SuperLongBoard(-ext) + PwnCNC Spindle System
Installation & Troubleshooting Guide (Modbus)
Thank you for choosing PwnCNC.
This guide covers proper installation and troubleshooting when using a PwnCNC spindle with the SuperLongBoard(-ext) controller over Modbus communication.
The SuperLongBoard uses grblHAL + Modbus, which requires correct two-way communication between the controller and the VFD. Unlike simple PWM systems, Modbus requires configuration on both sides.
BEFORE YOU TROUBLESHOOT
Step 1 – Confirm Hardware First
Put the VFD into manual mode using the VFD's keypad.
• Start the spindle from the VFD keypad
• Increase and decrease RPM
• Confirm smooth operation
If the spindle runs correctly in manual mode:
• The spindle is functional
• The VFD is functional
• Motor wiring is correct
• Power supply is correct
At this point, any Alarm 14 or startup failure is a Modbus communication configuration issue inside gSender / grblHAL, not a hardware failure.
Do NOT change motor parameters if manual mode works.
WIRING
Modbus requires two communication wires.
Controller Wiring (SuperLongBoard-ext)
Use the internal Phoenix connector.
Wire as follows:
• SG+
• SG-
Ensure polarity matches the VFD.
Loose or reversed wiring will prevent communication.
VFD Wiring – Spindle Kit
If using the bare VFD:
Wire into the Phoenix terminal inside the VFD:
• Black → SG-
• Red → SG+
VFD Wiring – Spindle System
If using our enclosed Spindle System:
Plug the GX12 2-pin connector into the port labeled:
Modbus
Ensure the Manual Override Switch is set to “O” (down position).
VFD PROGRAMMING (Modbus Parameters)
Your VFD ships pre-programmed. Verify only if troubleshooting.
Navigate parameters using the VFD keypad.
The following values must match exactly:
P0.0.03 = 2
P0.0.04 = 9
P0.0.11 = 6
P2.0.02 = 21
P4.1.00 = 4
P4.1.01 = 3
If these differ, correct them before continuing.
Do NOT modify unrelated motor parameters.
CONFIGURING gSender (grblHAL Modbus)
Modbus requires correct firmware configuration.
We strongly recommend exporting your current settings before making changes:
gSender → Config → Export
This will produce a .json file with your settings inside.
Known Working grblHAL Settings
The following values must match exactly:
$16 = 0
$30 = 24000
$31 = 6000
$340 = 0
$374 = 19200
$375 = 50
$392 = 6
$395 = MODVFD
$462 = 40960
$463 = 40961
$464 = 36864
$465 = 1
$466 = 2
$467 = 6
$468 = 25
$476 = 1
If $476 is unavailable, check neighboring parameter $478 for spindle address.
Baud rate must match between VFD and grblHAL.
If any value differs, correct it and reboot the controller.
ALARM 14 – WHAT IT MEANS
Alarm 14 in grblHAL is: “Spindle at Speed Timeout”
This means:
The controller did not receive confirmation from the VFD that the spindle reached commanded speed within the allowed time.
Alarm 14 does NOT automatically mean:
• The spindle is defective
• The VFD is defective
• The motor is wired incorrectly
If manual mode works, this alarm is a Modbus communication configuration issue.
Common causes:
• Baud rate mismatch
• Slave ID mismatch
• Incorrect register mapping
• Spindle-at-speed confirmation not enabled
• Timeout shorter than acceleration time
FAST ISOLATION TEST
To verify Modbus communication:
-
Open gSender Console
-
Type: M3 S12000
-
Press Enter
Observe:
• Does spindle start?
• Does Alarm 14 trigger immediately?
• Does it start but stop after timeout?
If it starts and runs:
Hardware and Modbus are functioning. Check your post processor.
If Alarm 14 appears:
Configuration mismatch exists in grblHAL settings.
IMPORTING KNOWN WORKING SETTINGS
If configuration drift is suspected:
-
Export your current firmware settings
-
Import the PwnCNC provided settings JSON (attached to the bottom of this article)
-
Reboot controller
This resolves most cases immediately.
gSender VERSION NOTE
Some versions of gSender have demonstrated inconsistent Modbus behavior.
If experiencing persistent Alarm 14 issues:
• Install gSender version 1.5.4 or 1.4.2
• Configure spindle
• Once functioning, upgrading often retains working configuration
gSender releases can be found here: https://github.com/Sienci-Labs/gsender/releases
WHEN TO CONTACT SUPPORT
If you still experience issues, email support with:
• Screenshot of gSender Spindle Settings page
• Screenshot of full $$ output
• Photo of Modbus wiring
• Confirmation that spindle runs in manual mode
Incomplete requests may delay troubleshooting.
SUMMARY
If spindle runs in manual mode, hardware is confirmed working.
Alarm 14 indicates a communication timeout between grblHAL and the VFD.
The solution is configuration alignment, not VFD/motor replacement.
