Here is a piece of software as DC42 suggested. Thanks! An Arduino Nano is connected to the Panel-Due serial interface. Hidden in a box it works to move the tool head of my CNC-Mill controlled by Duet2 Ethernet.
Arduino is 5 V, Duet2 interface is 3.3V. Serial connection is done via 3,3 V to 5 V level shifter!
This line is added to my config.g : M575 P1 B57600 S0 to set communication without CRC check.
Push button for directions, continuous move(Fortl.), homing and a switch to start jog mode in general are connected to the input pins of Arduino.
Pushing a "direction button" moves the head a step with the configured distance. Pressing the "Fortl.(Continuous)" button simultaneous with a "direction button" moves the tool head continuously as long as both buttons are down.
A "Home" button does the expected job.
Values for distance, feed rate and timers can be modified to match software to your machine.
A limitation at my machine: Continuous moves are singel steps fired continuously by Arduino. First steps fired are slowed down at the end a little bit until enough commands are buffered. Movement sounds a bit strange.
I transferred this code is to Arduino via "B4R" form Anywhere Software. Download of B4R is free.
B4R needs extension ".B4R". Please remove extension ".TXT" from filname.