✅ Correct way to pass data between threads?

FacePalmGamer · 2023-07-19T10:45:49.984Z

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 ```cs 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

S

sibber•7/19/23, 10:50 AM

gui framework usually provide a dispatcher

S

sibber•7/19/23, 10:50 AM

for winforms thats

Control.Invoke

Control.Invoke

Control.Invoke

Control.Invoke

F

FacePalmGamerOP•7/19/23, 10:53 AM

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

S

sibber•7/19/23, 10:54 AM

either would work

S

sibber•7/19/23, 10:54 AM

but id probably do that from the handler

F

FacePalmGamerOP•7/19/23, 10:55 AM

i was gonna say changing the handler function seems easier

F

FacePalmGamerOP•7/19/23, 11:04 AM

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;
}

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

F

FacePalmGamerOP•7/19/23, 11:07 AM

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?

C

cap5lut•7/19/23, 11:24 AM

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();
}

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

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

C

cap5lut•7/19/23, 11:27 AM

btw u dont need the delegate, u can simply use

Action<T>

Action<T>

Action<T>

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);
  }
}

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);
  }
}

Ccap5lut the ui thread has something like an internal list for delegates, which it will p...

F

FacePalmGamerOP•7/19/23, 11:29 AM

that makes sense.

Ccap5lut btw u dont need the delegate, u can simply use `Action<T>` for that and u should...

F

FacePalmGamerOP•7/19/23, 11:30 AM

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

C

cap5lut•7/19/23, 11:32 AM

hmmm, actually in this case probably not, as it should crash if the sender isnt a

SerialPort

SerialPort

SerialPort

SerialPort to show its a bug, i guess

C

cap5lut•7/19/23, 11:33 AM

or do the pattern matching and throw a more meaningful exception in the else branch

F

FacePalmGamerOP•7/19/23, 11:33 AM

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

C

cap5lut•7/19/23, 11:34 AM

yeah, u want to do the minimum amount of work on the ui thread

C

cap5lut•7/19/23, 11:34 AM

else it might freeze if there is too much going on

F

FacePalmGamerOP•7/19/23, 11:38 AM

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();
        }

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();
        }

F

FacePalmGamerOP•7/19/23, 11:39 AM

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

C

cap5lut•7/19/23, 11:45 AM

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

C

cap5lut•7/19/23, 11:50 AM

or maybe its fragmented because the connection died

C

cap5lut•7/19/23, 11:50 AM

such cases arent handled at all right now

F

FacePalmGamerOP•7/19/23, 11:51 AM

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

Ccap5lut tbh i have no clue about how serial ports work, the first thing that catches my ...

D

deprecatio•7/19/23, 11:53 AM

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

C

cap5lut•7/19/23, 11:53 AM

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

F

FacePalmGamerOP•7/19/23, 11:53 AM

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

C

cap5lut•7/19/23, 11:54 AM

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

F

FacePalmGamerOP•7/19/23, 11:54 AM

yeah

F

FacePalmGamerOP•7/19/23, 11:55 AM

I have a virtual serial port rn to test with

F

FacePalmGamerOP•7/19/23, 11:55 AM

It is just sending raw bytes

F

FacePalmGamerOP•7/19/23, 11:55 AM

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

C

cap5lut•7/19/23, 11:56 AM

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

Ccap5lut so its just stream based, so it it can be multiple and/or partial data at once

D

deprecatio•7/19/23, 11:56 AM

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

Ccap5lut do the picos send some kind of marker for an end of a message?

F

FacePalmGamerOP•7/19/23, 11:57 AM

no clue I am getting my picos tomorrow to start testing. I was planning on adding a separation byte incase i send longer messages

F

FacePalmGamerOP•7/19/23, 11:57 AM

that way i can just

data.split('~')

data.split('~')

data.split('~')

data.split('~')

D

deprecatio•7/19/23, 11:57 AM

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

F

FacePalmGamerOP•7/19/23, 11:58 AM

yeah thats too much work for a system that maybe will recieve 100 messages a second

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FacePalmGamerOP•7/19/23, 11:58 AM

i dont think i will be overflowing a pico or the serial communication line

D

deprecatio•7/19/23, 11:58 AM

what 1000/sec?

D

deprecatio•7/19/23, 11:58 AM

1000 bytes/sec you mean

F

FacePalmGamerOP•7/19/23, 11:59 AM

extra 0

F

FacePalmGamerOP•7/19/23, 11:59 AM

100/sec

F

FacePalmGamerOP•7/19/23, 11:59 AM

it could get around 20 or 30 updates from each tracker a second

F

FacePalmGamerOP•7/19/23, 11:59 AM

each tracker is sending 3 doubles

F

FacePalmGamerOP•7/19/23, 12:00 PM

so ~800 bytes

F

FacePalmGamerOP•7/19/23, 12:01 PM

its using 115200 baud so its good for 14400 bytes

D

deprecatio•7/19/23, 12:02 PM

baud is bit/s, not byte

F

FacePalmGamerOP•7/19/23, 12:02 PM

ah im still well over

D

deprecatio•7/19/23, 12:02 PM

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

C

cap5lut•7/19/23, 12:03 PM

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

✅ Correct way to pass data between threads?

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