Advertisement
(3) USB interface itself has relatively strong power supply ability. Therefore,
USBRS-485/422 converter has no need of external power supply (i.e. it is free from
power shortage). In addition, USB has such advantages as hot plug, convenient
connection, connecting with multiple devices, etc.
How does USB485× converter realize the application software communication with
RS-485/422 device? It is necessary for users to understand the realization process. The detailed
principle is described as follows:
After the driver program of USB485× is installed, a virtual serial COM port will be formed
automatically in your computer system. For example, your computer has both COM1 and COM2
serial ports originally, and after USB485× driver program is installed, a virtual COM3 port will be
formed automatically (generally speaking, it is like this; concrete COM port number is allocated
automatically by virtual driver program). If your computer has no RS-232 interface (e.g. relatively
new notebook computer), a virtual COM1 port will be formed automatically after the driver
program is installed.
The virtual COM port from USB485× driver program and the original COM port from
computer are the same for application software. As long as your application software can map (or
select) to the virtual COM port, the communication with RS-485/422 device will be realized, i.e.
the conversion process from virtual COM port driver program to calling USB driver program, and
then to RS-485/422 is completely transparent for users, and users need not pay attention to
realization details of the process and nothing remains but to consider the serial port
communication.
The following diagram may help you understand the conversion process:
Advertisement
