# Firmware Upgrade and PWNCNC Spindle **URL:** \ **Category:** ❓ Question\ **Created:** [June 16, 2026, 7:55pm UTC](https://forum.sienci.com/t/firmware-upgrade-and-pwncnc-spindle/26588 "2026-06-16T19:55:06Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![rswood1](https://forum.sienci.com/letter_avatar_proxy/v4/letter/r/5fc32e/32.png) [@rswood1](https://forum.sienci.com/u/rswood1)\ **Post date:** [June 16, 2026, 7:55pm UTC](https://forum.sienci.com/t/firmware-upgrade-and-pwncnc-spindle/26588/1 "2026-06-16T19:55:07Z")
I am about to update my SLB EXT on my Altmill I am using the PWNCNC 1.5 spindle which I have checked off as the MODVFD for spinsle 1. I just want to make sure I am downloading the correct version of the latest fiemware. There are two choices. 1 - SLB EXT (AltMill): - Version **20260525** - Newest, main version of grblHAL - Requires gSender 1.6.2 or newer - Unplug the VFD for firmware flashing 2 - SLB EXT (AltMill) **ONLY** for users with Huanyang or generic ‘MODVFD’ spindle setups: - Newest, main version of grblHAL - Requires gSender 1.6.0 or newer - Specific firmware require for use with Huanyang ‘V1’ or ‘P2A’ VFDs or generic spindles using ‘MODVFD’. - Read more about the use of the ‘MODVFD’ spindle profile for generic VFDs I’m assuming number 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:** [June 16, 2026, 8:46pm UTC](https://forum.sienci.com/t/firmware-upgrade-and-pwncnc-spindle/26588/2 "2026-06-16T20:46:13Z")
This is not really a gSender issue, but 20260525 main\_grblHAL (option 1) has all spindles compiled in, including MODVFD thanks to some web builder updates - we’re no longer limited to only having 4 spindle options per build. ![Screenshot 2026-06-16 at 4.28.53 PM](https://forum.sienci.com/uploads/default/original/2X/a/a4b3a26345f11cd4910ec74e505118cf64c3d8d4.png) You’d just need to enable it as a selectable spindle in Config since only PWM is enabled by default. The second option is no longer necessary and I’ve asked support to get it removed. The first option should work for you. ---
**Author:** ![rswood1](https://forum.sienci.com/letter_avatar_proxy/v4/letter/r/5fc32e/32.png) [@rswood1](https://forum.sienci.com/u/rswood1)\ **Post date:** [June 16, 2026, 9:26pm UTC](https://forum.sienci.com/t/firmware-upgrade-and-pwncnc-spindle/26588/3 "2026-06-16T21:26:33Z")
Thanks for the quick response. ---
**Author:** ![KGN](https://forum.sienci.com/letter_avatar_proxy/v4/letter/k/c77e96/32.png) [@KGN](https://forum.sienci.com/u/KGN)\ **Post date:** [June 17, 2026, 11:41am UTC](https://forum.sienci.com/t/firmware-upgrade-and-pwncnc-spindle/26588/4 "2026-06-17T11:41:02Z")