LinuxCNC M68 Analog Output, Immediate

M68 is a LinuxCNC G-code that sets an analog output immediately. It uses an E word for the output number and a Q word for the value, with Q set to 0 turning the output off. Because the output is applied immediately rather than queued with motion, it can break blending.

Source checked7/7 values · 2026-10-26

Specification

1 source

Language	gcode
Code	M68
Group	Analog Output Control
Syntax	M68 E- Q-
Dialect	LinuxCNC

Parameters

Name	Description
E	Output number ranging from 0 to 3; adjustable from the motmod argument num aio.
Q	Value to set; set to 0 to turn the output off.

Study notes

The document states that M68 functions the same as M64-M65.
M68 output happens immediately as received by the motion controller and is not synchronized with movement.
Immediate M68 output changes can break blending.
M68 will not function unless the appropriate motion.analog-out-nn pins are connected in the HAL file to outputs.

Safety

Output number E ranges from 0 to 3, adjustable with the motmod argument num_aio.