ActiveXperts Serial Port Component KB - Using Serial Port Component
'Using Serial Port Component' Knowledge Base Articles
| Q3100010 | What is flow control? |
| In many scenario's, it is necessary for the transmitting device to know whether the receiving device is ready to receive information. You might, for example, be sending data to a printer, and the speed of communication may be faster than the speed of the printer. The printer will need to be able t ... | |
| Q3100015 | What is the difference between hardware flow control and software flow control? |
| Both are used for handshaking (see also FAQ item 3100010). With Hardware Flow Control, the receiving device sends a positive voltage along a dedicated handshaking circuit as long as it is ready to receive. When the transmitting computer receives a negative voltage, it knows to stop sending da ... | |
| Q3100020 | Do I need hardware flow control? |
| This depends on the the DCE (Data Carrier Equipment), the device to which you are connected. If this device requires hardware flow control, you'll need it too. In most cases, hardware flow control is required that's why it is enabled by default. For more details, please read FAQ item 3100010 ... | |
| Q3100025 | Do I need software flow control? |
| Software flow control is only used for data transfer. By default, flow control is switched off. Devices like modems (sending/receiving to eachother) requiore software flow as soon as data transfer begins. For more details, please read FAQ item 3100010 and FAQ item Q3100015. ... | |
| Q3100030 | Can I change the baud rate for a port when it is already opened? |
| Yes you can. Set the BaudRate property and call the UpdateCom function to apply the property change. ... | |
| Q3100035 | What does the ComTimeout property mean? |
| The ComTimeout property is the timeout in milliseconds before functions ReadString, ReadBytes and ReadByte return. ... | |
| Q3100040 | Can I change flow control for an open port? |
| You can't change your hardware flow while a port is opened you must specify the hardware flow control before you Open the port. Software flow control can be changed while a port is opened. First change the SoftwareFlowControl property, and the call the UpdateCom function to apply the proper ... | |
| Q3100045 | Are USB devices supported? |
| Only when the USB device provides a serial port driver. For instance, most modem manufacturers provide serial port drivers for their modems, so that the modem can be accessed through a virtual COM port. These modems can be used by ActiveXperts Serial Port Component. ... | |
| Q3100050 | When I open a port, I get the following error: 30102 ("Unable to perform operation because the device does not exist"). What does it mean? |
| This means that the COM port does not exist. Error 30102 does NOT mean that the port is already in use. If the port is in use, error 30103 will be reported ("Unable to perform operation because the device is already opened") instead. ... | |
| Q3100055 | When I open a port, I get the following error: 30103 ("Unable to perform operation because the device is already opened"). What does it mean? |
| This means that the port you are attempting to open is already in use by another application. Check if there's another application that is already using the COM port. In some situations, you may want to benefit from a thing called 'port sharing', where one port can be shared by multiple a ... | |
| Q3100060 | When I open a port, I get the following error: 30201 ("Cannot find specified devicename"). What does it mean? |
| This means that the Windows Telephony Device you are using, is NOT defined on the computer. You may have made a typing mistake. Error 30201 does NOT mean that the port is already in use (you would get error 30202). ... | |
| Q3100065 | When I open a port, I get the following error: 30202 ("Cannot open specified device"). What does it mean? |
| The means implies that the Windows Telephony device is valid, but that the associated COM port is either already in use, or does not exist. The error does NOT mean that the Windows Telephony device is invalid (that would reported as error 30201) it neither means that the Windows Telephony dev ... | |
| Q3100070 | When I open a port, I get the following error: 30203 ("TAPI Device Manager failed to respond"). What does it mean? |
| The Windows Telephony device name is valid,. There can be two reasons for this error: The Windows Telephony device is already in use by another application The port speed is wrong Windows is able to open the port, but is not able to initialize the device properly because of the wrong spee ... | |
| Q3100080 | I'm using a GSM modem (WaveCom Fastrack). I get the following error: 30351 ("Unexpected response from modem"). In the log file, I see some undisplayable characters beinig received from the modem. What could be the problem? |
| Most probably, the baud rate causes the problem: COM port and modem are not sending/receving at the same speed. We stronly recommend to change the baud rate to the same speed configured for the modem. ... | |
| Q3100100 | I'm transmitting through a pretty slow device. What I need is a small delay between the characters transmitted when using your WriteString function. How can I achieve this? |
| It is easy to achieve, using the InterCharDelay property. This propery indicates the delay (in milliseconds) used by the WriteString and WriteBytes between each byte transmitted. Please note there's also another property that can be used for slower devices: PreCommandDelay. It specifies a de ... | |
| Q3100110 | Can I play a sound file on my modem using ActiveXperts Serial Port Component? |
| Yes, as long as your modem supports a voice command set. It is easy to find out if your modem supports voice or not: issue the 'AT+FCLASS=?'. A modem supporting voice will respond with a list of numbers that includes the number 8. To enter voice mode, issue the following command: 'AT+FCLASS ... | |
| Q3100120 | With ActiveXperts Serial Port Component, we sometimes receive incomplete strings. What is wrong? |
| Most probably it takes to long to read strings from the device. For instance, there's a time-out before the end-of-line character is received. To fix this problem, try to increase the ComTimeout value. ... | |
| Q3100130 | Does ActiveXperts Serial Port Component trigger an event when new data has arrived? |
| No, the component does not trigger events. All received data is buffered in memory. You need to poll for new data using a timer, or use a separate thread for receiving your data. ... | |
| Q3100140 | I need to sense the DSR signal change. How can I do this? |
| ActiveXperts Serial Port Component is not event driven. You need to call the QueryDSR function to check the state of the DSR signal. If you need to check the state continuously, you need to call this function regularly, probably in a separate thread. To monitor CTS (Clear-To-Send), use the ... |
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