fldigi tests to see the connected device is performing as a Winkeyer using the Immediate Admin command for echo test:
Immediate Admin Commands
nn is a value from 0 to 8
After power-up the host interface is closed, serial status, echo, or pot change data will be not be sent to the
host. The only commands WK2 will accept are Admin commands. Admin commands are received,
processed and any return status or data will be sent back immediately. Admin commands calibrate the
interface, reset WK, obtain debug information and open the interface. With the exception of the Amin:Close
command, all Admin commands should only be issued while the host interface is closed. Following are
descriptions of the Admin commands:
0: Calibrate This is an historical command preserved for WK1 compatibility. It is no longer required for
the more accurate PIC the WK2 is implemented on. You can issue the command and it
will not cause ill effects, but it is not processed by WK2. The command syntax is:
<00><00> pause 100 mSec <FF>
1: Reset Resets the Winkeyer2 processor to the power up state. Do not send this as part of the
initialization sequence. Only send this if you want to do a cold reboot of WK2.
2: Host Open Upon power-up, Winkeyer2 initializes with the host mode turned off. To enable host mode,
the PC host must issue the admin:open command. Upon open, Winkeyer2 will respond by
sending the revision code back to the host. The host must wait for this return code before
any other commands or data can be sent to Winkeyer2. Upon open, WK1 mode is set.
3: Host Close Use this command to turn off the host interface. Winkeyer2 will return to standby mode
after this command is issued. Standby settings will be restored.
4: Echo Test Used to test the serial interface. The next character sent to Winkeyer2 after this command
will be echoed back to the host.
After establishing the serial connection the serial data stream x00 x04 'U' is sent. Fldigi then waits up to 5 seconds for the echo response 'U'.
The K3NG sketch is not responding to the echo test, so fldigi code declares it as not responsive.
You might want to look over the K3NG sketch code to see if it designed to perform the echo test.
73, David, W1HKJ