Description
2351 Invensys Triconex system
2351 Invensys Triconex system
Module Clips Drive controller servo motor
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Definition of IO Link Protocol and Its Interface
IO Link is a peer-to-peer, serial digital communication protocol designed for periodic data exchange between sensors/actuators and controllers (PLCs). The IO Link protocol was first proposed by Siemens and has now become an international standard IEC 61131-9. With the advancement of Industry 4.0, the use of IO Link is becoming increasingly widespread. Today”s article will introduce the definition of the IO Link protocol and its interfaces.
Factory automation can be divided into execution layer, on-site layer, on-site control layer, workshop control layer, and management layer according to functional division. As shown in the following figure:
The execution layer includes various execution mechanisms (valves, pumps, motors, etc.) and sensors, which are the muscles and peripheral nerves of factory automation. They receive commands from the upper layer and complete specified actions.
The on-2351 Invensys Triconex system site layer includes various distributed IO2351 Invensys Triconex system systems, which are the central nervous system of factory automation. It conveys control instructions from the upper layer to the execution layer; And feedback the signals from the execution layer to the control layer, serving as the information center;
The on-site control layer includes various PLC systems, which are the brains of factory automation. It issues corresponding instructions and commands the execution layer to complete corresponding actions based on internal program requirements and signal feedback from the execution layer;
The workshop control layer (MES) and management layer communicate with various PLC systems at the management level to complete management tasks at the workshop and factory levels.
The IO Link protocol to be introduced in this article is a protocol that transfers data between the execution layer and the field layer. An IO Link system consists of the following components:
1) IO Link Master;
2) IO Link Device;
3) Non shielded 3-5 core standard cable;
4) Tools for configuring IO Link parameters;
The IO Link Master transfers data between the IO Link device and the PLC. It is usually a distributed IO module with IO Link connection channels on the module. The IO Link Device is connected to the channel of the IO Link Master through a cable, and the IO Link Master exchanges data with the PLC through a bus. As shown in the following figure:
Every IO Link device needs to be connected to a channel of the IO Link supervisor, so IO Link is a peer-to-peer communication protocol, not a bus protocol.
IO Link devices are divided into two types: sensors and actuators: sensors are usually the four pin interface of M12, and actuators are usually the five pin interface of M12.
According to IEC 60974-5-2, the definition of IO Link Device pins follows the following regulations:
1) Pin 1 (PIN1): 24V power supply positive pole;
2) Pin 3 (PIN3): 0V
3) Pin 4 (PIN4): IO Link communication or standard IO output;
The pin definition of the IO Link device is shown in the following figure:
Which types of equipment should PLC module manufacturers develop first?
We know that PLC, also known as programmable logic controller, collects variable data through various IOs to achieve the purpose of automated control. Therefore, developing PLC is largely about developing IO. However, with so many types of IO, which PLC module manufacturers should develop first? Let me share my opinion:
1. Digital input IO, including PNP and NPN digital input IO, counter input IO, etc.
2. Digital output IO, including PNP and NPN digital output IO, PWM pulse output IO, relay output IO, and so on.
3. Analog input IO, including current acquisition input IO, voltage acquisition input IO, temperature acquisition input IO, and so on. The current input IO can collect currents ranging from 0 to 20 milliamperes, while the voltage input IO can collect voltages ranging from negative 10V to positive 10V. Temperature acquisition IO includes thermocouples and thermal resistors.
4. The style of analog output IO is similar to that of analog input IO, but does not include temperature analog, mainly voltage and current type.
Modify the watchdog time of the PROFINET IO device under 16 STEP7
3.2 Check if the installation of PROFINET IO communication equipment meets the specifications
Most cases of PROFINET IO communication interference problems are caused by equipment installation that does not comply with the installation specifications for PROFINET IO communication, such as incomplete shielding, unreliable grounding, and being too close to interference sources. Installation that meets the specifications can avoid communication failures caused by electromagnetic interference. You can refer to the following brief installation requirements for PROFINET:
1. Wiring of PROFINET 2351 Invensys Triconex system
In order to reduce the coupling of electric and magnetic fields, the larger the parallel distance between PROFINET and other power cable interference sources, the better. In accordance with IEC 61918, the minimum distance between PROFINET shielded cables and other cables can be referred to Table 1. PROFINET 2351 Invensys Triconex system can be wired together with other data cables, network cables, and shielded analog cables. If it is an unshielded power cable, the minimum distance is 200mm.
Comprehensive analysis of the principle and application skills of microcontroller IO port
IO port operation is the most basic and important knowledge in microcontroller practice. This article takes a long time to introduce the principles of IO ports. I also consulted a lot of materials to ensure the accuracy of the content, and spent a long time writing it. The principle of IO ports originally required a lot of in-depth knowledge, but here it has been simplified as much as possible for easy understanding. This will be of great help in solving various IO port related problems in the future.
The IO port equivalent model is my original method, which can effectively reduce the difficulty of understanding the internal structure of the IO port. And after consulting and confirming, this model is basically consistent with the actual working principle.
I mentioned a lot earlier, and many people may already be eager to actually operate microcontrollers. The IO port, as the main means of communication between the microcontroller and the outside world, is the most basic and important knowledge for microcontroller learning. Previously, we programmed and implemented an experiment to light up the LED at the IO port. This article will continue to introduce the relevant knowledge of the IO port.
In order to better learn the operation of IO ports, it is necessary to understand the internal structure and related concepts of IO ports. These knowledge are very helpful for subsequent learning, with a focus on understanding and no need to memorize them intentionally. If you don”t remember, just come back and take a look. If you use it too much, you will naturally remember.
We have said that the most accurate and effective way to understand a chip is to refer to official chip manuals and other materials. But for beginners of microcontrollers, it may be difficult to understand the chip manual directly, especially when they see a bunch of English, unfamiliar circuits, and terminology. If it were me, I would definitely be crazy. But here I still provide a picture taken from Atmel”s official “Atmel 8051 Microcontrollers Hardware Manual”.
The purpose of giving this picture is not to dampen everyone”s enthusiasm for learning, but to help everyone understand how the various microcontroller materials we have seen come from and whether they are accurate. All of these can be clarified through official information, which will be helpful for everyone to further learn something in the future.
Introduction to the Second Function
The above figure is the authoritative 51 microcontroller IO port structure diagram provided by the official. It can be seen that the internal structure of the four sets of IO ports of the microcontroller is different, because some IO ports have a secondary function, as mentioned in the introductory section.
Do you remember this pin diagram? The second function name of the IO port is marked in parentheses. Except for P1, each interface has a second function. When introducing the microcontroller system module, I mentioned that the 51 microcontroller has an interface for reserved extended memory, which is the second function of P0 and P1 in the figure (while also using pins such as 29 and 30). Because it is not widely used and involves in-depth knowledge, no specific research will be conducted. By the way, the AD0~AD7 we see here are actually used for parallel ports. The second function of the P3 port, including serial port, will be introduced in detail later.
The drawbacks of network IO and the advantages of multiplexing IO
In order to talk about multiplexing, of course, we still need to follow the trend and adopt a whiplash approach. First, we will talk about the drawbacks of traditional network IO and use the pull and step method to grasp the advantages of multiplexing IO.
For the convenience of understanding, all the following code is pseudo code, and it is sufficient to know the meaning it expresses.
Blocking IO
The server wrote the following code to handle the data of client connections and requests.
Listenfd=socket()// Open a network communication port
Bind (listenfd)// binding
Listen (listenfd)// Listening while (1){
Connfd=accept (listenfd)// Blocking connection establishment
Int n=read (connfd, buf)// Blocking read data
DoSomeThing (buf)// What to do with the data you read
Close (connfd)// Close the connection and wait for the next connection in a loop
}
This code will be executed with stumbling blocks, just like this.
It can be seen that the thread on the server is blocked in two places, one is the accept function and the other is the read function.
If we expand on the details of the read function again, we will find that it is blocked in two stages.
This is traditional blocking IO.
The overall process is shown in the following figure.
So, if the client of this connection continues to not send data, the server thread will continue to block on the read function and not return, nor will it be able to accept other client connections.
This is definitely not feasible.
Non blocking IO
To solve the above problem, the key is to modify the read function.
A clever approach is to create a new process or thread every time, call the read function, and perform business processing.
While (1){
Connfd=accept (listenfd)// Blocking connection establishment
Pthread_ Create (doWork)// Create a new thread
}
Void doWork(){
Int n=read (connfd, buf)// Blocking read data
DoSomeThing (buf)// What to do with the data you read
Close (connfd)// Close the connection and wait for the next connection in a loop
}
In this way, once a connection is established for a client, it can immediately wait for a new client connection without blocking the read request from the original client.
However, this is not called non blocking IO, it just uses multithreading to prevent the main thread from getting stuck in the read function and not going down. The read function provided by the operating system is still blocked.
So true non blocking IO cannot be achieved through our user layer tricks, but rather by imploring the operating system to provide us with a non blocking read function.
The effect of this read function is to immediately return an error value (-1) when no data arrives (reaches the network card and is copied to the kernel buffer), rather than waiting for blocking.
The operating system provides this feature by simply setting the file descriptor to non blocking before calling read.
Fcntl (connfd, F_SETFL, O_NONBLOCK);
Int n=read (connfd, buffer)= SUCCESS;
In this way, the user thread needs to loop through the call to read until the return value is not -1, and then start processing the business.
We noticed a detail here.
Non blocking read refers to the stage where data is non blocking before it reaches the network card, or before it reaches the network card but has not been copied to the kernel buffer.
When the data has reached the kernel buffer, calling the read function is still blocked and requires waiting for the data to be copied from the kernel buffer to the user buffer before returning.
The overall process is shown in the following figure
IO multiplexing
Creating a thread for each client can easily deplete the thread resources on the server side.
Of course, there is also a clever solution. After accepting each client connection, we can put the file descriptor (connfd) into an array.
Fdlist. add (connfd);
Then create a new thread to continuously traverse the array and call the non blocking read method for each element.
While (1){
For (fd “- fdlist){
If (read (fd)!=- 1){
DoSomeThing();
}
}
}
In this way, we successfully processed multiple client connections with one thread.
Do you think this means some multiplexing?
But this is just like using multithreading to transform blocked IO into seemingly non blocking IO. This traversal method is just a small trick that our users have come up with, and every time we encounter a read that returns -1, it is still a system call that wastes resources.
Making system calls in a while loop is not cost-effective, just like making rpc requests while working on distributed projects.
So, we still need to plead with the operating system boss to provide us with a function that has such an effect. We will pass a batch of file descriptors to the kernel through a system call, and the kernel layer will traverse them to truly solve this problem.
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