There are several Delphi components already out there for communicating with serial ports. The best one that I use is Async Professional by TurboPower. There are also several free components for mainly writing to a serial port. Good luck.
I have developed a MS Visual Basic 6.0 program to communicate with inverters through the PC serial ports. I have used the MS Comm Control to develop the serial communication and it is very easy: you have the SETTINGS property to set the communication format, the PORTOPEN property to open/close the port, the OUTPUT property to send out telegrams, the INPUT property to read incoming telegrams, the ONCOMM event to understand when characters have arrived or communication errors have occured (this event may be customized). And all is working correctly also under WINNT. Unfortunately I do not know Delphi programming but I think that Active-X technology may be used as well.
