Big delay between write and read operation using Java Serial communication jssc library

Question

I'm developing a Java application which uses jssc library for serial port communication with external device. I need to send a command and then immediatelly read the answer back. The problem which I`m facing is that without 200 ms delay between write and read command the answer is empty. I have developed similar functionality using python and in python it works perfectly, but in Java due to 200 ms delay the communication is very slow. I would like to ask if is it any possibility to make it faster? I have been trying, closing ang opening port between operation, purge port but without any success. Thank you in advance for your help. Bellow you can find my code

serialPort = new SerialPort(getPortName());

        if (false == serialPort.isOpened()) {
            try {

                logger.debug("Opening serial port: " + getPortName());
                // Open port
                serialPort.openPort();
                // We expose the settings. You can also use this line - serialPort.setParams(9600, 8, 1, 0);
                serialPort.setParams(SerialPort.BAUDRATE_115200, SerialPort.DATABITS_8, SerialPort.STOPBITS_1,
                        SerialPort.PARITY_NONE);
            } catch (SerialPortException ex) {
                logger.error("Exceptiion during opening port: " + ex);
            }
        }
serialPort.writeBytes(cmd);
            logger.debug("command sended=" + javax.xml.bind.DatatypeConverter.printHexBinary(cmd));
            // delay added because java didn`t read data at once
            Thread.sleep(200);

            answer = serialPort.readBytes();

Answer 1

I think JSSC is based on Javax comm api javax.comm, this API has a delay of 200ms while sending a command and then reading the reply... i think thats why you don't get any response when trying to read before the 200ms...

This is my output times using javax.comms, I'm trying to find a solution for this delay, I'm using serial comms to communicate with an ESP8266

2016-11-08 12:32:31.155[INFO]Starting the receiver 2016-11-08 12:32:31.355[INFO]Receives first char 200ms after..

will try a few things and post if I got a solution... also posting this here in case someone finds a solution.

-------UDATE-------------(sorry for all the comments im new on StackOverflow)

In javax comms API there is a property to set the time that the reader will wait for data, by default is set to 200 ms (Too much i guess) you can set it to wichever value you want, but take in mind that you could read after the data has arrived and get a -1 as response byte:

            port = (javax.comm.SerialPort) portId.open( String.valueOf( this ), (int) timeout );
            port.setSerialPortParams( freq, dataBits, stopBits, parity );
            port.enableReceiveTimeout( 0 );

with this and a little reprograming of my code i got responses in less than 3 ms, I guess something similar is happening in JSSC.

2016-11-08 01:43:32.875[DEBUG]Starting the receiver 2016-11-08 01:43:32.878[DEBUG]Receives first char 3ms after