I try to convert modbus tcp data formats in different types like Bool/Float/String/U16/U32 and S16/S32.
If I understand S16 and S32 are custom data formats of the manufacturer.
For the float I follow this guide Reading 32 bit Float from modbus TCP using node red and it's work fine.
Someone can explain me how to do the same for the others types of data ?
Here is my flow
The full PDF of the modbus server is here:
http://cloudzola.quickconnect.to/d/f/560350335902727299
Exactly the same way as described in the answer you linked to.
Just instead of calling readFloatBE() you want to call readInt16BE() on the buffer.
Have a look at the documentation for the NodeJS Buffer object for the different available methods to read/write different sized fields.
Related
For a work project, I have to read a bunch of holding registers from an IFM CR1203 PLC that is programmed using CODESYS 3.5.
The PLC will be running a slave instance and the device reading the holding registers will be a PC running a custom application programmed in Javascript to be a client. I have already programmed MODBUS TCP/IP functions for the custom application that is tested and works (For a previous project I had to do the same for a different PLC programmed using a different platform).
My current issue is that I need the raw memory address of the first holding register to do this, but I can't find it on the CODESYS IDE. CODESYS uses an addressing system that makes it easy for different CODESYS-based devices to communicate. Here is a link that explains how it works: CODESYS MODBUS register location guide
The only thing that looks like it can work is from the link above:
<memory position> : <number> ( .<number> )* // Depends on the target system
But I don't fully understand what all that means.
I also can't find any documentation on the PLC or CODESYS that explains this topic in enough detail. Here is a snippet of dummy code used for testing that shows the CODESYS addresses:
Can someone please explain to me how I can convert the value %IW0 to a raw memory address, for example, 0xFFFF?
I use Machine Expert (Codesys 3.5.16) and in their documentation says:
The I/Os are mapped to Modbus registers from the master perspective as follows:
%IWs are mapped from register 0 to n-1 and are R/W (n = Holding register quantity, each %IW register is 2 bytes).
%QWs are mapped from register n to n+m -1 and are read only (m = Input registers quantity, each %QW register is 2 bytes).
So in your example they should be address 0 and 1.
Summary:
I am writing a server in Ada that should listen and reply to messages received over UDP. I am using the GNAT.Sockets library and have created a socket and bound it to a port. However, I am not sure how to listen for and receive messages on the socket. The Listen_Socket function is for TCP sockets and it seems that using Stream with UDP sockets is not recommended. I have seen the receive_socket and receive_vector procedures as alternatives, but I am not sure how to use them or how to convert the output to a usable format.
More details:
I am writing a server that should reply to messages that it gets over UDP. A minimal example of what I have so far would look like this:
with GNAT.Sockets;use GNAT.Sockets;
procedure udp is
sock: Socket_Type;
family: Family_Type:=Family_Inet;
port: Port_Type:=12345;
addr: Sock_Addr_Type(family);
begin
Create_Socket(sock,family,Socket_Datagram);
addr.Addr:=Any_Inet_Addr;
addr.Port:=port;
Bind_Socket(sock,addr);
-- Listen_Socket(sock); -- A TCP thing, not for UDP.
-- now what?
end UDP;
For a TCP socket, I can listen, accept, then use the Stream function to get a nice way to read the data (as in 'Read and 'Input). While the Stream function still exists, I have found an archive of a ten year old comp.lang.ada thread in which multiple people say not to use streams with UDP.
Looking in g-socket.ads, I do see alternatives: the receive_socket and receive_vector procedures. However, the output of the former is a Stream_Element_Array (with an offset indicating the length), and the latter has something similar, just with some kind of length associated with each Stream_Element.
According to https://stackoverflow.com/a/40045312/7105391, the way to change these types into a stream, is to not get them in the first place, and instead get a stream, which is not particularly helpful here.
Over at this github gist I found , Unchecked_Conversion is being used to turn the arrays into strings and vice versa, but given that the reference manual (13.13.1) says that type Stream_Element is mod <implementation-defined>;, I'm not entirely comfortable using that approach.
All in all, I'm pretty confused about how I'm supposed to do this. I'm even more confused about the lack of examples online, as this should be a pretty basic thing to do.
I am in the process of programming some sort of USB oscilloscope.
I followed the tutorial, using a STM32F429.
https://www.youtube.com/watch?v=MmwR1VU_rVc&list=PLnMKNibPkDnHxpOv2HETihQy5HHQGv2nS&index=26
The tutorial was very helpful with this and I am able to use the software from the tutorial (stmscope) to see the incoming data.
However, I would like to process the data in Matlab, where my problems start. As far as I understand the baudrate does not matter, because there is no real UART connection?
For reading the UART in another project I used for example "Putty" or "SerialMonitor". By specifying the baudrate and the com port the readout was quite easy, even in Matlab.
The used USB port is simulated as a virtual com port and the data is sent with CDC_transmit. However, with the previous methods "Putty" or "SerialMonitor" I cannot read the sent data, because I have to specify a baudrate for this, which is unknown to me. Which program is suitable to monitor the incoming data?
In Matlab I also have the same problem that I have to specify a baudrate for the com port.
My goal is to evaluate the data in Matlab. Preferably I would like to read the data directly with Matlab from the virtual com port and save it in Matlab. If this is not possible I would first save the data to a txt.file and then read it into Matlab.
Are there any ready-made solutions or open source programs for this?
Thanks for reading and your help!
I am studying a simple web server using c, and came up with some of these questions. How does IPv6 used in TCP? To use IPv6, do we have to use some form of modified version of TCP?? If we have to used the modified version of TCP, what do we have to change?? I think I read about Little Endian, as well as Big Endian, but I am not sure if there should be some special cases for IPv6.
As you'll probably be wanting the more gory details of the API changes, it's here: http://www.faqs.org/rfcs/rfc2553.html
Mostly it's a couple of longer address structures to pass in that can take a longer number and a new Family and Protocol name specified so the API can destiguish which struct you are using. Byte ordering is the same.
The actual TCP SYN, SYN/ACK, ACK stuff and all that is identical, it is literally a different IP layer frame with a longet number and other changes.
I create a module in kernel space that send a UPD segment using socket RAW, but my problem is read the UDP segment from kernel space.
I can read the UDP segment from user space, but when I prove to use "sock_recvmsg" from kernel space, I obtain as result -512
Please, help me!
I don't know why you feel the need to use a raw socket to send/recieve UDP - just use a UDP socket instead.
It may be that the structure you're supplying to sock_recvmsg for the address isn't right.
In general using networking from inside the kernel is a bad idea and should be avoided (not least, it ties your code to a specific kernel version). If you tell us what you're trying to do (ideally in the form of another question) maybe someone can suggest a better way.