AGG Software
Ask a question  Top  Previous 


Question: Why COM port doesn't open?

Answer: Probably, some other program already uses it (COM port). This can be DOS application, for example.


Question: What to do?

Answer: Close application, using this communicative port (for DOS application close also DOS session window). Or use other communicative port. Probably, at start or some program stop was made some fatal error and COM port wasn't properly closed.


Question: Is it possible to set variable data transmit rate or transmit 9 data bits?

Answer: No, Windows operation system doesn't let such liberties.


Question: What cutoff point type to use: DB25 or DB 9?

Answer: It makes no difference, select only in program corresponding COM-port. USUALLY DB25 - COM2, DB9 - COM1


Question: Is cable connection direct or null-modem?

Answer: Everything depends on your device cutoff point. Usually it is necessary to use null-modem cable, in which signals are moved apart in this way:


Device   |   Computer


RXD <--> TXD

TXD <--> RXD

GND <--> GND


if device uses special signals DTR and others and you don't want to use hardware data transmit control, at device side connect 7 and 8 contacts of DB9 cutoff point or analogous DB25 cutoff point signals.


More hardware tips and articles you can found on our site


Question: Is data receive becomes at once after program start or data receive must be started?

Answer: Everything depends on your device type, usually in device settings is selected to echo view data to COM port. If your device doesn't support this mode, write what initialization string must be sent to read out data, and we add this possibility to the program.

Copyright © 1999-2017, AGG Software.
All rights reserved.