CAT via .NET SerialPort class

I sent an email to devhelp with more details:

Good morning!

I am writing a voice keyer to get familiar with CAT programming on the Flex, and I'm 99% there. My last problem is actually triggering PTT.

I have a PTT CAT port set up configured for DTR Active High, (see attached screenshot) although I can reproduce “the problem” with all the other combinations of RTS/DTR Active Low/High.

I can connect to the port using a .NET SerialPort object with no trouble.

Here is likely the basis of my confusion - I think “Active High” means setting the port to “High” or “True” will enable PTT, but it seems just the opposite. Here is some very simple .NET8 code to demonstrate:

using System.IO.Ports;

Console.WriteLine("Creating SerialPort");

using (SerialPort port = new("COM5"))

{

  port.Open();

  Console.WriteLine($"Port Open RTS={port.RtsEnable} DTR={port.DtrEnable}");

  // Flex CAT set to DTR Active HI

  // So this should key the radio BUT IT DOES NOT!

  port.DtrEnable = true;

  Console.WriteLine($"PTT ON RTS={port.RtsEnable} DTR={port.DtrEnable}");

  Console.ReadKey();

  // And this should unkey it BUT THE RADIO GOES INTO TRANSMIT!

  port.DtrEnable = false;

  Console.WriteLine($"PTT OFF RTS={port.RtsEnable} DTR={port.DtrEnable}");

  Console.ReadKey();

  port.Close();

}

The output is:

Creating SerialPort

Port Open RTS=False DTR=False

PTT ON RTS=False DTR=True      ←- RADIO IS NOT KEYED

PTT OFF RTS=False DTR=False    ←-- RADIO IS KEYED!!

Note that even after the program closes the radio stays keyed and I have to shut down SmartSDR to get it to unkey.

So it seems that my understanding of “Active High” is backwards - a port set to “Active High” should be set to LOW/False to key the radio and vice-versa.

Does this make any sense?

Thank you, and 73!

-Brian n8wrl

Hi Len!

Switching on/off of RTS affects PTT but not the way I would expect.

When I set up PTT CAT with the RTS line and "Active High" setting RTS to FALSE turns on PTT.

It's backwards - Active High needs FALSE while Active Low needs TRUE.

I gotta believe it's just my misunderstanding. So much software is already in use. I must be doing something wrong.

73

-Brian n8wrl