Topics

C#•17mo ago

✅ Correct way to pass data between threads?

I have an event on a simple Winform reading from the serial port. The issue is I would like to output the data onto a winform component, but because its on an even it happens on a different thread and I get the error

Cross-thread operation not valid: Control 'textBoxRecieve' accessed from a thread other than the thread it was created on.

so what is the correct way to pass this data? I know I could do something like a channel do make a cross thread communication system, but that seems excessive and I figure there is an easier way I do now know

public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
        {
            textBoxRecieve.Text = textBoxRecieve.Text + Environment.NewLine + ((SerialPort)sender).ReadExisting();
        }

public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
        {
            textBoxRecieve.Text = textBoxRecieve.Text + Environment.NewLine + ((SerialPort)sender).ReadExisting();
        }

That was the function running and erroring. I was just trying to make a simple ECHO test debugListen.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler); and that is how I was setting up the event

51 Replies

sibber•17mo ago

gui framework usually provide a dispatcher for winforms thats Control.Invoke

FacePalmGamerOP•17mo ago

Am i changing my event to be called from the invoker or am I adding the invoke method to my handler function? not really sure how this works so just trying to understand

sibber•17mo ago

either would work but id probably do that from the handler

FacePalmGamerOP•17mo ago

i was gonna say changing the handler function seems easier

private delegate void DELEGATE(string data);

public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
  Delegate del = new DELEGATE(ProcessData);
  this.Invoke(del, (((SerialPort)sender).ReadExisting()));
}

private void ProcessData(string data)
{
  textBoxRecieve.Text = textBoxRecieve.Text + Environment.NewLine + data;
}

private delegate void DELEGATE(string data);

public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
  Delegate del = new DELEGATE(ProcessData);
  this.Invoke(del, (((SerialPort)sender).ReadExisting()));
}

private void ProcessData(string data)
{
  textBoxRecieve.Text = textBoxRecieve.Text + Environment.NewLine + data;
}

This works. Thank you. Posting code incase anyone else finds this later I do have a question. how does the Invoke method work? Is it telling the main thread to pause what its doing and run this code now? or is it some other way?

cap5lut•17mo ago

the ui thread has something like an internal list for delegates, which it will process on each iteration. basically something like

while (isRunning)
{
  processInvocations();
  processEvents();
  renderUI();
}

while (isRunning)
{
  processInvocations();
  processEvents();
  renderUI();
}

btw u dont need the delegate, u can simply use Action<T> for that and u should prepare the data in ur handler and only pass that then:

public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
  if (sender is SerialPort port)
  {
    string data = port.ReadExisting();
    this.Invoke(ProcessData, data);
  }
}

public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
  if (sender is SerialPort port)
  {
    string data = port.ReadExisting();
    this.Invoke(ProcessData, data);
  }
}

FacePalmGamerOP•17mo ago

that makes sense. is there a reason to do the if() instead of just casting it? shouldnt it always be a SerialPort

cap5lut•17mo ago

hmmm, actually in this case probably not, as it should crash if the sender isnt a SerialPort to show its a bug, i guess or do the pattern matching and throw a more meaningful exception in the else branch

FacePalmGamerOP•17mo ago

also im guessing I should prepare data before i use it since its on its own thread already?

cap5lut•17mo ago

yeah, u want to do the minimum amount of work on the ui thread else it might freeze if there is too much going on

FacePalmGamerOP•17mo ago

ok this is a bit off topic, but im not sure if there is a better way to do this. Is there a better way to identify data coming from the serial port? Currently im just sending formated strings and parsing them

public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
        {
            string data = ((SerialPort)sender).ReadExisting();
            string dataG = data;
            string keyItem = data.Substring(0, data.IndexOf(' '));
            data = data.Substring(data.IndexOf(' ') + 1);
            string keyType = data.Substring(0, data.IndexOf(' '));
            data = data.Substring(data.IndexOf(' ') + 1);
            double value = double.Parse(data);
            switch (keyItem)
            {
                case "mobile1":
                    if (keyType == "lat")
                        RCRGroundStation.mobilePosition[1].Item1 = value;
                    else if (keyType == "lon")
                        RCRGroundStation.mobilePosition[1].Item2 = value;
                    break;
                case "baseStation":
                    if (keyType == "lat")
                        RCRGroundStation.basePosition.Item1 = value;
                    else if (keyType == "lon")
                        RCRGroundStation.basePosition.Item2 = value;
                    break;
                case "rocket":
                    if (keyType == "lat")
                        RCRGroundStation.rocketPosition.Item1 = value;
                    else if (keyType == "lon")
                        RCRGroundStation.rocketPosition.Item2 = value;
                    break;
            }
            this.Invoke(ProcessData, dataG);
        }

        private void ProcessData(string data)
        {
            textBoxRecieve.Text = textBoxRecieve.Text + data;

            main.UpdateCords();
        }

public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
        {
            string data = ((SerialPort)sender).ReadExisting();
            string dataG = data;
            string keyItem = data.Substring(0, data.IndexOf(' '));
            data = data.Substring(data.IndexOf(' ') + 1);
            string keyType = data.Substring(0, data.IndexOf(' '));
            data = data.Substring(data.IndexOf(' ') + 1);
            double value = double.Parse(data);
            switch (keyItem)
            {
                case "mobile1":
                    if (keyType == "lat")
                        RCRGroundStation.mobilePosition[1].Item1 = value;
                    else if (keyType == "lon")
                        RCRGroundStation.mobilePosition[1].Item2 = value;
                    break;
                case "baseStation":
                    if (keyType == "lat")
                        RCRGroundStation.basePosition.Item1 = value;
                    else if (keyType == "lon")
                        RCRGroundStation.basePosition.Item2 = value;
                    break;
                case "rocket":
                    if (keyType == "lat")
                        RCRGroundStation.rocketPosition.Item1 = value;
                    else if (keyType == "lon")
                        RCRGroundStation.rocketPosition.Item2 = value;
                    break;
            }
            this.Invoke(ProcessData, dataG);
        }

        private void ProcessData(string data)
        {
            textBoxRecieve.Text = textBoxRecieve.Text + data;

            main.UpdateCords();
        }

btw thanks for all the help this makes alot more sense now. Thought i would ask this question though since there might be a better way to do communication

cap5lut•17mo ago

tbh i have no clue about how serial ports work, the first thing that catches my eye is the question if the data is always one complete message, or if it could also be multiple messages at once or even fragmented messages or maybe its fragmented because the connection died such cases arent handled at all right now

FacePalmGamerOP•17mo ago

thats very true. but that would be handled on the slave device This is for a system of pi picos talking with each other making a tracking system for a rocket. this UI is for a ground station so that handling would be for the pico attached to it to group the message, but you are right I should still add a catch incase a message fragments

Omnissiah•17mo ago

serial port doesn't have the concept of message, it's just data although there are some settings that can influence this

cap5lut•17mo ago

the parsing itself could be done via regex as well, would be a bit cleaner

FacePalmGamerOP•17mo ago

I have done next to 0 work with regex. I know it exists and i have used it in path of exile(a game) and thats it

cap5lut•17mo ago

so its just stream based, so it it can be multiple and/or partial data at once

FacePalmGamerOP•17mo ago

yeah I have a virtual serial port rn to test with

FacePalmGamerOP•17mo ago

It is just sending raw bytes

FacePalmGamerOP•17mo ago

as it recieves them it puts them in the next port (in the case of my virtual com)

cap5lut•17mo ago

do the picos send some kind of marker for an end of a message?

Omnissiah•17mo ago

yes, from the pov of c# it's the usual stream reader, so you say read 2000 bytes or even read 1 byte and when it's ready it returns that to you

FacePalmGamerOP•17mo ago

no clue I am getting my picos tomorrow to start testing. I was planning on adding a separation byte incase i send longer messages that way i can just data.split('~')

Omnissiah•17mo ago

you could search if pico offers flow control settings or something but in the end who cares

FacePalmGamerOP•17mo ago

yeah thats too much work for a system that maybe will recieve 100 messages a second i dont think i will be overflowing a pico or the serial communication line

Omnissiah•17mo ago

what 1000/sec? 1000 bytes/sec you mean

FacePalmGamerOP•17mo ago

extra 0 100/sec it could get around 20 or 30 updates from each tracker a second each tracker is sending 3 doubles so ~800 bytes its using 115200 baud so its good for 14400 bytes

Omnissiah•17mo ago

baud is bit/s, not byte

FacePalmGamerOP•17mo ago

ah im still well over

Omnissiah•17mo ago

eh you know it's still relatively busy for a serial

cap5lut•17mo ago

u know this would be a lot easier if the protocol would be binary instead of text based 😂

FacePalmGamerOP•17mo ago

thats what testing is for.

Omnissiah•17mo ago

are you sure? binary could be a mess text is somewhat easier

FacePalmGamerOP•17mo ago

this guy just wants to use bit banging for everything

cap5lut•17mo ago

why would it be a mess? i would say its a lot easier, the only real trap would be difference in endianness, which can be easily covered

FacePalmGamerOP•17mo ago

I believe on the lower level serial is just hex so its not too different. its just readable

Omnissiah•17mo ago

text is easier because human understandable and debuggable almost every protocol i met was text based

FacePalmGamerOP•17mo ago

SPI is not i believe

Omnissiah•17mo ago

probably it's like that because it's meant to be operated by a console or somethings

FacePalmGamerOP•17mo ago

i2c is also only hex i believe but i dont know enough about them to advocate one way or another

Omnissiah•17mo ago

iot for home automation is text

FacePalmGamerOP•17mo ago

what protocol does home automation use?

Omnissiah•17mo ago

openwebnet is one of them

FacePalmGamerOP•17mo ago

well it makes sense. Alot of that data is probably outputting to the user so sending strings and chars vs hex makes sense

Omnissiah•17mo ago

i don't exactly know what made them take this route

FacePalmGamerOP•17mo ago

well this derailed quite a bit form the original question. Thanks for all the help, I'll look into different ways to parse and setup my communication network

cap5lut•17mo ago

good luck 😄 also please dont forget to $close the thread (if u have questions later it would be better to open a new thread anyway)

MODiX•17mo ago

Use the /close command to mark a forum thread as answered

Omnissiah•17mo ago

to me if you have that amout of updates you could use a queue (buffer) between serial and ui just that

FacePalmGamerOP•17mo ago

wouldnt really be a queue. because I want the newest information as soon as possible. If im getting too many inputs I just throwout the ones i miss will do If i need to throttle it. i just ignore inputs read the newest ones and disregard the rest

Omnissiah•17mo ago

sure sure, i was just thinking on how to do this in a non async/await architecture you would still need a timeout for the response from the form/controls

FacePalmGamerOP•17mo ago

ah i see. Well the input for this is a pi pico, the pico only runs C so it will be bare bones. I believe any modern laptop should be able to handle the through put of a pi, but i could be wrong the pi is the place where i except a bottleneck to be if there even is one Aight ima close this now. I have to go to work. Ty for the help

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