Unable to reset ixoff flag

[ilpk]

I have been having trouble communicating with a device that uses no flow control, and I think that the problem is due to the way jSerialComm handles the XON/XOFF flags (Linux, jSerialComm 2.6.2). The ixoff flag is occasionally switched on on my computer before the Java program starts up. In SerialPort_Posix.c line 274, Java_com_fazecast_jSerialComm_SerialPort_openPortNative, the serial port is opened to a sane default: options.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON); I suspect that IXOFF should also be in the list.

The other half of the problem is in Java_com_fazecast_jSerialComm_SerialPort_configPort, line 350, where we see: options.c_iflag |= (XonXoffInEnabled | XonXoffOutEnabled); This allows us to enable these flags, but not to disable them, since setting the values to 0 leaves the flags unchanged.

Is this a program bug, or am I missing something?

Best wishes,

Paul

[hedgecrw]

This does appear to be a bug...good catch! Please test the following pre-release version and see if it resolves your issue:

https://drive.google.com/file/d/11jqbkGWJA26GW_pS5fcq02LHFWkWZot4/view?usp=sharing

[ilpk]

Unfortunately it appears to make no difference. I used the small test program below:

import com.fazecast.jSerialComm.SerialPort;

public class TestSerial { public static void main(String[] args) { SerialPort serialPort = null;

for (SerialPort device : SerialPort.getCommPorts()) {
  if (device.getSystemPortName().toLowerCase().endsWith("ttyusb0")) {
    serialPort = device;
    break;
  }
}

serialPort.openPort(100);

System.out.println("Serial port open:" + serialPort.getSystemPortName());
try {Thread.sleep(10000);} catch (Exception e) {}

serialPort.setBaudRate(9600);
serialPort.setNumDataBits(8);
serialPort.setNumStopBits(1);
serialPort.setParity(SerialPort.NO_PARITY);
serialPort.setFlowControl(SerialPort.FLOW_CONTROL_DISABLED);

System.out.println("Serial port no flow control");
try {Thread.sleep(10000);} catch (Exception e) {}

serialPort.setBaudRate(9600);
serialPort.setNumDataBits(8);
serialPort.setNumStopBits(1);
serialPort.setParity(SerialPort.NO_PARITY);
serialPort.setFlowControl(SerialPort.FLOW_CONTROL_XONXOFF_IN_ENABLED | SerialPort.FLOW_CONTROL_XONXOFF_OUT_ENABLED);

System.out.println("Serial port XON/XOFF");
try {Thread.sleep(10000);} catch (Exception e) {}

serialPort.setBaudRate(9600);
serialPort.setNumDataBits(8);
serialPort.setNumStopBits(1);
serialPort.setParity(SerialPort.NO_PARITY);
serialPort.setFlowControl(SerialPort.FLOW_CONTROL_DISABLED);

System.out.println("Serial port no flow control");
try {Thread.sleep(10000);} catch (Exception e) {}

} }

Running an 'stty -F /dev/ttyUSB0' from the command line during each of the 10 second pauses gives the following result:

After open ...

stty -F /dev/ttyUSB0

speed 9600 baud; line = 0; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ; eol2 = ; swtch = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 0; time = 0; -icrnl -imaxbel -opost -isig -icanon -iexten -echo

After no flow control

stty -F /dev/ttyUSB0

speed 9600 baud; line = 0; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ; eol2 = ; swtch = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 0; time = 0; -icrnl -imaxbel -opost -isig -icanon -iexten -echo

After xon/xoff

stty -F /dev/ttyUSB0

speed 9600 baud; line = 0; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ; eol2 = ; swtch = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 0; time = 0; -icrnl ixoff -imaxbel -opost -isig -icanon -iexten -echo

After no flow control

stty -F /dev/ttyUSB0

speed 9600 baud; line = 0; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ; eol2 = ; swtch = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 0; time = 0; -icrnl ixoff -imaxbel -opost -isig -icanon -iexten -echo

The xon/xoff flags appear to never get cleared. If I set them by hand before starting the test program (e.g. stty -F /dev/ttyUSB0 ixoff) then the flags do not get cleared when the serial port is opened, and also not when the flow control is set to none.

I am using the jSerialComm-2.8.0.jar you sent, with an md5sum of 1651803ff5409105740ed31523a9b310

[hedgecrw]

Please test the attached library version and see if it works any better for you. There have been a ton of recent changes that have not made it into an actual release yet. Thanks!

https://drive.google.com/file/d/1hH2hXCEj39WUN1iz3F1TzLrpNvUro_aL/view?usp=sharing

[hedgecrw]

Please use this version for testing: https://drive.google.com/file/d/1QzWPJg5MU_2YrnsB1MsOWeTbjYD84D2h/view?usp=sharing

[ilpk]

Hi Will,

I have tested again with jSerialComm-2.8.0-beta.jar and everything seems to work. Upon initialization the xon flag is cleared, and the program can set it on and off. Thank you for your support.

Best wishes,

Paul

[hedgecrw]

Solved in release of jSerialComm v2.8.0.