COM port send/receive
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Hi all, I am communicating to a COM port where I send a string to the device and it returns a string. A button event triggers a string to be written and a text box is populated with the read value. What I ultimately am trying to do is to have the text box automatically update with the returned value from the device. I initially thought a timer event should be employed, but I'm not sure if this would be the most robust way to do this. Thanks.
The same TextBox? What if the user is typing in it when the result comes along? I would wrap the serial port in a class that provides an event for response and update the TextBox when the event fires. (Being me, I'd write a class that I can use with my CommScript[^].) If it's one TextBox, I might also disable the TextBox and Button when the Button is clicked, and re-enable them when the event fires.
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The same TextBox? What if the user is typing in it when the result comes along? I would wrap the serial port in a class that provides an event for response and update the TextBox when the event fires. (Being me, I'd write a class that I can use with my CommScript[^].) If it's one TextBox, I might also disable the TextBox and Button when the Button is clicked, and re-enable them when the event fires.
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I'll be using a label instead. Sorry for the confusion. Presently there is a text box, but I won't be allowing text input in the application. The device will require that a string be written to it as it doesn't transmit continuously.
Well, at least this gives me an excuse to write a SerialCommunicator... :sigh:
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Well, at least this gives me an excuse to write a SerialCommunicator... :sigh:
I have pasted below the code that I am now using. As I am new to this, I thought a timer could be relatively easy to implement instead of the btnStart_Click event. Also, I know timing could really mess things up, but not sure how to deal with that either...
private void btnStart_Click(object sender, EventArgs e)
{
//Makes sure serial port is open before trying to write
try
{
if (!sp1.IsOpen)
sp1.Open();sp1.Write("\*X01\\r"); } catch (Exception ex) { MessageBox.Show("Error opening/writing to serial port :: " + ex.Message, "Error!"); } } private void Form1\_Load(object sender, EventArgs e) { // all of the options for a serial device // can be sent through the constructor of the SerialPort class // PortName = "COM1", Baud Rate = 9600, Parity = odd, // Data Bits = 7, Stop Bits = One, Handshake = None sp1 = new SerialPort("COM1", 9600, Parity.Odd, 7, StopBits.One); sp1.Handshake = Handshake.None; sp1.DataReceived += new SerialDataReceivedEventHandler(sp\_DataReceived); sp1.ReadTimeout = 500; sp1.WriteTimeout = 500; sp1.Open(); } void sp\_DataReceived(object sender, SerialDataReceivedEventArgs e) { Thread.Sleep(100); string data = sp1.ReadExisting(); this.BeginInvoke(new SetTextDeleg(si\_DataReceived), new object\[\] { data }); } private void si\_DataReceived(string data) { char\[\] charsToTrim = {'X','0','1'}; textBox1.Text = data.TrimStart(charsToTrim); } -
I have pasted below the code that I am now using. As I am new to this, I thought a timer could be relatively easy to implement instead of the btnStart_Click event. Also, I know timing could really mess things up, but not sure how to deal with that either...
private void btnStart_Click(object sender, EventArgs e)
{
//Makes sure serial port is open before trying to write
try
{
if (!sp1.IsOpen)
sp1.Open();sp1.Write("\*X01\\r"); } catch (Exception ex) { MessageBox.Show("Error opening/writing to serial port :: " + ex.Message, "Error!"); } } private void Form1\_Load(object sender, EventArgs e) { // all of the options for a serial device // can be sent through the constructor of the SerialPort class // PortName = "COM1", Baud Rate = 9600, Parity = odd, // Data Bits = 7, Stop Bits = One, Handshake = None sp1 = new SerialPort("COM1", 9600, Parity.Odd, 7, StopBits.One); sp1.Handshake = Handshake.None; sp1.DataReceived += new SerialDataReceivedEventHandler(sp\_DataReceived); sp1.ReadTimeout = 500; sp1.WriteTimeout = 500; sp1.Open(); } void sp\_DataReceived(object sender, SerialDataReceivedEventArgs e) { Thread.Sleep(100); string data = sp1.ReadExisting(); this.BeginInvoke(new SetTextDeleg(si\_DataReceived), new object\[\] { data }); } private void si\_DataReceived(string data) { char\[\] charsToTrim = {'X','0','1'}; textBox1.Text = data.TrimStart(charsToTrim); }If it's woking that way, then leave it alone. But now I'm confused as to what you're writing and how.
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If it's woking that way, then leave it alone. But now I'm confused as to what you're writing and how.
The device I am using (a Newport meter) requires a string *X01\r in order to return the value that is on the display. When the button is clicked, it writes that string to the com port and then returns a series of characters, some of which are the actual value on the display. The problem is the button needs to be clicked. I want to have a start button and a stop button that begins and ends a thread used for automatically reading and writing to the com port, displaying the read value in a form label. Since I'm just learning C#, this is not an easy task. If anyone has any pointers, that would be greatly appreciated. Thanks,Mike
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The device I am using (a Newport meter) requires a string *X01\r in order to return the value that is on the display. When the button is clicked, it writes that string to the com port and then returns a series of characters, some of which are the actual value on the display. The problem is the button needs to be clicked. I want to have a start button and a stop button that begins and ends a thread used for automatically reading and writing to the com port, displaying the read value in a form label. Since I'm just learning C#, this is not an easy task. If anyone has any pointers, that would be greatly appreciated. Thanks,Mike
I would likely use a System.Timers.Timer; the Elapsed event handler would handle the writing, the code you have above would deal with the incoming data.
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I would likely use a System.Timers.Timer; the Elapsed event handler would handle the writing, the code you have above would deal with the incoming data.
I tried that without success. If I move the button click event to a timer tick event, nothing happens. I have even set the timer tick time to be >>Timer.Sleep (100) to make sure that there are no timing issues, but still nothing happens. However, if it did "work", seems that there would be a better way than a Timer.Sleep method....., but I'd take a successful timer function, if it would work. Thoughts?
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Hi all, I am communicating to a COM port where I send a string to the device and it returns a string. A button event triggers a string to be written and a text box is populated with the read value. What I ultimately am trying to do is to have the text box automatically update with the returned value from the device. I initially thought a timer event should be employed, but I'm not sure if this would be the most robust way to do this. Thanks.
why are you going for timer to read the comport buffer, i used stopwatch for this one , see the below code this may help u
Stopwatch ObjStopWatch = new Stopwatch();
ObjStopWatch.Start();
long StDelay = ObjStopWatch.ElapsedMilliseconds;
try
{
string FromModem = "";
Comport.ClearInputBuffer();
Comport.Write(Command);
Comport.Write(new byte[] { 0x0D, 0x0A });
do
{
if (Comport.InBufferCount>0)
{
Comport.Read(Comport.InBufferCount);
FromModem += Comport.InputStreamString;
if (FromModem.Contains("OK"))
break;
}
} while ((StDelay + 5000) > ObjStopWatch.ElapsedMilliseconds);Frommodem holds the value of the comport buffer. here my timeout is 5000 milliseconds.. Thanks
Rajesh B --> A Poor Workman Blames His Tools <--
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I tried that without success. If I move the button click event to a timer tick event, nothing happens. I have even set the timer tick time to be >>Timer.Sleep (100) to make sure that there are no timing issues, but still nothing happens. However, if it did "work", seems that there would be a better way than a Timer.Sleep method....., but I'd take a successful timer function, if it would work. Thoughts?
I've never had trouble with timers. You start the timer? And set it to AutoReset? Does it elapse at least once?
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I've never had trouble with timers. You start the timer? And set it to AutoReset? Does it elapse at least once?
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:~ I checked the timer again.....Would help if it were enabled. Sometimes I wonder. Seems that a stopwatch, as Rajesh suggest, may be the better way to handle this?
mprice214 wrote:
enabled
Yes, but that's what Start does anyway. I prefer the Timer Elapsed handler for sending and the event handler for receiving.
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why are you going for timer to read the comport buffer, i used stopwatch for this one , see the below code this may help u
Stopwatch ObjStopWatch = new Stopwatch();
ObjStopWatch.Start();
long StDelay = ObjStopWatch.ElapsedMilliseconds;
try
{
string FromModem = "";
Comport.ClearInputBuffer();
Comport.Write(Command);
Comport.Write(new byte[] { 0x0D, 0x0A });
do
{
if (Comport.InBufferCount>0)
{
Comport.Read(Comport.InBufferCount);
FromModem += Comport.InputStreamString;
if (FromModem.Contains("OK"))
break;
}
} while ((StDelay + 5000) > ObjStopWatch.ElapsedMilliseconds);Frommodem holds the value of the comport buffer. here my timeout is 5000 milliseconds.. Thanks
Rajesh B --> A Poor Workman Blames His Tools <--
Hi Rajesh, The issue I'm now having is that using a timer doesn't seem to be the most deterministic approach. In other words, I have a string that is written to the device at certain intervals. The serial data received method (SerialDataReceivedEventArgs) then Invokes the function that writes the returned string to a text box. However, to make sure the entire string is sitting in the buffer to be read, there is the Thread.Sleep. This seems very ineffecient and I'm trying to verify if that assumption is correct. What I would like to do is to write and read as fast as possible without the thread getting all tied up with timing issues. The device I'm talking to sends a carriage return at the end of the string. It seems that the fastest way to do this would be if I have a loop that writes a command string/waits for the string ending with a cr/writes that read value to whatever (textbox, etc) and writes the command string again. Since I am new to this, I'm not sure if the stopwatch is the way to go, but I think a timer/thread.sleep combination is asking for crashing problems when I'm trying to do this a fast as possible. Thoughts?
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Hi Rajesh, The issue I'm now having is that using a timer doesn't seem to be the most deterministic approach. In other words, I have a string that is written to the device at certain intervals. The serial data received method (SerialDataReceivedEventArgs) then Invokes the function that writes the returned string to a text box. However, to make sure the entire string is sitting in the buffer to be read, there is the Thread.Sleep. This seems very ineffecient and I'm trying to verify if that assumption is correct. What I would like to do is to write and read as fast as possible without the thread getting all tied up with timing issues. The device I'm talking to sends a carriage return at the end of the string. It seems that the fastest way to do this would be if I have a loop that writes a command string/waits for the string ending with a cr/writes that read value to whatever (textbox, etc) and writes the command string again. Since I am new to this, I'm not sure if the stopwatch is the way to go, but I think a timer/thread.sleep combination is asking for crashing problems when I'm trying to do this a fast as possible. Thoughts?
Here is what I have:
private void DisplayText(object sender, EventArgs e) { textBox1.Text = RxString; serialPort1.DiscardInBuffer(); while (serialPort1.BytesToRead == 0) serialPort1.WriteLine("\*X01\\r"); } private void serialPort1\_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) { RxString = ""; try { RxString = serialPort1.ReadTo("\\r"); } catch (Exception Exception) { return; } this.Invoke(new EventHandler(DisplayText)); } private void textBox1\_TextChanged(object sender, EventArgs e) { } private void timer1\_Tick(object sender, EventArgs e) { //timer1.Interval = 50; //if (!serialPort1.IsOpen) return; //serialPort1.WriteLine("\*X01\\r"); }I want to get rid of the timer and have a while loop that writes the ("*X01\r") once the buffer is empty. Then I won't need the timer. However, I can't get a while loop to work.