ModbusSerialTransport.getInterFrameDelay returns wrong values if the baudrate is below 19200

[pierantoniomerlino]

The getInterFrameDelay in ModbusSerialTransport returns milliseconds values instead of microseconds if the baudrate is below 19200. The following method:

/**
 * In microseconds
 *
 * @return Delay between frames
 */
int getInterFrameDelay() {
    if (commPort.getBaudRate() > 19200) {
        return 1750;
    }
    else {
        return Math.max(getCharInterval(Modbus.INTER_MESSAGE_GAP), Modbus.MINIMUM_TRANSMIT_DELAY);
    }
}

calls the getCharInterval method when the baudrate is less than 19200. However, the getCharInterval, as shown below, returns a millisecond value:

/**
 * Calculates an interval based on a set number of characters.
 * Used for message timings.
 *
 * @param chars Number of characters
 * @return char interval in milliseconds
 */
int getCharInterval(double chars) {
    return (int) (getCharIntervalMicro(chars) / 1000);
}

So, I got 2 instead of 2000 for 19200. Indeed, I suppose that replacing the getCharInterval with getCharIntervalMicro will fix the issue. Moreover, the getCharIntervalMicro computes the interval based on the packet length. This includes also the number of stop bits, but the SerialPort.getNumStopBits method returns one of these:

// Number of Stop Bits
static final public int ONE_STOP_BIT = 1;
static final public int ONE_POINT_FIVE_STOP_BITS = 2;
static final public int TWO_STOP_BITS = 3;

Is it correct that the two-stop-bits correspond to 3 bits?

Expected Behavior

The getInterFrameDelay has to return milliseconds values instead of microseconds to get the correct interframe delay.

Actual Behavior

With 19200 baudrate the interframe delay is rounded to 0.

Specifications

• Version: 2.5.5 (but it seems to be present also in the development branch)
• Platform:
• Subsystem: