rs232 rts dtr high after close

[Christine T]

Hi,

I'm connecting a pc to a tt20, an instrument which measures thickness, through a serial interface.

On my laptop, the program works fine. On a laptop (chinese origin), tt20 reacts in a random way.

I must say, once it starts, it usualy keeps on going.

It is clearly the tt20 that doens't recieive the commands in a proper way, because the command i am sending doesn't appear on the tt20-display.

The manufacturer of tt20 recommended to put the DTR line high and de RTS line low after writing to the serial port.

Today, we put a device (don't know the name of it) between the serial port of the pc and the tt20, that shows wich lines are high and which lines are low.

During the communication, the lines seem to react the same. But when i close the serial connection, all lines connected to my pc are low, which is most common, i presume. If the lines are connected to the other laptop, they remain high.

So i think the problem lies within initialisation of the serial port.

I tried all possible combinations of the dtr and rts setting, after i open the serial communication. No succes

Is there another initialisation involved ?

Many thanks in advance

Kind Regards

Christine

[RavensFan]

A shot in the dark.

How do the settings between the two computers compare for the serial ports in Windows device manager?  Is it possible the Flow control settings are different at the Windows device manager level, such as one being set for hardware control and the other not?

[Christine T]

Hi,

As far as i can see, all settings in the windows device manager are the same

Thanks

Christine

[Ben]

Check to make sure you have a good ground reference between the laptop and the device.

I have seen ground issues with some laptops that will prevent code that runs fine on one machine to run on others.

Next:

Not all serial ports support hardware flow control. Check on that next.

If you have a good ground and the PC support hardware handshaking, then the hardware handshaking can be manipulated via property nodes, but first, verify the points above.

Ben