I want to give signal via PLC to Raspberry Pi and when the raspberry pi gets that signal, it should run the python script and when the python script execute properly and cycle is completed, it should wait for the other signal from PLC to again run the same script and same cycle should go on.
Please provide some suggestions.
Via Network:
Depending on your PLC, you could use UDP or TCP, where a Python program on Raspberry listens and sends commands. Depending on the command received, different scripts ou actions could be executed. There are many Python examples for using this on the internet.
For the PLC it can be a little more complicated to find and it will depend on the model and manufacturer, I recommend that you check your supplier's documentation.
Discrete Inputs:
I don't recommend it, but if it's impossible to use a network, you could use discrete digital inputs (like buttons do) to trigger the scripts on the Raspberry, but it must have an interface with relays or optocouplers between the PLC and the Raspberry due to differences in types of electrical signals. In this mode, scripty in pyton keeps checking the status of a digital input and triggers the action when the status of the input changes.
Note:
Note that in both cases the program remains running (in an infinite loop), waiting for the command.
Additional care must be taken when using the Raspberry in an industrial environment due to possible interference by EMC. If using digital inputs, consider applying filters to the signal and shilded cables.
Related
Hallo this is my first post here.
I'm currently doing my internship at a company that uses twincat 3 programs for automation in conjunction with a yaskawa robot system. The assignment I received is to expand the simulation software they currently use to simulate the plc software to also be able to simulate the yaskawa interface so they can test if changes in eithers software causes issue's in the other without having to upload the program to a PLC. I've been looking online and found a couple options but I'm curious if I missed some other options or if the options I've found will not work.
The options I'm currently considering are.
using the ethernet port on the simulation pc to connect to the Yaskawa controller. I've found a driver(https://infosys.beckhoff.com/english.php?content=../content/1033/el7031-0030/1036996875.html&id=) that will allow the user to make an ethernet port on their pc function in real time so I theorized It might be possible to then directly connect the computer to the yaskawa controller so the user would not need to upload the software but have the PC act as a PLC instead.
Use ROS to simulate the robot. there are libraries for ROS industrial to program and simulate a yaskawa robot. It would require using 2 computers or using a virtual machine as ROS is used best on an linux system. Only problem is I can't figure out if the ROS simulation can use regular yaskawa jobs and functions or if it can only the adapted ones programmed in ROS.
Use motomans simulation software motosim to simulate the yaskawa robot. Seems like an obvious solution but can't figure out if it's possible to have it communicate with twincat3 however I might have missed something.
write a twincat 3 software that emulates a yaskawa interface. I consider this a last resort if all else fails. It would require the code be updated each time something about the yaskawa software changes which is not ideal for quick testing.
I'd really appreciate any suggestions or additional information more experienced programmers might have.
I'm building a HIL/SIL test with Simulink, which tests the Vehicle Control Unit(VCU) from a vehicle. This VCU talks with a Power Distribution Module(PDM) over a J1939 CAN network. The PDM handles the in- and outputs from switches and to actuators and puts the information on the CAN bus. The VCU then knows what the PDM is seeing from connected sensors. In turn, the VCU puts info on the CAN bus on how the PDM should control the connected actuators.
My laptop is hooked to the same CAN bus with a Vector adapter and Simulink.
To test the VCU, I need to mimic the PDM and send messages to the VCU as if I were the PDM. The VCU then has to take the correct actions and control the real PDM accordingly.
Obviously, if I just mimic the PDM, my messages will interfere with those sent from the real PDM. So basically, I need the PDM to shut up and only listen. I do the talking for the PDM. However, the PDM is not configurable in a listen-only mode, so I have to intercept all messages it sends so they never arrive at the VCU.
My idea was that i'd detect(by observing the arbitration field of all messages) when the PDM starts sending, and pull a bit down in the arbitration field. It'd recognise the priority of my 'message' over its own, and it'd stop transmitting. It'd be as if the CAN bus is always to busy to give room to the PDM. This would shut up the PDM without it throwing errors. But other suggestions are welcome.
So (how) is it possible to intercept J1939 CAN messages in MATLAB/Simulink, or with a separate CAN controller?
Here is an idea, how to realize what you are looking for. You need some extra hardware, however.
This is the rough outline:
Setup a CAN-gateway device, which has two independent CAN-interfaces can0 and can1.
Disconnect the PDM from the CAN-bus and connect it to one of the interfaces of your CAN-gateway, e.g. can0
Connect the second interface of the CAN-gateway, can1, to the original CAN-bus, which also includes your laptop and the VCU
Program your CAN-gateway to forward all incoming CAN-frames on can1 to the can0 interface
As you want to ignore all messages from the PDM, simply ignore the CAN-frames coming in on interface can0 and not forward them to can1
Example, how to realize such a CAN-gateway:
Hardware: Use a Raspberry Pi and a CAN extension board with two can-interfaces, such as the PiCAN2 duo board.
Software: Write a small program to forward traffic between the interfaces can0 and can1, using socketcan, which is already included in the Linux kernel.
In case your devices are communicating via the higher layer J1939 transport protocol, you might also need to get the J1939 transport protocol running on the Raspberry Pi. If you are simply using 29-bit indentifiers with a maximum payload of 8 byte of data, this should also not be necessary.
Alternatively, you could also use a more expensive commercial solution, this CAN-Router for example.
Your original idea:
I think what you are envisioning is technically feasible, but might have some other drawbacks.
As the drivers of can controllers typically don't expose interfaces to interactively manipulate CAN-frames while their transmission is still ongoing, you could directly address a can-transceiver from a microcontroller
A few researchers realized a CAN Denial of service attack by turning the first recessive bit in a CAN-frame after the arbitration ID into a dominant bit for certain selected CAN-IDs. They used an Arduino Uno and a Microchip MCP2551 E/P CAN transceiver. The code used is also available online. As this interactive manipulation of CAN-frames during transmission is related to what you are looking for, this could be a good starting point for you.
Still I see some drawbacks, when you silence the PDM this way:
You will not only silence the PDM this way, but also (at least) delay the transmission of other nodes on the CAN-bus with arbitration IDs that have
lower priority than the messages from the PDM
It is very likely that the PDM will go into some error state, when it is not able to successfully send its CAN-frames to the bus after a certain number of retries
Yet another idea:
In case you are able to adapt the software of the VCU, change it in a way that it does not consume the CAN-frames from the PDM, but CAN-frames from your laptop by using different CAN-IDs for the same messages. You will have to change the dbc-file for that purpose.
Hypothetical here: Let's say you have a processor attached to some form of USB-storage and a motor. How would I write a simple bare-metal program to tell the motor to move for 10 seconds? I want to learn how to bare metal program, and having a program to look at and analyze would be wonderful. (Any language would be great)
1) you have to understand how the processor in question boots. there is the core processor itself then the non-volatile storage. for example a raspberry pi is a little unique in that there is something in logic (or an on chip rom?) that reads the sd card, boots up the gpu, then the gpu copies the arm program to ram and releases the arm into that ram. most microcontrollers have on board flash and ram and the flash is mapped into the address space that the processor boots from and/or there is a vendor supplied bootloader that boots the processor then calls your code.
2) you have to learn how to enable and initialize the peripherals you care to use. a timer perhaps if you want to count to 10 seconds.
3) write the application.
debugging is the trick, you can sometimes use a hardware debugger via jtag or sometimes use a rom monitor via gdb or some other program on some interface like uart. or one that almost always is available either a blinking led or a uart to send text or numbers out to see what is going on. and of course an oscilloscope, you can wiggle gpios or do other things and see them on the scope.
driving a motor is too generic you need to specifically know what kind of motor and how to drive it, likely zero chance you are driving it directly from the microcontroller, you might have something outside a transistor h bridge or something that isolates the microcontroller or you have a specific type of motor driver chip/circuit that you speak to either through discrete signals, or i2c or spi, or other to tell it to drive the motor, and then maybe some analog to deal with the high power or maybe that chip is a hybrid. so you have to know all that or at least you have to know the programming side of all that, what interface and/or what signals have to have state changes in what way to cause the motor to do something. it could be as simple as a pwm that you create that is amplified between you and the motor. pwm may involve first learning how to mess with one of the timers then either another peripheral or a subset of the timer to make a pwm signal out of it. a scope is really helpful here too or a logic analyzer, or if you have another microcontroller you can sample a gpio in faster than the signal being generated you can turn it into a logic analyzer.
start with finding a board, blink an led, figure out how to run a timer, accurately blink an led. figure out the clock rates you are really running at instead of guessing, figure out how to configure the uart, send some characters out that, now you have a debug interface a knowledge of what your timer reference clock speeds are and can now try to count to 10 seconds, and then get into the signals needed for the motor. expect to blow up a few boards, buy some spares.
I am using STM32F205RGT6 Cortex-M3 microcontroller and coding with IAR Embedded Workbench.
I plan to keep the microcontroller in a power saving mode most of the time except when an external component tries to either communicate via SPI (the STM32 microcontroller is meant to be a SP slave) or via USB.
One external compinent is connected via SPI (PB12-15) and PC is connected via USB (PA11-12).
The communication works fine - I have tested both the SPI as well as USB.
I figured that once I am done setting up SPI and USB I will call a power saving function and add the same function call at the end of interrupt service routines. I have found PWR_EnterSTANDBYMode and PWR_EnterSTOPMode (in stm32f2xx_pwr.h) both of which I tried using.
However with such arrangement I cannot establish any communication (SPI or USB) with the microcontroller.
Is there something extra that needs to be configured (for example which pins should wake the microcontroller up)?
Am I using wrong function? Or wrong header file?
Can you point me to an example resembling such case (I could not find anything similar on ST's website)?
Any constructive feedback would be welcome.
In the mean time I found the application note AN3430 (http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/APPLICATION_NOTE/DM00033348.pdf) which is somehow more digestible (only 38 pages) which gives an excellent overview on power saving in the microcontroller.
Since I don't have access to PA0-WKUP (the wake-up pin) I had to discard using stand-by. Seems that just a simple sleep mode in main loop - by calling __WMI(); - should lower current consumption enough in my case. I might consider stop mode if sleep mode isn't enough but I will have read fragments of datasheet on configuration of EXTI registers that the application notepoints to.
There is a Simulink model composed of some subsystems, It is supposed to run each subsystem in a computer and all computers are connected to a LAN network.
There are interconnections between these subsystems and data shall be transferred between them so they should run synchronously and preferably real time.
But the computers have Windows operating system and so they do not have real time operating system.
I am searching to find a solution for this problem. what I have found up to now is that:
Simulink real time workshop can make executable code of simulink models but the code can be run real time just with real time processors and it doesn't seem that they can support connection between multiple computers.
XPC target is known but it just make connection between one host PC or hardware and one target PC and the target PC shall have real time OS. so it doesn't cover this problem.
There is a library for Matlab titled "Hardware Input / Output Library for Matlab / Simulink " by Werner.Zimmermann that have some good facilities such that it can make simulink to be run near real- time and it can make connection and send data via TCP/IP between two computers but it seems it can just make the connection between two computers running simulink.
It also have some constraints for OS and version of Matlab/Simulink and is not updated. So I'm not sure it would be enough.
After all of these, does anyone know a better way of handling this problem? I would appreciate any help on any of these topics to be useful or another ways to solve this problem.
Thanks in advance
see the following links (especially the first one):
http://www.mathworks.de/help/toolbox/instrument/brbv41k-1.html
http://www.mathworks.com/matlabcentral/fileexchange/4934
http://www.mathworks.com/matlabcentral/fileexchange/27290