# Gsender turning on Switch when spindle activates **URL:** \ **Category:** ❓ Question\ **Created:** [January 18, 2026, 2:21am UTC](https://forum.sienci.com/t/gsender-turning-on-switch-when-spindle-activates/25461 "2026-01-18T02:21:07Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![KGN](https://forum.sienci.com/letter_avatar_proxy/v4/letter/k/c77e96/32.png) [@KGN](https://forum.sienci.com/u/KGN)\ **Post date:** [January 19, 2026, 3:39pm UTC](https://forum.sienci.com/t/gsender-turning-on-switch-when-spindle-activates/25461/2 "2026-01-19T15:39:03Z")
So you didn’t include any relevant information about your hardware setup here but I’m going to use the assumption that you are using some sort of grblHAL device. It’s possible that you have an event linked in your firmware configuration to a specific AUX pin for the spindle on trigger (M3/M4) **If you’re using SienciHAL (SLB or SLB-EXT without having flashed a more recent version of grblHAL):** You need to check that whatever port your ATC switch release is set to does not trigger on M3/M4. This is configured by changing $456-$459, which each directly map a trigger to a specific aux (Aux 0, 1, 2, 3 in order) directly. ![gSender_tefxu0ixKw](https://forum.sienci.com/uploads/default/original/2X/c/c3eac4c2edc06e4a99db6fca5b11c571f282709e.png) You’ll probably have to set the output to M64-65 only option to act as “disabled” for SienciHAL. **If you’re using a more modern version of the grblHAL firmware** You’d need to verify your Event Trigger Source Selection ($750-759) to see if any are set to activate on spindle enable (event 1). > **[$750 - $759 – Event Trigger Source Selection (Eventout Plugin)​ - Complete...](https://petervanderwalt.github.io/grblhal_docs/Reference/complete-settings-reference/#750---759--event-trigger-source-selection-eventout-plugin)** > > This page is a comprehensive reference for all known grblHAL settings. It is designed to be a single source of truth for configuration. Use the table of contents on the right to navigate to a specific section, or use your browser's search function... At that point you’d need to update the related port assignment to either activate/stop activating the aux pin. Event always directly correlate to the port assignment (So $750 triggers $760, $751 triggers $761 etc). > **[$760 - $769 – Event I/O Port Assignment (Eventout Plugin)​ - Complete Settings...](https://petervanderwalt.github.io/grblhal_docs/Reference/complete-settings-reference/#760---769--event-io-port-assignment-eventout-plugin)** > > This page is a comprehensive reference for all known grblHAL settings. It is designed to be a single source of truth for configuration. Use the table of contents on the right to navigate to a specific section, or use your browser's search function... --- _[View the full topic](https://forum.sienci.com/t/gsender-turning-on-switch-when-spindle-activates/25461)._