Controlled reading from serial port

I'm trying to establish a connection to an external device through the serial port. This is done in a while-loop which sends an association request tries to get a response if a response is not recieved a new rewuest is sent, etc. At the moment this procedure does not work. I am considering two explanations for this. The first is that the loop does not wait long enough for a response to come and simply keeps pumping out requests, the other is that there is something wrong with the reading algorithm, that doesn't let it properly take in information from the serial port.
Solved!
Go to Solution.
Attachments:
association_loop.GIF ‏5 KB
read_visa.GIF ‏8 KB

I made a new version of the read case. The old version was a while loop, the new version is a while loop which will go on until it encounters an EOF character. In this case it is
0xC1 or 'Á'. I thought the old version would break before getting any message. This doesnt get any signal either. I have probed it, and it doesn't get a string from which to take the length.
Attachments:
read_visa2.GIF ‏10 KB

Similar Messages

A problem about reading from serial port

Hi,
I just sent '0x03' from MCU to PC continuously, and then sent '/n' as a stop character after every '0x03'. I use labview to read the data. The problem is when it get two '03' it get a '0', another two '03' and another a '0'. I don't know where is the '0' from?
PS: Hyper terminal can display natrually.
Thank you!
帖子被hengfo在08-08-2007 10:14 PM时编辑过了
Attachments:
serial read.vi ‏36 KB

I think the problem may be the loop reading the serial port is running too fast. There is no timing delay in the loop, so you are reading it as fast as you can, and probably faster than the device is sending data. So sometimes the buffer is empty, and then the empty string gets converted to a numeric zero. The way to know for sure is to put an indicator on the error wire coming out of the serial port read. I bet you will see errors about the read buffer being empty.
Put a wait timer in the loop to slow down the execution just slightly. This is a good idea so that LV doesn't eat up all the CPU resources. Look at the example for Basic Serial Write and Read. You may want to have a loop ahead of the read that waits until there are a certain number of bytes at the port before it reads the serial port. You may want to put a loop around the serial port that waits until a valid number is read in before it exits the loop and goes to the numeric conversion.
Message Edited by Ravens Fan on 08-09-2007 08:50 AM

Computer freezes while reading from serial port

My computer freezes when i tried to read from a serial port for a longer period of time such as 10 hours. I always close the serial port after reading. please, help me solve this problem

I too experienced a similar problem twice on my machine and I have no idea how to stop it because it is so intermittent and I cannot replicate it.
Perhaps I can offer some clues.
The Labview screen cannot be stopped and some parts of Windows appears frozen. Oddly enough I can switch to the block diagram but thats about all I can do. The LV stop button will indicate a mouse click on it but the VI does not stop. iT also cannot be closed.
Even the reset button and power button on the PC does not work. I am forced to power down the PC (pull the plug) to get back control.
I believe it is related to a visa call to my serial Balance.
ANyway no solution but hopefully some clues.
Dell Optiplex GX260 w/ 500MB RAM
Win2K 500.2195 w service pak 4,
NI
serial Hardware and NI serial ver1.45 (16 com ports)
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Efficient optimized way to read from serial port and GPS data display using map

Hi,
I have a custom h/w which reads the data from GPS Rx and after parsing send it to PC over RS232.
Each second it sends 201 bytes to PC. I have developed a VI to read the GPS data and display it. Project file is attached.
Fulctionality of different loops are as following:
1. LOOP 1: 1.1 Reads the serial data from com port.
               1.2 Synclonize the frame using start bytes "a" and "z".
               1.3 Reads next 4 bytes containg receiving error information.
               1.4 Reads next 195 bytes. in which initial 80 byes are GPS data. rest are others.
2. LOOP 2: 2.1 Extarcts the GPS information and put them in an array.
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3. LOOP 3:3: 3.1 Displays the GPS data in chart and log the data in a file.
4. FLOW : Uses the GMAP .NET based API to creat a MAP and display.
Problem statement:
1. Functionality acheived.
2. However in between data set is being missed by the programm.
Quesitions:
1. Is the developed VI is efficient in terms of using queue loacl variables etc.
2. What are the improvments I can do to solve the problem.
Any other suggestions|
Thank you
jayant
jayant
Attachments:
Telemetry_Receiver_v2.zip ‏3075 KB

One of the most common problems in serial communication is the need for an adequate timing: how much time is expected your device to spend before answering? Have you put and adequate pause in your code before reading from the serial port?
Hope this helps
Roberto
Proud to use LW/CVI from 3.1 on.
My contributions to the Developer Zone Community
If I have helped you, why not giving me a kudos?

Plot more than one analog value to a waveform chart by reading from Serial Port

I have 4 LDRs and I want to plot their values to a waveform chart by reading them from the serial port. I have looked around and found an example of a VI plotting one value to a waveform chart (attached below) but I am unsure about how to expand this for 4 different waveforms, mostly because I don't particularly understand the way is being read currently. If someone could either point me in the way of a relevant example or explain/show me a solution, or explain howthe current VI I have works, that would be greatly appreciated.
Attachments:
LDRread.vi ‏20 KB

Since I assume each LDR (whatever that is) has its own serial connection, you will need to read from 4 different serial ports. From there, just form an array of all the data and write to the chart.
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Function for reading from serial port

Hi experts,
We are trying to read data from the serial port with the following function we got from internet.
The problem is when creating the object with the sentence CREATE OBJECT o_obj '"MSCOMMLib.MSComm.1"'.
This returns a sy-subrc = 2 and shows the exception NO_CREATE_OBJECT.
We already copied the file MSCOMM32.OCX in c:\windows\system32 and we successfuly registered it, with regsvr32.exe.
We tried it with Windows XP and Vista.
Anybody has any idea?
Thanks in advance
FUNCTION ZSERIALCOM.
""Interfase local
*" IMPORTING
*"     REFERENCE(MODE) TYPE I DEFAULT 0
*"     REFERENCE(COMMPORT) TYPE I DEFAULT 1
*"     REFERENCE(SETTINGS) TYPE C DEFAULT '2400,N,8,1'
*"     REFERENCE(OUTPUT) TYPE C OPTIONAL
*" EXPORTING
*"     REFERENCE(INPUT) TYPE C
*" EXCEPTIONS
*"      NO_CREATE_OBJECT
TYPE-POOLS: sabc.
INCLUDE ole2incl.
PERFORM init.
PERFORM open_port USING commport settings.
IF mode = 0.
    PERFORM read_port
    CHANGING input.
ENDIF.
IF mode = 1.
    PERFORM write_port
    USING output
    CHANGING input.
ENDIF.
PERFORM final.
ENDFUNCTION.
DATA: o_obj TYPE ole2_object.
*& Form Init
text
--> p1 text
<-- p2 text
FORM init.
DATA:
wa_repid LIKE sy-repid.
wa_repid = sy-repid.
CALL FUNCTION 'AUTHORITY_CHECK_OLE'
EXPORTING
program = wa_repid
activity = sabc_act_call
application = 'MSCOMMLib.MSComm.1'
EXCEPTIONS
no_authority = 1
activity_unknown = 2
OTHERS = 3.
IF sy-subrc <> 0.
MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
ENDIF.
CREATE OBJECT o_obj '"MSCOMMLib.MSComm.1"'.
IF sy-subrc <> 0.
RAISE no_create_object.
ENDIF.
ENDFORM. " Init
FORM open_port *
--> COMMPORT *
--> SETTINGS *
FORM open_port USING commport settings.
SET PROPERTY OF o_obj 'CommPort' = commport.
SET PROPERTY OF o_obj 'Settings' = settings.
SET PROPERTY OF o_obj 'InputLen' = 0.
SET PROPERTY OF o_obj 'PortOpen' = 1.
ENDFORM. "open_port
FORM read_port *
--> INPUT *
FORM read_port
CHANGING input.
DATA:
wa_buffer TYPE i.
DO 10 TIMES.
GET PROPERTY OF o_obj 'InBufferCount' = wa_buffer.
IF wa_buffer > 0.
GET PROPERTY OF o_obj 'Input' = input.
EXIT.
ENDIF.
ENDDO.
ENDFORM. " read_port
FORM write_port *
--> OUTPUT *
FORM write_port
USING output
CHANGING input.
DATA:
wa_buffer TYPE i.
SET PROPERTY OF o_obj 'Output' = output.
DO 10 TIMES.
GET PROPERTY OF o_obj 'InBufferCount' = wa_buffer.
IF wa_buffer > 0.
GET PROPERTY OF o_obj 'Input' = input.
EXIT.
ENDIF.
ENDDO.
ENDFORM.
*& Form final
text
--> p1 text
<-- p2 text
FORM final.
SET PROPERTY OF o_obj 'PortOpen' = 0.
FREE OBJECT o_obj.
ENDFORM. " finalbligw

Hi ,
I want to read value form weigh bridge through COMM port. I have developed the FM and done the setting as mentioned in the below link
Read COMM port using ABAP w/o third party software
but while executing the FM independently I am able to get the value from the COMM port,but when I call the FM from a program I am not able to get the output value from the FM.I am calling the FM from the report program.please find the code below.
report test.
data : lv_input TYPE c.
CALL FUNCTION 'ZFM_WEIGHINTERFACE'
EXPORTING
    MODE                         = 0
    COMMPORT               = 1
    SETTINGS                  = '1200,N,8,1'
    OUTPUT                     = ''
IMPORTING
    INPUT                        = lv_input
EXCEPTIONS
    NO_CREATE_OBJECT       = 1
    OTHERS                 = 2
IF SY-SUBRC <> 0.
* Implement suitable error handling here
ENDIF.
if I execute the FM independently the output is getting perfectly.but while calling from a program i am facing the issue..
any suggestion is appreciated.
Thanks
Vivek

Reading from serial port

HI,
I need to read data from virtual serial (rfcomm - BT GPS receiver). I connect to my gps using system command:
[root@localhost ~]# rfcomm connect /dev/rfcomm0 XX:XX:XX:XX:XX:XX
and this creates port at /dev/rfcomm0, when I do :
[root@localhost ~]# cat /dev/rfcomm0
I get:
M,0.0,0000*76
$GPGSA,A,1,,,,,,,,,,,,,50.0,50.0,50.0*05
$GPRMC,000009.999,V,0000.0000,N,00000.0000,E,,,101102,,*17
$GPGGA,000010.999,0000.0000,N,00000.0000,E,0,00,50.0,0.0,M,0.0,M,0.0,0000*7E
$GPGSA,A,1,,,,,,,,,,,,,50.0,50.0,50.0*05
and the only problem is what to do to read this sequences via java application. I obtained package comm2.0.3.zip , but have no idea what next. I would be grateful for any help.
best regards
joshua

I did everything described here:
http://www.geeksville.com/~kevinh/linuxcomm.html
got an example from:
http://java.sun.com/developer/releases/javacomm/SimpleRead.java
(the defaultPort = "/dev/term/a"
replaced with
defaultPort = "/dev/rfcomm0")
i connect to my gps with:
[root@localhost ~]# rfcomm connect /dev/rfcomm0 XX:XX:XX:XX:XX:XX
start the application and get an error:
java.io.IOException: Error instantiating class gnu.io.RXTXCommDriver
gnu.io.RXTXCommDriver cannot be cast to javax.comm.CommDriver
at javax.comm.CommPortIdentifier.loadDriver(CommPortIdentifier.java:239)
at javax.comm.CommPortIdentifier.<clinit>(CommPortIdentifier.java:109)
at comm.SimpleRead.main(SimpleRead.java:78)
Exception in thread "main" java.lang.UnsatisfiedLinkError: com.sun.comm.SunrayInfo.isSessionActive()Z
at com.sun.comm.SunrayInfo.isSessionActive(Native Method)
at com.sun.comm.Portmapping.registerCommPorts(Portmapping.java:155)
at com.sun.comm.Portmapping.refreshPortDatabase(Portmapping.java:100)
at javax.comm.CommPortIdentifier.<clinit>(CommPortIdentifier.java:138)
at comm.SimpleRead.main(SimpleRead.java:78)
Java Result: 1
i think i did everything about rxtx as described. could anyone help?
best regards
joshua

Problem while reading data from Serial Port

Hi All,
I am facing some problem while reading data from Serial Port.
As per the requirement I am writing the data on Serial Port and waiting for response of that data.
Notification for data availabilty is checked with method public void serialEvent(SerialPortEvent event) of javax.comm.SerialPortEventListener.
When we are writing data on the port one thread i.e. "main" thread is generated and when data availability event occures another thread "Win32SerialPort Notification thread" is generated. This creates problem for me as we can't control thread processing.
So can anybody pls explain me how to overcome this problem?
Regards,
Neha

My Problem is:-
I am simoultaneouly wrting data on port & reading data from port.
First I write data on port using outputStream.write() method. Now when target side sends me response back for the request on serial port DATA_AVAILABLE of SerialPortEventListner event occured,we are reading data from serial port.Now till the time we didn't get the response from target next command can't be written on the serial port. When we are writing data on port main thread is executed.Now my problem starts when DATA_AVAILABLE event occured.At this point another thread is created.Due to this my program writes data of next command without reading response of previous command.To solve this prob. I have used wait() & notify() methods as follows.But again due to this my pc hangs after execution of 2 commands. (PC hang in while loop in a code provided below.)
From SOPs I could figure it out that after 2 commands we are not able to write data on serial port so DATA_AVAILABLE event doesn't occure n pro. goes in wait state.
Can anybody help me to solve this issue.
Neha.
Code:
public void serialEvent(SerialPortEvent event)
          switch (event.getEventType())
               case SerialPortEvent.BI:
               case SerialPortEvent.OE:
               case SerialPortEvent.FE:
               case SerialPortEvent.PE:
               case SerialPortEvent.CD:
               case SerialPortEvent.CTS:
               case SerialPortEvent.DSR:
               case SerialPortEvent.RI:
               case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
                             break;
               case SerialPortEvent.DATA_AVAILABLE:
                    try
                         dataThread = Thread.currentThread();
                         dataThread.setPriority(10);
                         dataAvailable = true;
                                                                                byte[] tempArray=new byte[availableBytes];
                                    inputStream.read(tempArray);
                                                                   catch (IOException io)
                         SOP(io, "Error in serialEvent callback call for event DATA_AVAILABLE");
public void writetoPort(byte[] data) throws IOException
                         outputStream.write(data);
                          while(finalTimeOut >= actualTime)
                        if( ! dataAvailable)
                                actualTime = System.currentTimeMillis();
                       else
          synchronized (mainThread)
               mainThread = Thread.currentThread();
               mainThread.wait();
public void sendDatatoUser(byte[] b) throws Exception, HWCCSystemFailure
          obj.returnData(b);
          synchronized(mainThread)
               mainThread.notify();

Read data from serial port or TCP port of frontend PC

Hello Friends,
I have requirement to read data from device connected to frontend PC which will provide meter reading data.
Vendor has given me two option.
1. Device can be connected to seiral port and data transfer will be done through MODBUS RTU protocol.In that case data need to capture from serial port.
2. Device can be connected to TCP port and Socket program can be provided for data transfer. In that case SAP will act as client and communicate with TCP port.
There will be multiple workstation with individual meters connected to them.
I am aware of text file interfacing through front end tools using custom code using VB,JAVA or others.
Is there any solution availble to achieve above things using ABAP other than text file , like direct communication?
I am using ECC 6.0.

Hello,
Socket programming in not available on ABAP, but you may use RFC for the same.
Use the below links for more details
[Link 1|http://help.sap.com/printdocu/core/print46c/en/data/pdf/BCFESDE2/BCFESDE2.pdf]
[Link 2|http://forums.sdn.sap.com/thread.jspa?threadID=1820233]
Regards,
Abhishek

Reading a char array from Serial port

Need help!
Hi, I've got the following problem - I wanna read a input stream from serial port and I use at the moment the following method (reading bytewise):
public String receiveText (){
      byte ch;
      fStrBuf.delete(0,fStrBuf.length()); //clearing the buffer
try{
          do {
          ch = (byte) fPortInStream.read();
          fStrBuf.append( (char) ch);
        while ( (byte) ch != 0x03); //The end of frame byte
         }catch(IOException ioe) {};
      return fStrBuf.toString();It works pretty well, but disadvantage is that it's too slow to use it in the thread (at least I think so)
How can I change it to read all available data from the port (or simply faste). I don't need event listeners, because it's a request-responde communication.
I tried smth. like this
byte[] readBuffer = new byte[20];
            try {
                while (fPortInStream.available() > 0) {
                    int numBytes = inputStream.read(readBuffer);
                    fStrBuf.append(readBuffer);
            } catch (IOException e) {}
      return fStrBuf.toString();But it doesn't seem to work :-(

May I suggest that you use StringBuilder rather than StringBuffer. It has less overhead because it is not threadsafe. I do synchronous serial port stuff with Opto 22, and i have no listeners enabled.
Appending to the String(Builder/Buffer) directly from the byte buffer mangles it. So I use a string (ugh). With the Opto22 brain boards, i am looking for a carriage return as a term char. It either finds it or times out.
This is the best i have come up with so far:
StringBuilder response = new StringBuilder();
String data = new String();
long msTimeOut = 2000;
public void getResponse () throws IOException {
        byte[] readBuff = {0};
        int charAvail;
        response.delete(0,response.length());
        long ts = Calendar.getInstance().getTimeInMillis();
        try {
            while ( readBuff[readBuff.length-1] != '\r' ) {
                charAvail = inputStream.available();
                if ( charAvail > 0 ) {
                    readBuff = new byte[charAvail];
                    inputStream.read(readBuff);
                    response.append(new String(readBuff));
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                    response.delete(0,response.length());
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                    break;
        } catch (IOException e) { e.printStackTrace(); throw e; }
        data = response.substring(0);
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How to get data from serial port to GUI textArea

From Serial Port.....
Messages from base (always 5 bytes):
0xAA, 0, 0, 0, 0xBB - IDLE Mode
0xAA, 0, 0x80, 0x80, 0xBB - Question Mode
messages from terminal (always 6 bytes):
0xAA, a, b, c, chksum, 0xBB
where chksum = a+b+c;
a = address (0-250)
the 2 MSB's of b represenet the answer:
0 0 - A
0 1 - B
1 0 - C
1 1 - D
the 6LSB's of b and 8bits of c is the time for answer, in milliseconds.
(0-16384 milliseconds)
I have VB Code for that but I want the same thing in Java ...
Can any one help me?
Here's VB Code..
VERSION 5.00
Object = "{648A5603-2C6E-101B-82B6-000000000014}#1.1#0"; "MSCOMM32.OCX"
Begin VB.Form Form1
   BorderStyle     =   1 'Fixed Single
   Caption         =   "Aakar GUI"
   ClientHeight    =   4665
   ClientLeft      =   60
   ClientTop       =   375
   ClientWidth     =   6105
   LinkTopic       =   "Form1"
   MaxButton       =   0   'False
   MinButton       =   0   'False
   ScaleHeight     =   311
   ScaleMode       =   3 'Pixel
   ScaleWidth      =   407
   StartUpPosition =   3 'Windows Default
   Begin VB.CommandButton cmdPort
      Caption         =   "Open Port"
      Height          =   375
      Left            =   120
      TabIndex        =   4
      Top             =   600
      Width           =   1455
   End
   Begin VB.ComboBox cmbPort
      Height          =   315
      ItemData        =   "Form1.frx":0000
      Left            =   120
      List            =   "Form1.frx":0016
      Style           =   2 'Dropdown List
      TabIndex        =   3
      Top             =   120
      Width           =   2895
   End
   Begin VB.CommandButton cmdEnd
      Caption         =   "End"
      Height          =   495
      Left            =   1560
      TabIndex        =   2
      Top             =   1320
      Width           =   1215
   End
   Begin VB.CommandButton cmdStart
      Caption         =   "Start"
      Height          =   495
      Left            =   120
      TabIndex        =   1
      Top             =   1320
      Width           =   1215
   End
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      Height          =   2040
      Left            =   119
      MultiLine       =   -1 'True
      ScrollBars      =   3 'Both
      TabIndex        =   0
      Top             =   2475
      Width           =   5848
   End
   Begin VB.Timer tmrRead
      Enabled         =   0   'False
      Interval        =   1
      Left            =   2040
      Top             =   600
   End
   Begin MSCommLib.MSComm MSComm1
      Left            =   3120
      Top             =   360
      _ExtentX        =   1164
      _ExtentY        =   1164
      _Version        =   393216
      DTREnable       =   0   'False
      ParityReplace   =   45
      SThreshold      =   1
   End
   Begin VB.Label Label5
      Caption         =   "Result Data:"
      Height          =   375
      Left            =   120
      TabIndex        =   5
      Top             =   2115
      Width           =   1320
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Option Explicit
Dim PortIsOpen As Boolean
Dim Answers(4) As String
Dim RejectKeystroke As Boolean
Private Sub cmbPort_Change()
Debug.Print cmbPort.ListIndex
End Sub
Private Sub cmbPort_Validate(Cancel As Boolean)
'Cancel = True
End Sub
Private Sub cmdEnd_Click()
MSComm1.Output = "e"
txtMessage.Text = ""
End Sub
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On Error GoTo ErrorHandler
If cmbPort.ListIndex < 0 Then Exit Sub
If PortIsOpen Then
    cmbPort.Enabled = True
    MSComm1.PortOpen = False
    PortIsOpen = False
    cmdPort.Caption = "Open Port"
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    cmdEnd.Enabled = False
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    MSComm1.CommPort = cmbPort.ListIndex + 1
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    MSComm1.PortOpen = True
    PortIsOpen = True
    cmdPort.Caption = "Close Port"
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    cmdEnd.Enabled = True
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Exit Sub
ErrorHandler:
Debug.Print Err.Number
Debug.Print Err.Description
MsgBox Err.Description, vbExclamation Or vbOKOnly, "Error opening port"
cmbPort.Enabled = True
PortIsOpen = False
cmdPort.Caption = "Open Port"
cmdStart.Enabled = False
cmdEnd.Enabled = False
End Sub
Private Sub cmdStart_Click()
MSComm1.Output = "s"
txtMessage.Text = ""
End Sub
Private Sub Form_Initialize()
Dim tmp As Variant
tmp = InitCommonControls
End Sub
Private Sub Form_Load()
Answers(0) = "A"
Answers(1) = "B"
Answers(2) = "C"
Answers(3) = "D"
'MSComm1.Settings = "9600,n,8,1"
''MSComm1.Settings = "115200,n,8,1"
'MSComm1.PortOpen = True
On Error GoTo ErrorHandler1
MSComm1.CommPort = 1                    ' comm port 1
MSComm1.RThreshold = 1                  ' use 'on comm' event processing
MSComm1.Settings = "9600,n,8,1"         ' baud, parity, data bits, stop bits
MSComm1.SThreshold = 1                  ' allows us to track Tx LED
MSComm1.InputMode = comInputModeText    'comInputModeBinary ' binary mode, you can also use
                                        ' comInputModeText for text only use
PortIsOpen = False
cmbPort.ListIndex = 0
' open the port
MSComm1.PortOpen = True
cmbPort.Enabled = False
PortIsOpen = True
cmdPort.Caption = "Close Port"
cmdStart.Enabled = True
cmdEnd.Enabled = True
Exit Sub
ErrorHandler1:
Debug.Print Err.Description
PortIsOpen = False
cmbPort.Enabled = True
cmdPort.Caption = "Open Port"
cmdStart.Enabled = False
cmdEnd.Enabled = False
End Sub
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
If MSComm1.PortOpen Then MSComm1.PortOpen = False
End Sub
Private Sub lblOption_Click()
End Sub
Private Sub MSComm1_OnComm()
' Synopsis:     Handle incoming characters, 'On Comm' Event
' Description: By setting MSComm1.RThreshold = 1, this event will fire for
'               each character that arrives in the comm controls input buffer.
'               Set MSComm1.RThreshold = 0 if you want to poll the control
'               yourself, either via a TImer or within program execution loop.
'               In most cases, OnComm Event processing shown here is the prefered
'               method of processing incoming characters.
    Dim i As Long
    Dim sBuff    As String           ' buffer for holding incoming characters
    Const MTC       As String = vbCrLf ' message terminator characters (ususally vbCrLf)
    Const LenMTC    As Long = 2         ' number of terminator characters, must match MTC
    Dim iPtr        As Long             ' pointer to terminatior character
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    ' so get the Event ID & process
    Select Case MSComm1.CommEvent
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            Dim PacketLength As Integer
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            PacketStart = False
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            While (Len(sBuff) > 0)
                ch = Left(sBuff, 1)
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                If (ch = Chr(&HBB)) Then PacketStart = False
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                    PacketLength = PacketLength + 1
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                    Packet(PacketLength) = ch
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                'txtMessage.Text = txtMessage.Text + Format(Hex(Asc(ch)), " @@")
                sBuff = Right(sBuff, Len(sBuff) - 1)
            Wend
            If (PacketLength = 3) Then
                Debug.Print "Command packet recieved"
                'txtMessage.Text = txtMessage.Text + vbCrLf + "Address =" + Str(Asc(Packet(1)))
                'txtMessage.Text = txtMessage.Text + vbCrLf + "Address =" + Str(Asc(Packet(2)))
            End If
            If (PacketLength = 4) Then
                Debug.Print "Response packet recieved"
                txtMessage.Text = txtMessage.Text + "Address =" + Str(Asc(Packet(1))) + _
                    " Answer = " + Answers((Asc(Packet(2)) And &HC0) / 64) + _
                    " Time =" + Str((Asc(Packet(2)) And &H3F) * 256 + (Asc(Packet(3)))) + "mS" + vbCrLf
                'txtMessage.Text = txtMessage.Text + vbCrLf + "Address =" + Str(Asc(Packet(1)))
                'txtMessage.Text = txtMessage.Text + vbCrLf + "Option =" + Str((Asc(Packet(2)) And &HC0) / 64)
                'txtMessage.Text = txtMessage.Text + vbCrLf + "Time =" + Str((Asc(Packet(2)) And &H3F) * 256 + (Asc(Packet(3))))
            End If
            If (PacketLength <> 4 And PacketLength <> 3) Then Debug.Print "Unknown packet of length" + Str(PacketLength) + " recieved"
            txtMessage.Text = txtMessage.Text + vbCrLf
        ' An EOF charater was found in the input stream
        Case comEvEOF
            DoEvents
        ' There are SThreshold number of characters in the transmit buffer.
        Case comEvSend
            DoEvents
        ' A Break was received.
        Case comEventBreak
            DoEvents
        ' Framing Error
        Case comEventFrame
            DoEvents
        ' Data Lost.
        Case comEventOverrun
            DoEvents
        ' Receive buffer overflow.
        Case comEventRxOver
            DoEvents
        ' Parity Error.
        Case comEventRxParity
            DoEvents
        ' Transmit buffer full.
        Case comEventTxFull
        ' Unexpected error retrieving DCB]
        Case comEventDCB
            DoEvents
    End Select
End Sub
Private Sub tmrRead_Timer()
'MSComm1.Output = vbCrLf + vbCrLf
'MSComm1.Output = Chr(128)
End Sub
Private Sub txtMessage_KeyDown(KeyCode As Integer, Shift As Integer)
If Shift = 2 Or Shift = 4 Then RejectKeystroke = False Else RejectKeystroke = True
End Sub
Private Sub txtMessage_KeyPress(KeyAscii As Integer)
If RejectKeystroke Then
    KeyAscii = 0
End If
End SubThanks in advance..

I want to replicate the entire VB program as Java Program.
This has to be included in my project which i am doing in java.

How to save a datas from serial port?

How to save a datas from serial port?

Hi
I need some help about rs-232 communication. I want to make a vi witch can do this things:
-read a txt file (to simulate a serial port like when the datas are coming)
i will get 3 different data in serial port (like this: 121 213 135)
i want to save in a txt file what datas get my vi
so
-write in a txt file or draw in a diagram (or both)
so my problem is: read in serial port and save in a file and draw a diagram.
if anybody can help pls HELP ME because im a beginner in this problem.
I already do something but Im not sure that good.
Thx for all.

Java program to receive byte from serial port

hello everyone, i am recently working one a project which require communication between pic16f877 and PC. My pic continuiously measure a voltage and send the result (a byte ranging from 0 to 255) to the rs232 port. One the pc side, my java program keep reading the serial port and it works for values 0~127 and 160~255. But if the byte value is between 127 and 160, it cannot received correctly, i get something like 375,8224,or even 65532 etc(no obvious path but more likely to be 300+,700+,8000+ or 65500+). I have been trying very hard to solve this and i think the problem is due to the pc software. I am feeling so frustrated and any suggestion will be much appreciated.
p.s. : i used Bufferedreader.read() in my program
--mengyao

fumengyao wrote:
hello everyone, i am recently working one a project which require communication between pic16f877 and PC. My pic continuiously measure a voltage and send the result (a byte ranging from 0 to 255) to the rs232 port. One the pc side, my java program keep reading the serial port and it works for values 0~127 and 160~255. But if the byte value is between 127 and 160, it cannot received correctly, i get something like 375,8224,or even 65532 etc(no obvious path but more likely to be 300+,700+,8000+ or 65500+). I have been trying very hard to solve this and i think the problem is due to the pc software. I am feeling so frustrated and any suggestion will be much appreciated.
p.s. : i used Bufferedreader.read() in my program
--mengyaothis may not matter in your case - but don't use a Reader, use a Stream (BufferedInputStream maybe)

Synchronise READ from Serial card when Counter on 6025 is incremented

Hi!
System description:
I am using PXI-8423 (2-port RS-422) and PXI-6025 to measure the signal coming from 2 laser sensors mounted onto a mechanical stage with linear encoder.
The laser sensors give RS-422 output (at 1KHz) and are connected to my serial card.
The encoder gives quadrature output that I plan to connect to counters on my 6025 daqcard.
Q:
I want to read the laser data everytime the encoder gives a pulse signifying the mechanical stage has moved. How can I achieve this?
We would be taking around 1000 serial reads (from each port) per second.
Environment:
We are using PXI-1031 chassis (4-slot) with PXI-8184 controller (850 MHz celeron). OS is Win2K prof. and LabVIEW 7.1
Thanks,
Gurdas
[email protected]
Gurdas Singh
PhD. Candidate | Civil Engineering | NCSU.edu

Hi Gurdas,
We have some simple serial communication examples included in LabVIEW. Those example programs transmit any string of characters over the serial port. All you have to do is set which port you want to use, baud rate, stop bits, parity, etc. in the VI; this setting wil remain for each serial transfer while the program is running. Again, you can read/write any character string with the serial communication VI's. How the information is put into the character strings is up to you and the device you are communicating with. The serial communication is LSB before MSB.
Regards,
Salvador Santolucito
Applications Engineering
National Instruments
Attachments:
Basic_Serial_Write_and_Read.vi ‏66 KB
Advanced_Serial_Write_and_Read.vi ‏105 KB

Count time between 2 readings from serial port... help!.

Hi guys,
I am using my application to get the readings sent by microcontroller from serial port. It works perfectly. But i have the problem, the pic uses 16bits counter, and sometimes i measure frequency lower than 15hz (65535-->16bits). Thats why I thought to measure the time between each pulse that it recieved in serial port. So i could multiply the reading about the time which spend in arrive to serial port. I know if any pulse spend more than 15hz, i should add 65535 to this reading.
Then, the idea is count the time spent between each reading in serial port. SInce pics count and later send each turn.
I dont know if it is possible, and exist any easy way.. Can ayone help me?.
I would like to see any example of it, always it is possible.
Regards, Fonsi.
Attachments:
capture.GIF ‏19 KB

You're not going to be able to get even close to 1 usec resolution using the built-in time functions though I don't see any of those in your attachment. The windows clock is simply not that accurate. If you need to precisely time your serial reads you might want to look at using the timed loop. You can set the period of that to 1 msec.

Controlled reading from serial port

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