I am an electronics enthusiast and a "universal repairman" with more than 20 years of repair experience. Below are some of my repair stories.
Not long ago, I received a consultation from a dealer (hereinafter referred to as Mr. W), asking me whether the B brand can be repaired in addition to the H brand that I often repair. Although I don't know much about Brand B, I know that although the brands are different, their framework is the same, and the specific product details are different. Of course, I couldn’t refuse the person who came to send money. I immediately said “Of course.” Although I said it confidently, I was inevitably a little worried. Because my one-time maintenance success rate is above 80%, if I rashly take over an unfamiliar product, if the car overturns, it will damage my reputation and self-esteem.
From 2015 to 2018, I worked in an electronics factory that produced fire protection products. The factory owner is doing intelligent evacuation system and EPS. My main job is to do after-sales technical support work, which is responsible for thoroughly researching the problems encountered by the department and guiding after-sales engineers. I am well aware that the company's products do not strive for perfection, so I tried to make adjustments through after-sales port patching.
The boss wanted to play big, but he was not greedy enough, the capital chain was broken, and the factory was killed. Although I am an ant, I have the ambition of an elephant. But I am just an ant after all, without the strength of an elephant. Not only could it not prevent the elephant from falling, but it also did not choose to avoid danger when the elephant fell, and was crushed by the fallen elephant. . . I paid too much, and the harvest was miserable, and I was deeply hurt by hundreds of thousands of yuan in negative assets in an instant.
In the next few years, I have been working as a freelancer, occasionally doing small after-sales service jobs to make ends meet, researching technology when I have nothing to do, and learning about single-chip microcomputers. But after all, the debt problem cannot be solved. After paying the social security, the debt has been expanding.
Compared with the ordinary evacuation system, the intelligent evacuation system has a great feature, that is, all the lamps are connected to the upper computer through the distribution box. All control is decided by the upper computer. With the host computer, it is worthy of the word "smart". For our company's products, the upper computer sends commands to the distribution box through the CAN bus, and the distribution box sends them to the lamps through the MBUS or POWERBUS bus.
The upper computer of the company's products is made up of PC motherboards. The operating system is Windows.
The software composition of the upper computer was designed by the technical vice president who knew nothing about software.
The software code of the upper computer was typed by a coder from a certain training class. There are many bugs. There is no intention to discriminate against the training class here. After all, the teachers of the training class do not teach coders to code bugs. The number of bugs depends on the character of the coder and the character of the boss.
From the upper computer to the distribution box, it is the CAN bus. CAN is an advanced field bus, CAN has more advantages than 485, there is nothing wrong with it. However, the CAN bus is not as easy to tune as the 485. If the tuning is not good, it will overturn, such as my company.
What should I do if the upper computer does not have a CAN interface? The network port comes together. In the early stage, I spent a few hundred yuan to buy a finished network port-to-CAN gateway, and later developed and designed a network port-to-CAN gateway by myself, reducing the cost to tens of dollars, so that the upper computer is assembled.
If cost control and the convenience of programming with the host computer are considered, wouldn't it be more appropriate to use 232 to CAN? But no one understands, no one optimizes, and no one designs like this.
On the project site, often a host computer carries the distribution boxes of many buildings, and the height of the buildings is very high, so the communication lines will be far away; the construction team does not know the CAN bus, and does not know the need to avoid strong electricity Lines, I don’t know that they need to be connected hand in hand, and I don’t know that shielded twisted pair wires are needed. But they deeply know that saving money and labor is the most important thing. The wiring of the strong electric bridge, the twisted-pair wires were replaced by parallel wires, and the hand-in-hand finally became a tree connection. The terminal resistors did not know where to add, so the final communication success rate was terrible. This requires the CAN bus speed to be as low as possible in order to solve the problem flexibly.
The distribution box control board in our factory uses 51 single-chip microcomputer + SJA1000 + 82C250, the design of this mature solution is wrong, the mode pin is suspended, the chip sometimes works in intel mode, sometimes works in Motorola mode; 82C250 can work at the lowest Working at 5K, our rate is fixed at 50K and does not support manual adjustment; the program does not do fault-tolerant processing for interference, causing CAN nodes to shut down communication due to accumulated errors; CAN self-recovery insurance quality is not good, and CAN cannot communicate after long-term operation; communication The protocol is completely copied from 485, and the data is directly transmitted through CAN, and the CRC16 check is added, which loses the advanced nature of CAN... Hey, use it so-so. Why is the boss not willing to spend money to recruit people, only to find some 250. No, the biggest 250 is the boss, because if there is a problem below, you have to look up.
I have always had an idea to cancel the network-to-CAN converter and use the serial port to CAN on the host computer to realize networking. In this way, the cost is low, the circuit is simple, and the programming of the upper computer is easier. So I often search for related products in a certain treasure. Finally, one day I got a USB-to-CAN device from a railway aviation company.
The main purpose of a certain railway company developing this device is that they have extended the CANID protocol and need a kind of hardware to facilitate verification and use of their protocol. Their hardware is elegantly designed and very easy to use. When the USB is inserted into the computer, a virtual serial port will be generated, and the host computer controls the CAN through the baud rate, parity bit and stop bit transmitted when the virtual serial port is opened. Among them, the baud rate controls the CAN baud rate, using 9600 to represent 10K, and 19200 to represent 50K, and a total of 8 commonly used baud rates are preset; the parity bit controls the log mode or the working mode, uses none to represent the log mode, and odd to represent Working mode; the stop bit controls the sending and receiving mode, 1 means it can be sent and received, and 1.5 means it can only eavesdrop. With the above functions, it is actually equivalent to a CAN analyzer. However, the main CAN analyzer is cheap, only 30 yuan. The disadvantage is that CAN does not have isolation, and there is a certain probability that it cannot communicate with CAN. It needs to be connected to CAN first, and then connected to the computer.
This little baby can not only participate in the analysis of CAN protocol, but also send CAN data. Its format is 0xAA CC 12345678 08 11 22 33 44 55 66 77 88 DD. Among them, 0xAA represents the header, 0xCC represents the extended frame of 29-bit CANID, 0x12345678 represents CANID, 0x08 represents the data length, 0x1122334455667788 represents the data, and 0xDD represents the end of the packet. This device cooperated with the 51+SJA1000 programming that I learned for a period of time, and then it was stored away to eat ashes. This learning process has brought convenience to my future maintenance.
Mr. W is a distributor of other brands of smart evacuation, and we have only had an intersection since last year. The reason for the intersection is because there is a project with dual-brand supply, he is responsible for the supply of the B brand, and we are responsible for the supply of the H brand. The upper computer of the H brand was broken, and no repairer could be found, and the delivery could not be delivered, so the general contractor asked Mr. W to help find someone to repair. Mr. W found the N brand business, and the N brand business found the technology of our H brand agent, and finally found me. The line is a bit long, it's like connecting hand in hand. . . . .
Since helping Mr. W solve the problem, Mr. W has firmly remembered me. When he had a problem with his own project, he thought of asking me to help solve it.
As mentioned earlier, Mr. W contacted me to ask if the B brand can be repaired. At that time, I fully agreed. After more than 10 days, Mr. W sent a message again, saying that it can be repaired. He didn't know the details of the fault. He just said that the sign lights in some areas of the underground garage were not on, and they needed to be lit, and they could be repaired while checking. After all, they are business people, and they are only responsible for eating, drinking, drinking and having fun with customers. They know nothing about technology, which is understandable.
For brand B, I only know that a former colleague of mine who has a good relationship has joined the after-sales team of the brand (he has since left), so you can consult him if you have any questions. I don't know anything about other technical details, and I'm still nervous. So I prepared a trunk of supplies, and even brought an oscilloscope and a heat gun.
The project is not far from home, a two-hour drive. When we arrived at the destination, we got in touch with the property manager. The property manager greeted me warmly, almost giving me a hug. He said: You know, several groups of people came, but nothing was resolved. We searched floor by floor, five or six floors, and finally found you.
The manager led me to the scene, pointed to the unlit evacuation lights, and told me that this was the case, and the people in front couldn't solve it, saying that something should be upgraded.
I see that these lights are indeed not on, but the communication indicator is flashing regularly, and the power supply should be fine. I checked it with a multimeter, and it's true. There is a test button on the distribution box, press the button, the lights are on; release the button, the lights are off.
Our industry often encounters reputable dealers, who often fail to pay according to the contract rhythm. You can't blame them all, they still have Party A, and Party A's failure to pay will cause the dealers to fail to perform the contract in time. In order to maintain sales volume and business relationship, manufacturers generally do not sue dealers, but pretend to be grandchildren and slander dunning money. In order to solve the problem of installing a grandson, the manufacturer added an authorization function to the upper computer software. After a certain period of time, the system will be paralyzed, and the system will be reactivated after the dealer pays the payment, so that the grandson will become a grandfather.
I think maybe I have an authorization problem. Go to the host computer to check, sure enough, the software interface shows "unauthorized". Reset and emergency functions cannot be used, only inspection is available. No wonder the first few groups couldn't figure it out.
Call the dealer Mr. W to ask if there is any economic dispute. W said that he bought the goods from the upper-level agent, and the payment has been fully paid to the upper-level distributor. As for whether the previous family has the full payment, he is not sure. He said that after a problem with the project, he applied for the service through his home, but he couldn't be urged many times, and he quarreled with his home, but it was useless. There was really no other way, so I was invited to appear at my own expense.
I contacted the after-sales service of Brand B through my personal relationship, that is, the former colleague of my former colleague, referred to as Mr. G. Mr. G said that he knew about the project, and there was indeed a case where the delivery order was rejected in the past. The reason was that the service could not be provided because of the arrears. Moreover, the business of the factory has been explained, and the after-sales personnel of the manufacturer are strictly prohibited from intervening in this matter.
Do I have to make a trip for nothing? I will continue to communicate with Mr. G, can I temporarily authorize him to turn on the light first. Mr. G said that they do not have permission, only business personnel have permission to apply. Mr. G also said that the dispute was caused by the arrears of other projects, and the manufacturer forced the big dealer above Mr. W to pay for other projects by stopping the service.
Business people are so arrogant! Do you want to force me to make a bigger move?
The upper computer of brand B is a Linux system, and the database is SQLite. I'm new to both ancestors, don't know the root password nor the SQLite password, the software is also dongle protected, and the maintenance is stuck. . .
To know what happened next, please see the next article:
(The code word is not easy, please indicate the source for reprinting)