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| FAQs |
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Question: Why doesn't the COM port open?
Answer: Probably, some other program already uses it (COM port). This can be some DOS application, for example.
Question: What should I do?
Answer: Close the application that uses this serial port (close also the DOS session window for a DOS application). Or use another serial port. Probably, when some program was started or closed, there was some fatal error and the COM port was not properly closed.
Question: Is it possible to set a variable data transmission rate or transmit 9 data bits?
Answer: No, the Windows operating system does not allow it.
Question: What serial connector should I use: DB25 or DB9?
Answer: It makes no difference, only select the corresponding COM port in the program. USUALLY, DB25 - COM2 and DB9 - COM1
Question: Is the cable connection direct or null-modem?
Answer:Everything depends on the serial interface of your device. Usually, you should use a null-modem cable where signals move apart in the following way:
Device | Computer
_____________
RXD <--> TXD
TXD <--> RXD
GND <--> GND
If your device uses special signals (DTR and others) and you do not want to use hardware data transmission control, connect the 7th and 8th contacts of the DB9 connector or similar DB25 signals.
You can find more hardware tips and articles at our site http://www.fogsoft.com.
Question: Is data received right after the program is started or must it be initiated somehow?
Answer: Everything depends on the type of your device. Usually, it is selected to echo data to the COM port in the device settings. If your device does not support this mode, write what initialization string must be sent to read data and we will add it to the program.
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