I am using a Duet 3 Mini 5+ currently with 3.5.0-rc.3 to control my measurement instrument prototype. I am sending commands over the serial port from Octave. It works fine to just send a lot of commands including M400 to wait for motors etc. I have not read anything back from the card. However, now I need to wait for the card to finish all commands sent, then change something external, and send more commands. What is the best way to do this synchronization? Maybe use the M111 command in the config.g to set it to give a response to every command, and have the Octave send a special code, which has a response that Octave can read and recognize?

@droftarts My M115 says FIRMWARE_NAME: RepRapFirmware for Duet 3 Mini 5+ FIRMWARE_VERSION: 3.4.0 ELECTRONICS: Duet 3 Mini5plus WiFi FIRMWARE_DATE: 2022-03-15 18:59:17
I haven't used job files, because I am building a measurement system, not a printer. I have just been sending commands over the serial port from my program on the PC. I can use macros if I have to. I will do the upgrade next week and see what happens. Thank you for your help so far, and have a nice weekend!

@Phaedrux I have a M669 K0 in my config.g, but that seems to be of no consequence. However, reading about Command queueing in the gcode dictionary suggested to put the sequence of commands into a macro. This works perfectly! Maybe there is a way to "create" a macro on the fly by sending something extra over the serial port, but that is another issue.

@droftarts Thanks, but the M400 stops the motion, so that does not work for me. I need continous motion to avoid vibrations and such.

I would like to trigger a camera while a motor is continously running.
The motor is set up to move something 360 degrees around, and the camera should be triggered at e.g every 10 degrees, as exactly as possible.
I am sending commands over the serial port. If I send 36 G1 commands in turn, the motor still runs continously.
If I send M42 commands for the trigger signal in between these G1 commands, the motor runs continously, but it seems all M42 commands are performed at once, not at the 10 degree intervals.
How can I do this?
I am using Duet Web Control 3.4.0 with the Duet 3 Mini 5+ board.