the Comfort system and the information and command system are not connected by the firewall.
The table shows electronic blocks and elements related to the CAN-tires of the power unit, the "Comfort" system and the information and command system. The elements listed in the table and blocks in their composition may differ depending on the car brand.
CAN-tire malfunction diagnostics is performed using a specialized diagnostic equipment (CAN-tire analyzers) oscilloscope (including with built-in CHN bus analyzer) and digital multimeter.
As a rule, work to test the operation of the CAN bus starts with measuring the resistance between the tire wires. It should be borne in mind that the CAN-tires of the Comfort system and the information and command system, in contrast to the power unit, are constantly under voltage, so it should be disabled one of the battery terminals.
The main malfunctions of the CAN bus are mainly associated with the closure / breakdown of lines (or load resistors on them), a decrease in the level of signals on the bus, violations in the logic of its operation. In the latter case, the search for a defect can provide only the CAN-tire analyzer.
CAN-tires of a modern car
- CAN Tire of the Power Unit
- Electronic motor control unit
- Electronic control panel control unit
- Safety Pillow Management Block
- Electronic ABS control unit
- Electric power steering control unit
- Control unit TNVD
- Central Mounting Block
- Electronic ignition lock
- Steering wheel rotation angle sensor
- CAN-tire system "Comfort"
- Combination of devices
- Electronic door blocks
- Electronic parking control unit
Systems
- System control unit "Comfort"
- Block of the vocabulary of wiper
- Tire pressure monitoring
CAN-Tire Information Command System
- Combination of devices
- Sound Play System
- Information system
- Navigation system
Greetings all of you friends! The evolution of man gradually led to the fact that a modern car in the literal sense of the word, stuffed with all sorts of sensors and devices. There on the "board", as at the factory - a whole team. Of course, such a "brigade" must definitely manage! About this manager I want to talk to you today, namely, the cat-bus in the car is that it works according to which principle works and actually it appeared. About everything in order ...
A little story
Few people know that the most first cars did not have an absolutely no electrician. All that was needed to then drivers is a special magnetoelectric device to start a motor, which was capable of kinetic to work out electricity. It is not wonderful that such a primitive system delivered some inconvenience and, accordingly, was constantly upgraded.
So from year to year, wires and, accordingly different sensors It became more and more. It came to the point that the car has already begun to compare the car with an aircraft. It was then in 1970, it became obvious - for uninterrupted work, all chains need to be rationalized. After 13 years, the situation under its control took a cult brand from Germany called Bosch. As a result, in 1986, the Innovative Protocol CONTROLLER AREA NETWORK (CAN) was presented in Detroit.
However, even after the official presentation, the work remained to put it mildly, "so work on it continued.
- 1987 - Practical tests of CAN tires ended, which caused no less famous brands in the field of computer technology Philips and Intel.
- 1988 - Already the next year, another German Avtogan BMW introduced the first car operating on the CAN Tire technology, it was a favorite all model of the 8-series.
- 1993 - international recognition and, accordingly, the ISO certificate.
- 2001 - Cardinal changes in standards, now any European car must function according to the principle of "Kan".
- 2012 - the last update of the mechanism that has increased the list of compatible devices and the data transfer rate.
Here is such a long way our "director" of electrical appliances passed. You yourself see the experience not small, so such a high position is absolutely in the case).
CAN-Tire Definition
Despite its rich functionality, visually the cat-tire looks quite primitive. All its components are chip and two wires. Although at the very beginning of his "career" (80s), for contact with all sensors, it was necessary to more than a dozen plugs. It happened, because each individual wire was responsible for one single signal, now their number can reach hundreds. By the way, since we have already mentioned the sensors, consider what exactly is controlled by our mechanism:
- PPC;
- Engine;
- Anti-lock system;
- Safety bag;
- Wipers;
- Dashboard;
- Power steering;
- Kotrolls;
- Ignition;
- On-board computer;
- Multimedia system;
- GPS navigation.
Alarm with a can-bus, as you yourself understand also cooperates very closely. More than 80% of cars in the territory of the Russian Federation use the technology of Kan, and even the models of the domestic auto industry!
In addition, the modern cat-bus can not only check the equipment of the machine, but even eliminate some failures! And excellent isolation of all tool contacts, allows him to completely protect himself from any kind of interference!
Principle of operation of the CAN-Tire
So, the cat-bus is a certain verified transmitter, which is able to send information not only on two twisted wiring, but also by radio signal. The rate of information exchange can reach 1 Mbps, and several devices can use the bus simultaneously. In addition, CAN technology has nodes of personal clock generators, which allows you to send certain signals to all car systems at once!
The work schedule of our "leader", looks like this:
- Standby mode - Absolutely all systems are turned off, electricity only comes on the can-microchip, which is waiting for the team to "launch".
- Run - CAN activates all systems when turning the key in the ignition.
- Active exploitation - There is a mutual exchange of necessary information, including diagnostic.
- Sleep mode - immediately after disconnecting the power unit, the can-bus instantly terminates its activities, all systems "fall asleep".
Note: CAN technology is used not only in mechanical engineering, so in the "smart home" systems, it has been used for a long time ago and judging by the reviews, the chip copes with the tasks with the tasks with his bang!
Obviously, even today there is such an important unit to grow, in particular, this refers to the data transfer rate. Manufacturers are already doing some steps in this direction, for example, particularly intelligent reduce the length of the canvas wires, which makes it possible to increase the transfer rate of up to 2 Mbps!
Advantages and disadvantages
At the end of this publication, summing up so to speak, briefly consider all the pros and cons of this technology. Of course, let's start with the advantages:
- Simple and inexpensive installation;
- Speed;
- Resistance to interference;
- High level of safety from hacking;
- A huge assortment on any wallet, it is possible to choose the desired model to "Zaporozhets").
As for the minuses, they also have, but they are not so much:
- Not standardized top-level protocol;
- Virtually all traffic eats technical and official purposes;
- Every year of the selected amount of information that is transmitted simultaneously becomes less and less!
Actually, on this all, according to the old tradition, I attach a video in the topic! In it, you will learn how to check the cat-bus and can it be done at home. Before the new meetings of the Lord!
A task: Get access to the testimony of regular car sensors without installing additional.
Decision: Reading data from the car.
When it comes to monitoring such parameters as speed vehicle and Fuel consumptiona, reliable and spent solution is the installation of an autotraker and a fuel level sensor.
If access to such information as engine turnover, mileage, coolant temperature and other data with on-board computer - This task is already more like creative.
It would seem that it may be more logical: if in the car already have all the necessary sensors, then why install new? Almost everyone modern cars (especially if it comes to personal cars Business class and expensive special equipment) are regularly equipped with sensors, information from which enters the on-board computer.
The question consists only of how to access this information. For a long time, this task remained unresolved. But now in the satellite monitoring market, more and more highly qualified engineers who are still under the power to find a solution to the problem of correct receipt of such data as:
- engine speed;
- fuel level in the tank;
- car mileage;
- temperature of coolant engine TC;
- etc.
The decision we will talk about in this article consists in reading data from car bus.
. What ?
CAN (English Controller Area Network is a network of controllers) - a popular standard of an industrial network, focused on combining into a single network of various actuators and sensors, widely used in automotive automation. To date, almost all modern cars are equipped with a so-called digital wiring - automotive can-bus.
. Where did you come from the task of reading data from the CAN bus?
The task of reading data from the CAN bus appeared as a consequence of the task of optimizing the cost of operation of motor vehicles.
In accordance with the typical customer requests, cars and special equipment are equipped with a system of satellite GLONASS or GPS monitoring and a fuel turnover system (based on submersible or ultrasonic fuel level sensors).
But practice has shown that customers are increasingly interested in more economical ways of obtaining data, as well as such that would not require serious intervention in the design, as well as electric car.
It was this decision that the information from the CAN bus was obtained. After all, it has a number of advantages:
1. Savings on additional devices
No need to carry significant costs for the purchase and installation of various sensors and devices.
2. Saving a car warranty
The detection by the manufacturer of third-party intervention in the design or electric car is threatened with a practically guaranteed removal of a vehicle with warranty. And this is clearly not included in the sphere of the interests of the car owners.
3. Get access to information from standardly installed electronic devices and sensors.
Depending on the electronic system in the car, a certain set of functions can be implemented. To all these features, theoretically, we can access CAN bus. It can be mileage, fuel level in gas tank, opening / closing of doors, temperature overboard and in the cabin, engine speed, speed, etc.
Technical specialists from Skyshim chose to test this solution to the device. It has a built-in FMS decoder and can read the information directly from the CAN bus.
. What advantages and disadvantages entails a solution to read data from the CAN bus?
Advantages:
Ability to work in hard real-time mode.
. Easy to implement and minimal use costs.
. High resistance to interference.
. Reliable control of transmission errors and reception.
. Wide range of speeds.
. Large technology distribution, the presence of a wide range of products from various suppliers.
Disadvantages:
The maximum network length is inversely proportional to the transfer rate.
. Large size of service data in the package (with respect to useful data).
. The absence of a single generally accepted standard for a high-level protocol.
The network standard provides ample opportunities for practically unmistakable data transmission between nodes, leaving the developer the opportunity to invest in this standard everything that can fit there. In this regard, the CAN bus is similar to a simple electrical wire. There you can "Show" any stream of information that can withstand the tire bandwidth.
Known examples of sound transmission and images via CAN bus. The case of creating an emergency communication system along a high-tens of tens of kilometers long (Germany) is known. (In the first case, there was a high transmission rate and a small length of the line, in the second case, on the contrary).
Manufacturers, as a rule, do not advertise, how exactly they use useful bytes in the package. Therefore, the FMS device can not always decrypt the data that "gives" a CAN bus. In addition, not all car brands have a Can-bus. And not even all cars of one brand and models can give the same information.
Example implementation example:
Not so long ago, Skyshim, together with a partner, a large project for monitoring vehicles was implemented. In the park were different trucks Foreign production. In particular, SCANIA P340 trucks.
In order to analyze the process of obtaining data from the Can-tire, we, by mastering the customer, conducted appropriate studies on three SCANIA P340 cars: one 2008 release, the second beginning of 2009 and the third end of 2009.
The results were as follows:
- from the first data were obtained and were not;
- only a mileage was obtained from the second;
- from the third, all of interest in the data (fuel level, coolant temperature, engine turnover, total consumption, general mileage) were obtained.
The figure shows a fragment of the message from the WiLon information system, where:
Fuel_level - fuel level in the tank in%;
TEMP_AQUA - coolant temperature in degrees Celsius;
Taho - data from tachometer (rpm).
The rules for the implementation of the decision was the following:
1. Galileo GLONASS / GPS navigation instrument was connected to the truck CAN bus.
This autotraker model was chosen due to the optimal combination of functionality, reliability and cost. In addition, it supports FMS (Fuel Monitoring System) - a system that allows you to register and monitor the main parameters of the use of the vehicle, i.e. Suitable for connecting to the CAN bus.
The CAN-bus connection scheme from the Galileo device can be found in the user manual. To connect from the car, it is necessary, first of all, to find a steam pair of wires suitable for the diagnostic connector. The diagnostic connector is always in accessibility and is located near the steering column. In the 16 contact connector according to the OBD II standard it is 6-CAN High, 14-Can Low. Please note that the high voltage wires are approximately 2.6-2.7V, in Low wires, it is usually 0.2 liters less.
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Another unique solution that was used to withdraw data from the CAN bus was the contactless CAN CROCODILE data reader (production of joint venture Technoton, Minsk). It is perfect for working with Galileo devices.
Advantages of CAN Crocodile technology:
CAN Crocodile allows you to receive data about the car from the CAN tire no interference in the integrity of the tire itself.
Data reading occurs without mechanical and electrical contact with wires.
CAN CROCODILE is used to connect to the CAN bus / GLONASS monitoring bus that receive information about the engine operation modes, the state of the sensors, the presence of faults, etc.
CAN Crocodile does not violates CAN wires and "listens" over the bus using a special wireless receiver.
The use of CAN Crocodile is absolutely safe for the car, imperceptibly for the operation of the on-board computer, diagnostic scanner and other electronic systems. Especially relevant use of CAN Crocodile for warranty vehicles in which the connection of any electronic devices to the CAN bus often serves as a reason for removing warranty.
2. If the wires are detected and identified correctly, you can start the can-scanner in the Galileo instrument.
3. The FMS standard is selected, speed for most cars 250,000.
4. Start scanning.
5. After the scan is completed, switching to the main page of the configurator. If the scan is completed successfully, we get access to decrypted data.
6. If nothing but "End Scan" you have not seen, there are several options. Either a connection was incorrectly carried out, or the car for some reason does not produce data, or the device is unknown by the cipher of this CAN bus. As already mentioned, this happens quite often, since there is no single standard for transmission of data and their CAN processing. Unfortunately, as practice shows, it is not always possible to get full data from the CAN bus.
But there is another moment that is important to affect.
Most often, the main purpose of customers is to control the level and consumption of fuel.
Even if data from regular sensors will be successfully obtained from the CAN bus, what is their practical value?
The fact is that the main purpose of the full-time fuel level sensors is to evaluate with the degree of accuracy that seems to be the right manufacturer of TC. This accuracy can not be shown with an accuracy that the submersible fuel level sensor (dip) produces Omnikim Or, for example, TechNoton.
One of the main tasks that the staff is solved is that the fuel suddenly did not end, and the driver understood the overall situation with the fuel level in the tank. From simple to its device, a regular float sensor is difficult to expect great accuracy. In addition, there are cases when a regular sensor distorts data (for example, when transport is located on the slope).
conclusions
For a number of above-mentioned reasons, we recommend not to rely on the readings of the standard fuel level sensors, and consider each situation individually. As a rule, the appropriate solution can be found only together with technical experts. W. different manufacturers TC Different readings accuracy. All customers also have different tasks. And only under a specific task it is advisable to select a solution tools. Someone is quite suitable for obtaining data from the CAN-tire, as it is at times cheaper and does not require any changes. fuel system TC. But to customers with high demands on accuracy reasonably consider the option with the immersion Dutch.
