I'm using VBA for Excel to communicate with hardware via serial communication. The code uses API calls similar to this here: http://dev.emcelettronica.com/serial-port-communication-in-excel-vba.
I've been successful with rs232 but it isn't working with rs485. After sending data and reading back the response, the read times out and it reads the same data that was sent.
I have access to software that someone else developed and their software works, so I know that the hardware is ok. I used a serial port sniffer and their code seems to have a lot of redundancy but it looks like its using the same configuration and sending the same data as my code. But their code gets a valid response while mine doesn't.
Could someone share some basic troubleshooting tips for this type of problem?
A major difference between rs232 and rs485 is that rs485 has an additional configuration setting for wire mode. The rs485 can support 2-wire or 4-wire configurations, with 3 different 2-wire configurations. Once I selected the correct configuration, the same code that I used for rs232 worked for rs485.
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I was able to make a working HID USB stack on my "StartUSB for PIC" board for the 18F2550 microcontroller. I based it on one of the MLA libraries, which was made for the 18F45K50 (MLA 2018_11_26, hid_custom, picdem_fs_usb_k50.x), but I converted it to work with the 18F2550 (there might have been easier ways, but only learned to work with PIC about 1 month ago). On the host side, I'm using LibUsbDotNet (also here, there might be easier ways - the documentation on this library really sucks) on a Windows 10 machine.
I'm using the HID class, full speed, and all seems to work. Although, I get some random errors on the host PC (see below), but doing one close/re-open cycle on the host side when getting the error is kind of solving it. Dirty, but it works. So I kind of ignore this now.
Win32Error:Win32Error:GetOverlappedResult Ep 0x01
995:The I/O operation has been aborted because of either a thread exit or an application request.
I'm not an expert on USB (yet). But all examples I'm seeing are based on 1) you send first a command to the device and 2) then you retrieve the answer from the device. I did some performance tests, and see that this indeed shows that I can do about 500 cycles/second. I think that is correct, because each cycle, sending command and retrieving answer, each takes 1 msec.
But do I really need to send a command? Can't I just keep reading endlessly, and when the device has somthing to say, it does send the data in an IN transaction, and when not it ignores which creates a timeout on the host side. That would mean that I can poll at 1000 cycles/second? Unfortunately, I have tried it by changing my implementation on the PIC, but I get very weird results. I think I have issues with suspend mode. That brings me to another question - how can I make the device get out of suspend mode (means that not the host, but the device should be triggering this event). I have searched the MLA library for command such as "wakeup", "resume", ... but couldn't find anything.
So, to summarize, 2 questions:
Conceptual: Can I send data from device to host without being requested for it by a command from the host?
For PIC experts: How can I have a device trigger for a wakeup from suspend mode?
And indeed, the answer is Yes on the first question.
In the meantime, I found another link on the web that contains a Visual Studio C# implementation of a USB library including all the source files.
If you're interested, this is the link
This C# host implementation works as a charm. Without sending a command to the device, I get notified immediately if a button is pressed. Great!
It also proofs that my earlier device implementation based on the original MicroChip MLA, is 100% correct. I stress tested the implementation by sending a "toggle LED command" as fast as I could, and I reach 1000 commands/second. Again great!
I think that LibUsbDotNet isn't that perfect after all. As I wrote above, I get rather unstable communication (Win32Error). But with this implementation, I don't get a single error, even after running for half an hour # 1000 commands/second.
So for me, case closed.
I have here a unit of King Pigeon S275 Remote Terminal Unit..
this RTU has communication modules for GSM, GPRS and TCP/IP (via RJ45 connection)
I can also communicate with this RTU by connecting it to my computer via USB .
The Manual I uploaded in this link...
https://www.mediafire.com/?gnfzfz5l7pess1p
This RTU can be configured using a configurator Software that is included in the purchase. By using that configurator software, you can also see the data/readings of all sensors connected to it, you can also see the status of all Digital Input/contacts connected to the RTU...
I have been researching about MODBUS the past days and I would like to create my own MODBUS program so that the S275 RTU can also send the sensors' data, or all the I/O data to my own program....
However ... I still do not know where I can start ...
Can I make this Modbus Program
1. using VB?
2. using PHP?
What other parameters do I need to know ?
and tutorials for making this modbus software...
I also uploaded here the S275's;
1. GPRS Custom Protocol
2. MODBUS TCP Handshake Communication Protocol
3. Register Address
https://www.mediafire.com/?khnfu53a4p12nrd
Thanks
PHP and ModBus sounds challenging. You want to control a serial port via PHP.
The easiest way is to get/purchase a library for ModBus/RTU.
Otherwise you have to implement the whole protocol by yourself from http://www.modbus.org/specs.php
You can use nmodbus API to add how reference in your VB or C# project.
There you have the manual.
Supports serial ASCII, serial RTU, serial over USB ASCII, serial over USB RTU, TCP, and UDP protocols.
These kinds of RTU’s are pretty inexpensive which means your greatest cost will be the time you will spend developing and debugging a driver. With that in mind I would first check if the RTU comes with its own OPC Server. Implementing an OPC client in C# or vb.net is very straight forward with plenty of code example out there. Some examples can be found here:
https://opcfoundation.org/developer-tools/developer-kits-unified-architecture/-net-stack-and-sample-applications/
If the RTU does not come with its own OPC server then, you can purchase a Modbus OPC Server from $900 to $2000 which will still be much more cost effective than writing and debugging your own driver and tends to be easier to setup. It will also significantly reduce the time to deliver your solution to your end customer which will be important if keep to project schedule is critical. I would check out, https://www.kepware.com/ and http://www.matrikonopc.com/
The other advantage of OPC is that it is a standardized interface which means should the RTU be replaced with a different model that supports a different protocol you would only have to purchase a new OPC server without the need to update your source code.
If the RTU does not have an OPC server or spending up to $2000 also not an option then there is plenty of open source implementations of the Modbus protocol, however implementation tends to be a bit more complex.
No problem, I used PHPModBus in several projects and it works like a charm!
This library supports Modbus TCP and UDP.
Try it, it is quite easy and straightforward.
I would like to use WinPCap library for "reliable" UDP receiving in my C++ application. All examples that I found, using this library for capturing and then proceding. Is there any way (example) how to configure PCap for streaming mode and receive UDP only and on uder defined port or how to solve this. In this time I have reliable UDP server able to receiving 0.5Gb/s. But on slower PC I have a packet lose I can see packets in ethereal but not in application.
thanks
vsm
I assume that you have already tried all of the more standard methods of increasing the number of datagrams that you are able to process? Things like increasing the recv buffer size, speeding up the processing that you do per datagram and using IOCP to allow you to bring more threads to bear on the problem or using RIO if you can target Windows 8?
If so then using WinPCap might work but it sounds like a bit of an extreme solution.
What you need to do is create a filter so that you only capture the datagrams that you are interested in... The docs include examples which use filters.
I have server from here: http://www.gamedev.net/topic/533159-article-using-udp-with-iocp/. This code working with IOCP. Its working fine on WIndows XP. There is no problem with receiving 0.5Gb/s. But now on Win7 is little unreliable. Sometimes there are packets positions error. (my device generating udp packets and in its payload there is PacketNumber - number increasing with each packet. When error occured i write all packet numbers into file. I can see for exmaple: 10,11,290,13,14... ). Is there any known differences in WinXP and Win7 for IOCP and multi threading? Or do you konw any free UDP server with IOCP processing?
In procedding loop I only adding packets into buffer and checking their numbers.
I know there are various programs that sniff packets like WireShark, but I'm pretty sure you can only view the data. I want to know if it's possible to edit incoming packets. I'm not sure if packets are the right term. I just want to edit incoming data that is recieved through the internet and who's destination is a specific application. Let's say I am playing an online game. As it loads my computer, it is recieving information like "This person has 10 coins in their money pouch". Obviously not exactly like that but you get the point. I would like to be able to change the data so it is say 100 instead of 10. I know something like this would be possible if you were to do this: Imagine my computer is connected to the internet with an ethernet cord. There is a device attached to the ethernet cord which recieves the data and changes it and then lets it continue to my computer. I would just like to know if this is possible, and how it could be accomplished.
Thanks!
The way I do it, is one of 2 ways:
1.
If your application supports it set up a HTTP Proxy on your machine and you could software like burp / Fiddler to mess with the data
If not (the protocol is not HTTP) you could use either one of 2 options i'v tried [Both based on Hooking the API calls from the application to the OS]:
EchoMirage software that allow messing around with the packets
[Bit more advanced: ] There is a debugger named OllyDbg which has a plugin named Universal Hooker; it enables to hook any window API function and execute a python script on demend. the uHooker contains examples for how to hook WSASend and WSARecive (which are the API functions used in windows sockets).
I'm writing a GUI-based app in VB.net that talks to a LambdaMOO server via telnet, sends commands to display the object hierarchy, then parses the output and creates a visual representation of the object hierarchy.
So my question is: is there some kind of "telnet client" class for .NET to simplify the sending and receiving of data, or do I have to write my own using the socket API?
Does Mono have something like this?
Barring an easy solution, does anyone have a good tutorial they can point to for telnet client programming in VB.net?
Ok, I had a similar issue and ignoring all security complications and the like, wanted to TELNET from a VB initiated connection to a remote device and do stuff. I concur that the whole negotiation process is a hellish thing to do but once you've worked it out it's actually pretty simple to implement. I decided not to stop because I kept reading things that said it couldn't be done when it clearly can be done if you can write and read 1's and 0's into/from a network stream.
The code in the link below will initiate the connection and get you through to actually exchanging clear text information over TELNET. Given the example of sending a username and password combo shows how to read and write to the connection.
Big tips - initially have a nice big textbox or something to trap everything that comes into the buffer (variable returndata). This will help you diagnose problems. Also check on my blog there how to do this without the textbox blinking like a flashing thing. Once you've done all that and you know your script is reliable, trun off any screen updates and it will whizz through rather than take an age.
Apologies for the really dirty code and the crappy website layout.
http://myhead-online.blogspot.com/2009/05/vb-net2008-express-telnet-to-sun.html
The telnet protocol is basically just the usual TCP protocol, with a bunch of optional stuff that you probably won't need to implement. So you'd open a socket and start sending and receiving data with the socket stream interface.
Give it a try with the regular socket API, you'll probably find that it's quite straightforward.
just a suggestion. you may try to program your vb application to execute an existing telnet application in batch mode.
here is the link for your reference. refer to 7.3 Using Plink in batch files and scripts. Hope it helps.
You can grab one of any number of libraries to use. Here's one library:
LINK
For others try googling something along the lines of: library telnet mud .NET
Lastly, there are any number of opensource MUD/MOO/MUSH projects open at any time who are willing the share ideas and looking for people to help with projects.
I had my trials with telnet. You've to use tools like wireshark in conjuntion to figure out what commands needs to be initiated. I did find communicating with my unix box quite a challenge. For one thing you must know your telnet instructions. You might find it difficult to determined the state of the application - whether it is logged in or not innately. You'd have to formulate your own logic for it.
Another thing you'd have to do is parse the bytes returned by telnet into commands or instruction data i.e. you have to know if the bytes received is an instruction or some other thing it is trying to send you. Here is a ref that would come in handy.
First I suggest you start using the wireshark tool and get the communications send to and fro manually as well as via application.
From the LambdaMOO end of things, if you have wizard access or are friends with someone who does, you can have the MOO give you the data over another protocol that you might be able to work with more readily, such as HTTP. All you need is an object on the MOO with a do_login_command() set to handle requests, and then use the listen() builtin to get that object to listen on a given port. As long as a protocol doesn't require anything complex SSL, it's fairly easy to code up on the MOO end. So that might be worthwhile if VB.net has easier handling for HTTP etc.