Folinn / Fuling BD612 Series VFD — grblHAL MODVFD Setup Guide

Hardware: Zhejiang New Folinn Electric Co. BD612 Series (also sold as BD600 — unit splashes BD600 on boot) Spindle: 4.5kW, 800Hz, 24000rpm, 220V 3-phase, 20A rated Controller: Expatria Technologies FlexiHAL (STM32F446, grblHAL firmware) Plugin: MODVFD v0.05 (grblHAL Plugins_spindle) Communication: Modbus RTU over RS485 Last verified: 2026-05-17

Background

The BD612 is an engraving-machine-specific variant of the BD600 series. The unit's keypad displays BD600 on power-up splash. Parameters and register addresses from the full BD600 manual apply, with exceptions noted below.

Register addresses were determined empirically using mbpoll and cross-referenced against a LinuxCNC vfdmod configuration shared by user H2B on the LinuxCNC forum (thread: "Vfdmod — An easy VFD control over MODBUS RTU").

Hardware Wiring

RS485 connection:

FlexiHAL A → VFD SG+
FlexiHAL B → VFD SG-
FlexiHAL GND → VFD GND/ACM

Motor cable shielding:

Ground shield at VFD end only — connect to VFD earth terminal ⊕
Leave spindle/motor end of shield floating
Grounding both ends creates a ground loop and worsens EMI

4th wire alongside U/V/W:

This is the PE/earth/ground wire for the motor chassis
Connect to VFD grounding terminal ⊕ (earth symbol) — NOT to U/V/W
Never leave unconnected — floating motor chassis is a shock hazard and EMI source

Modbus Communication Parameters

Parameter	Value
Baud rate	9600
Data bits	8
Stop bits	1 (8N1)
Parity	None
Slave address	1
Protocol	Modbus RTU

Critical: Factory default is 8N2 (F13.02=3). Must be changed to 8N1 (F13.02=0) for grblHAL compatibility. grblHAL has hardcoded 8N1 with no configurable override.

Modbus Register Map (empirically verified)

Register	Address (hex)	Address (decimal)	Function	Notes
Control word	`0x1000`	`4096`	Run/stop/reset	Write only
Frequency setpoint	`0x3000`	`12288`	Set speed as %	`-10000` to `+10000` = -100% to +100% of max freq
Frequency readback	`0x3001`	`12289`	Read actual freq	Units: 0.1Hz/unit. `8000` = 800.0Hz
Bus voltage	`0x3002`	`12290`	DC bus voltage	Read only

Critical note: Register 0x1001 is referenced in some online BD600 configs as the frequency setpoint. On this BD612 variant 0x3000 is the correct percentage-based setpoint. Register 0x1001 is the control word register — writing frequency values there has no effect on output frequency.

Control Word Values (`0x1000`)

Value (hex)	Value (decimal)	Meaning
`0x0001`	`1`	Run forward (CW)
`0x0002`	`2`	Run reverse (CCW)
`0x0005`	`5`	Stop (free coast)
`0x0006`	`6`	Stop (decelerate)
`0x0007`	`7`	Fault reset

Frequency Setpoint Scaling (`0x3000`)

Desired speed	Register value	Hex
24000rpm (800Hz, 100%)	`10000`	`0x2710`
12000rpm (400Hz, 50%)	`5000`	`0x1388`
6000rpm (200Hz, 25%)	`2500`	`0x09C4`
1000rpm (33.3Hz, 4.2%)	`417`	`0x01A1`

Frequency Readback Scaling (`0x3001`)

Register value	Actual frequency	RPM
`8000`	800.0Hz	24000rpm
`4000`	400.0Hz	12000rpm
`2000`	200.0Hz	6000rpm

mbpoll Commands (Windows, USB-RS485 on COM4)

Standard flags for all commands: -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1

Note: -1 = one-shot (exit after one poll). -q = quiet (suppress banner). Always use both. Note: mbpoll uses 1-based register addressing. Add 1 to hardware register address. e.g. hardware 0x3000 = mbpoll -r 0x3001. Note: grblHAL uses direct hardware addressing with no offset.

Test communication (read bus voltage)

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0x3003 -c 1 COM4

Set frequency (example: 50% = 12000rpm)

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0x3001 COM4 -- 0x1388

Run forward

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0x1001 COM4 -- 0x0001

Stop (decelerate)

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0x1001 COM4 -- 0x0006

Fault reset

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0x1001 COM4 -- 0x0007

Read actual running frequency and bus voltage

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0x3002 -c 2 COM4

Read F00 parameters (first 10)

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0xF001 -c 10 COM4

Read F02 motor parameters

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0xF201 -c 10 COM4

Read F13 communication parameters

mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0xFD01 -c 7 COM4

VFD Keypad Parameter Settings

F00 — Standard Function Parameters (confirmed values)

Parameter	Value	Hex	Meaning
`F00.00`	`2`	`0x0002`	V/F control mode
`F00.01`	`2`	`0x0002`	RS485 command source
`F00.02`	`0`	`0x0000`	Modbus run source
`F00.03`	`8000`	`0x1F40`	Max frequency = 800.0Hz
`F00.04`	`8000`	`0x1F40`	Upper frequency limit = 800.0Hz
`F00.05`	`0`	`0x0000`	Lower frequency limit = 0Hz
`F00.06`	`9`	`0x0009`	Frequency A source = RS485
`F00.07`	`0`	`0x0000`	Frequency B source = keypad
`F00.08`	`0`	`0x0000`	Frequency B range
`F00.09`	`0`	`0x0000`	Frequency source = A only
`F00.10`	`0`	`0x0000`	Keypad preset frequency = 0
`F00.11`	`1`	`0x0001`	Frequency resolution = 0.1Hz
`F00.12`	`1000`	`0x03E8`	Acceleration time = 10.0s
`F00.13`	`1000`	`0x03E8`	Deceleration time = 10.0s
`F00.22`	`9`	`0x0009`	Bind RS485 command to RS485 freq source

F00.10 warning: This parameter reverts to 800Hz on power cycle if not explicitly saved. If F00.22 is misconfigured and VFD falls back to keypad preset, spindle will run to full speed. Keep at 0 for safety.

F00.22 is critical: Without F00.22=9, the VFD display H value (setpoint) changes with Modbus frequency commands but the P value (actual output) does not respond — spindle runs at F00.10 preset instead. This was the key missing parameter.

F00.03 keypad limit: Maximum value accepted via Modbus write is limited by firmware to ~32000 (320Hz). Values above this return Invalid data. Set F00.03 via keypad directly. The keypad accepts up to 800.00Hz on this unit.

F02 — Motor 1 Parameters (confirmed values)

Parameter	Value	Hex	Meaning
`F02.00`	`0`	`0x0000`	Common asynchronous motor
`F02.01`	`45`	`0x002D`	Rated power = 4.5kW
`F02.02`	`8000`	`0x1F40`	Rated frequency = 800.0Hz
`F02.03`	`24000`	`0x5DC0`	Rated speed = 24000rpm
`F02.04`	`220`	`0x00DC`	Rated voltage = 220V
`F02.05`	`2000`	`0x07D0`	Rated current = 20.0A

F02.02 ordering: Must be set before F00.03. The drive enforces F00.03 ≤ F02.02 — if F02.02 is still at default 50Hz, F00.03 cannot be raised above ~320Hz via Modbus.

F04 — V/F Control Parameters (confirmed values)

Parameter	Value	Hex	Meaning
`F04.00`	`0`	`0x0000`	Linear V/F curve
`F04.01`	`1`	`0x0001`	Torque boost = 0.1%
`F04.02`	`500`	`0x01F4`	Torque boost cutoff = 50.0Hz
`F04.10`	`64`	`0x0040`	V/F over-excitation gain

F13 — Communication Parameters (confirmed values)

Parameter	Value	Hex	Meaning
`F13.00`	`1`	`0x0001`	Slave address = 1
`F13.01`	`5`	`0x0005`	Baud rate = 9600
`F13.02`	`0`	`0x0000`	Data format = 8N1
`F13.03`	`20`	`0x0014`	Response delay = 20ms
`F13.04`	`0`	`0x0000`	Timeout action
`F13.05`	`1`	`0x0001`	Standard Modbus protocol
`F13.06`	`0`	`0x0000`	Current resolution

F13.01 baud rate lookup:

Value	Baud rate
`0`	1200
`1`	2400
`2`	4800
`3`	7200
`4`	9600 — NOT this
`5`	9600 ← use this
`6`	19200
`7`	38400

F13.02 data format lookup:

Value	Format	Notes
`0`	`8N1`	Use this — matches grblHAL
`1`	`8E1`
`2`	`8O1`
`3`	`8N2`	Factory default — causes silent failure with grblHAL

Factory Reset Procedure

Navigate keypad to F00.28
Set to 1 (restore factory defaults, preserves motor params) or 2 (clear fault history only)
Press FUNC/DATA to confirm
Power cycle VFD
Re-enter all F00, F04, F13 parameters from this document
Motor parameters F02.01–F02.05 are preserved through factory reset

grblHAL MODVFD Settings (confirmed working)

Complete $ settings for spindle/Modbus

$10=11      ; Status report mask — REQUIRED for spindle speed reporting in ?
            ; Bit 0 (1) = MPos, Bit 1 (2) = Bf, Bit 3 (8) = FS feed+speed
            ; Without $10=11, ? never shows |FS:| field and spindle state is invisible

$30=24000   ; Max spindle speed (RPM)
$31=0       ; Min spindle speed (RPM)
$32=0       ; Laser mode = off
$39=0       ; Spindle at-speed input = disabled
$394=0      ; Spindle on delay = 0s

$370=0      ; Modbus stream = FlexiHAL onboard RS485 transceiver
            ; CRITICAL — other values route to wrong UART, nothing works

$374=2      ; Modbus baud rate = 9600
            ; CRITICAL — default is 3=19200, causes completely silent failure
            ; $376/$377/$378 return Error 53 (not available) — use $374 only

$395=5      ; Active spindle = MODVFD

$462=4096   ; Run/stop register = 0x1000
$463=12288  ; Frequency setpoint register = 0x3000 (percentage-based)
            ; NOT 0x1001 — that is the control word register on this variant
$464=12289  ; Frequency readback register = 0x3001
$465=1      ; Run forward command = 0x0001
$466=6      ; Run reverse command = 0x0006 (uses stop+reverse, not 0x0002)
$467=6      ; Stop command = 0x0006 (decelerate to stop)

$468=10000  ; RPM → register multiplier
$469=24000  ; RPM → register divider
            ; Formula: register = RPM × $468 / $469
            ; S24000 → 24000 × 10000/24000 = 10000 = 100% = 800Hz ✓
            ; S12000 → 12000 × 10000/24000 = 5000  = 50%  = 400Hz ✓
            ; S1000  → 1000  × 10000/24000 = 416   = 4.2% = 33Hz  ✓

$470=3      ; Readback RPM multiplier
$471=1      ; Readback RPM divider
            ; Formula: RPM = register_value × $470 / $471
            ; 4000 (400Hz) × 3/1 = 12000rpm ✓
            ; 8000 (800Hz) × 3/1 = 24000rpm ✓

$476=1      ; Modbus slave address = 1

Frequency scaling summary

`M3 S` value	Register sent	VFD display	Actual speed
`S24000`	`10000`	`P800.0`	24000rpm
`S12000`	`5000`	`P400.0`	12000rpm
`S6000`	`2500`	`P200.0`	6000rpm
`S1000`	`416`	`P33.3`	1000rpm

Status report

With $10=11, the ? response includes spindle state:

<Idle|MPos:x,y,z|Bf:128,1024|FS:0,12000>

FS:feed,spindle — spindle value shows commanded RPM. Actual RPM from readback register updates asynchronously.

MODVFD Plugin Behaviour (from modvfd.c source)

On M3 Sxxx, grblHAL calls spindleSetState()
First: writes run command ($465) to run/stop register ($462) — blocking FC06
Only if step 2 ACKs: writes frequency value to frequency register ($463) — blocking FC06
grblHAL withholds ok until both writes complete (up to 500ms, 5 retries each)
Periodic non-blocking FC03 reads from $464 update at-speed status asynchronously
Readback RPM = register_value × ($470 / $471)

Important: grblHAL <Idle state in ? response means no axis motion — it does NOT mean spindle is off. Spindle state is shown in |FS:| field only when $10=11.

Common Fault Codes

Code	Meaning	Common Cause	Fix
`E004`	Overcurrent during acceleration	Wrong V/F curve, accel too fast	Check motor params, increase `F00.12`
`E008`	AC drive overload	Wrong motor parameters	Correct `F02.01`–`F02.05`
`E032`	Current limit fault	V/F instability, torque boost too high	Set `F04.01=0`, check `F04.11`
`E034`	Speed deviation	Encoder feedback diverged from setpoint	Switch to V/F mode `F00.00=2`
`ALARM:1`	grblHAL hard limit	EMI from spindle triggering limit inputs	Shield cables, improve grounding
`ALARM:8`	Homing fail	Machine not homed, or in alarm state	`$X` then `$H`
`ALARM:14`	Spindle at-speed timeout	Modbus not communicating	Set `$470=0` while debugging

Debugging Procedure

If spindle does not respond to M3:

Verify $10=11 — without this ? shows no spindle state and debugging is blind
Test with mbpoll first — disconnect grblHAL, use mbpoll to confirm basic comms:
```
mbpoll -1 -q -m rtu -b 9600 -d 8 -s 1 -P none -a 1 -t 4:hex -r 0x3003 -c 1 COM4
```
Should return bus voltage ~0x0D00 (330V). If timeout: check wiring, check F13.02=0
Verify baud rate: F13.01=5 (9600) must match $374=2 (9600)
Verify stop bits: F13.02=0 (8N1) — factory default 3 (8N2) causes silent failure
Verify UART: $370=0 routes to FlexiHAL onboard RS485
Check F00.22=9 — without this, H value changes but spindle doesn't respond
Check F00.06=9 — RS485 must be selected as frequency source
Disable readback during debug: $464=0 prevents grblHAL from holding the bus
Watch VFD display: H = setpoint received, not running. P = running. H without P = run command not working

Known Limitations

Modbus frequency ceiling: F00.03 cannot be written above ~32000 (320Hz) via Modbus — firmware enforces signed 16-bit limit. Set via keypad (accepts up to 800.00Hz).
F00.10 reverts: Keypad preset frequency reverts to previous value on power cycle unless saved via EEPROM write. Keep at 0 as safety default.
grblHAL stop bits: MODVFD has hardcoded 8N1. $376/$377/$378 return Error 53. VFD must be set to F13.02=0.
grblHAL <Idle while running: Normal — means no axis motion, not spindle off. Use $10=11 and ? to see actual spindle state.
G4 dwell timeout in ncSender: ncSender has 1s ok timeout. G4 P2 (2s dwell) will show timeout warning but completes correctly — grblHAL sends ok after the dwell. Not a fault.
grblHAL continuous Modbus polling: With $464 set, grblHAL polls the readback register continuously, blocking mbpoll access. Set $464=0 before using mbpoll while grblHAL is connected.

References

LinuxCNC forum: "Vfdmod — An easy VFD control over MODBUS RTU" — BD600 config by user H2B
grblHAL Plugins_spindle: https://github.com/grblHAL/Plugins_spindle
Expatria Technologies FlexiHAL: https://github.com/Expatria-Technologies/Flexi-HAL
BD600 Series manual: Zhejiang New Folinn Electric Co., Ltd

All settings verified via mbpoll and grblHAL on 2026-05-17. Settings marked CRITICAL were confirmed to cause silent failure when incorrect.

leehambley/Folinn | Fuling BD612 Series VFD — grblHAL MODVFD Setup Guide.md

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Folinn / Fuling BD612 Series VFD — grblHAL MODVFD Setup Guide

Background

Hardware Wiring

Modbus Communication Parameters

Modbus Register Map (empirically verified)

Control Word Values (`0x1000`)

Frequency Setpoint Scaling (`0x3000`)

Frequency Readback Scaling (`0x3001`)

mbpoll Commands (Windows, USB-RS485 on COM4)

Test communication (read bus voltage)

Set frequency (example: 50% = 12000rpm)

Run forward

Stop (decelerate)

Fault reset

Read actual running frequency and bus voltage

Read F00 parameters (first 10)

Read F02 motor parameters

Read F13 communication parameters

VFD Keypad Parameter Settings

F00 — Standard Function Parameters (confirmed values)

F02 — Motor 1 Parameters (confirmed values)

F04 — V/F Control Parameters (confirmed values)

F13 — Communication Parameters (confirmed values)

Factory Reset Procedure

grblHAL MODVFD Settings (confirmed working)

Complete $ settings for spindle/Modbus

Frequency scaling summary

Status report

MODVFD Plugin Behaviour (from modvfd.c source)

Common Fault Codes

Debugging Procedure

Known Limitations

References

leehambley/Folinn | Fuling BD612 Series VFD — grblHAL MODVFD Setup Guide.md

Folinn / Fuling BD612 Series VFD — grblHAL MODVFD Setup Guide

Background

Hardware Wiring

Modbus Communication Parameters

Modbus Register Map (empirically verified)

Control Word Values (0x1000)

Frequency Setpoint Scaling (0x3000)

Frequency Readback Scaling (0x3001)

mbpoll Commands (Windows, USB-RS485 on COM4)

Test communication (read bus voltage)

Set frequency (example: 50% = 12000rpm)

Run forward

Stop (decelerate)

Fault reset

Read actual running frequency and bus voltage

Read F00 parameters (first 10)

Read F02 motor parameters

Read F13 communication parameters

VFD Keypad Parameter Settings

F00 — Standard Function Parameters (confirmed values)

F02 — Motor 1 Parameters (confirmed values)

F04 — V/F Control Parameters (confirmed values)

F13 — Communication Parameters (confirmed values)

Factory Reset Procedure

grblHAL MODVFD Settings (confirmed working)

Complete $ settings for spindle/Modbus

Frequency scaling summary

Status report

MODVFD Plugin Behaviour (from modvfd.c source)

Common Fault Codes

Debugging Procedure

Known Limitations

References

Control Word Values (`0x1000`)

Frequency Setpoint Scaling (`0x3000`)

Frequency Readback Scaling (`0x3001`)