I'm a beginner in Java. I'm reading data from the serial port. I got
serialPort.setSerialPortParams(
9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
What is the meaning of 9600, DATABITS_8,STOPBITS_1 and PARITY_NONE?
When you say you "got serialPort.setSerialPortParams(....", where did you get it? If you want to understand the parameters to the method, please see the javadoc
9600, DATABITS_8,STOPBITS_1 and PARITY_NONE
9600 BAUD: Baud is synonymous with symbols or pulses per second. In this case it refers to the number of bits transferred per second.
DATABITS_8: 8-bits of data are transferred at a time. This is typical since most machines have 8-bit bytes these days.
STOPBITS_1: One trailing bit is added to mark the end of the word.
PARITY_NONE: No parity bit is included. This is an error checking feature. For even parity, a 1 is added if it would make the sum of the bits even and vice versa for odd parity. Mark and space parity are sometimes used as well. RS-232 is a low level protocol and error checking is often left to the application layer. A checksum or CRC is often included with packets of serial data for this reason. For example, Ethernet uses a 32-bit CRC for its data frames, but it never concerns an applications developer.
In RS-232 communications a start bit is always included. A universal asynchronous receiver/transmitter (UART) -- the hardware this Java library will control -- looks for this marker and then begins shifting the data bits into a buffer. So, each word in your transfer will take 10 bits: 1 start bit + 8 data bits + 1 stop bit. At 9600 BAUD, this would give you a maximum data transfer rate of 960 bytes per second even though the equivalent of 1200 bytes will be sent: 9600 bits per second divided by 10 bits per word yields 960 words per second with 8 data-bits (1 byte) per word.
This configuration you are using will commonly be abbreviated as 9600,8,N,1 for speed, data-bits, parity and stop bits in that order.