Bigtreetech Scylla V1 firmware installation.

[PFarm]

34 minutes ago, hpmax said:

First, there is a 24V fan.  Is there a way to hook it up to the Scylla either as 12V or VMOS?  I think if I ever put in a 48V supply, I'll want to switch to a 12V fan since there will no longer be 24V and I don't think people make 48V fans.

Second, what is the recommended way to control the spindle power supply.  The 48V power supply has a 3 terminal wiring harness coming off it , where black is ground, blue is the wiper and red is 5V.  However, the black wire is hard tied to the 48V supply ground.  The Scylla's 24V power supply ground isn't connected to the spindle's power supply ground, and I don't know if it's safe to connect them together (it probably is, because if they were both hard tied to something then it would be showing they were connected).  That said, is there a proper/safe way to connect the Scylla to the 3-terminal interface.  Do I connect blue (wiper) to AVR and black (ground) to SP-GND?

Thanks!

The VMCU doesn't support 12V input, 24V to 56V @ 10A. For fan control, you'd supply 24V to VMOS, which supplies power to the Aux 0-2 terminals. You assign which Aux port will control your fan(s).

 

When you say spindle, is it powered by a VFD or is it a router, which I believe is the latter since you're controlling speed via potentiometer. The best way to control the router is by using the onboard relay. You would wire the ground to the relay in and the relay out back to your router. The relay control IO pin PD5 would be configured in the userconfig.g file, which turns the router on and off. I'd also recommend that you purchase a contactor to control the power supplied to the router and stepper motor power supply. This would be wired to the e-stop, and in the userconfig.g file, you would control when the contactor would be active. Ex you hit the estop to stop the mill, you rest the estop switch, but the contactor remains powered off until you give the M80 command to enable it. It's to ensure that when the estop is reset, the steppers will not move or the router spin until everything is safe and you enable them.

 

 

I'd also recommend that you get microswitches for your endstops and wire them normally closed. Don't worry about hijacking this thread, it's all good. But you could also start your own for others to see how you've solved some of your issues.

 

 

Edited July 13, 2025 by PFarm

[hpmax]

On 7/13/2025 at 3:05 PM, PFarm said:

The VMCU doesn't support 12V input, 24V to 56V @ 10A. For fan control, you'd supply 24V to VMOS, which supplies power to the Aux 0-2 terminals. You assign which Aux port will control your fan(s).

 

When you say spindle, is it powered by a VFD or is it a router, which I believe is the latter since you're controlling speed via potentiometer. The best way to control the router is by using the onboard relay. You would wire the ground to the relay in and the relay out back to your router. The relay control IO pin PD5 would be configured in the userconfig.g file, which turns the router on and off. I'd also recommend that you purchase a contactor to control the power supplied to the router and stepper motor power supply. This would be wired to the e-stop, and in the userconfig.g file, you would control when the contactor would be active. Ex you hit the estop to stop the mill, you rest the estop switch, but the contactor remains powered off until you give the M80 command to enable it. It's to ensure that when the estop is reset, the steppers will not move or the router spin until everything is safe and you enable them.

 

I'd also recommend that you get microswitches for your endstops and wire them normally closed. Don't worry about hijacking this thread, it's all good. But you could also start your own for others to see how you've solved some of your issues.

Thanks for the quick reply, however, I'll be honest, I think you may have misread both questions, so let me try to restate:

1) Regarding the fan, I am currently using a 24V power supply to power the Scylla board, and a 24V fan.  I am considering switching to a 48V power supply (for the V-MCU/V-Motor).  If I do, I will no longer have a 24V power supply to power the fan, I will only have the 48V.  I don't think I can get a 48V fan, so the question is, can I get either 12V or 24V @ 200mA out of the Scylla board given 48V-in on VMOS/V-MCU/V-Motor.  Essentially I am hoping there is a step-down buck converter on the board that I can use to power the fan.  If I can't do that, I'll have to get a separate step down converter and this question sort of becomes moot.  Right now, the fan is not thermostatically controlled, it's simply on when the power supply is on, so it's wired direct to the power supply.

2) Regarding the spindle, yes, it's a "router."  The spindle is a DC motor which is powered by a DC power supply. The power supply has a potentiometer on it to control speed, that is provided with 0 and 5V, and returns a voltage between 0-5V on the wiper.  The supply output voltage is varied between 0-48V based on the wiper voltage. I would like to use the SP-GND/SPD/AVR connections on the Scylla board to emulate that potentiometer.  That is the spindle power supply provides a ground to SP-GND, 5V to AVR, and SPD will put out an analog signal that varies between SP-GND and AVR.  The catch here is that SP-GND (and the others) must be electrically isolated from Scylla's V-MCU/V-Motor/V-MOS ground as the two power supplies are not tied together, and I don't want to do that if I don't have to as I don't know if I can.  My goal here is to control the speed of the motor, not just if its on or off.

As an electrical engineer, this scares me, because this could be very dangerous or perfectly safe, depending on how the Scylla is designed and without seeing the schematic, it's hard to know which.  I can see optoisolators, next to the section, so that's definitely good.  I would think the proper way for BTT to have done this is to provide a digital PWM signal to the opto-isolators, and then the output of the optoisolators are powered by SP-GND and AVR, and some sort of D/A powered by SP-GND/AVR is used on the opto-isolated PWM supplied by the MCU.  But...For example, does the output go from 0-10V, or 0-AVR?  Is there a max voltage on AVR?  A min voltage on AVR? It's not real clear on this.

Ideally, the SP-EN would be used to control a SPDT relay, which would switch between the power supply (when turned on) and ground (when off in order to brake) -- with a reverse biased diode on the power supply output for safety -- but I'm not sure it's absolutely necessary, I think when you put 0V on the wiper the output voltage goes to 0V and that should brake the motor.

3) E-stop is wired to the A-MIN limit switch.  I will likely not wire in end-stops for X,Y,Z.  This isn't a high-end device, and I was looking for a simple project to make the router more usable vs the original parallel port control.  Is there a reason I can't reliably use the over-current detects in the TMC2160 to detect hittng an end-stop?  That actually works better on the Z-axis since this could detect hitting the work-piece regardless of it's actual location.

 

[PFarm]

Sorry, I misread your questions. There is no onboard buck converter on the Scylla. You mentioned wiring VMOS, VMCU and VMotor to 48V. Why not use your existing 24V PSU in VMOS? This way, the three AUX terminals can be used to supply 24V to components.

For your router, the connections listed below are for a VFD, not sure if it will do what you want it to do. AVR do supply o-10V. I'd suggest you join Discord Millennium Machine, there's a #BTT-Scylla-V1 section, and if you ping @Nine Miles, he should be able to answer your question. Just be aware that he has a newborn and may be a little slow at replying.

 

From what I can remember, I believe that most of the terminals are optoisolators except for the UART and I/O ports.

[hpmax]

6 hours ago, PFarm said:

Sorry, I misread your questions. There is no onboard buck converter on the Scylla. You mentioned wiring VMOS, VMCU and VMotor to 48V. Why not use your existing 24V PSU in VMOS? This way, the three AUX terminals can be used to supply 24V to components.

For your router, the connections listed below are for a VFD, not sure if it will do what you want it to do. AVR do supply o-10V. I'd suggest you join Discord Millennium Machine, there's a #BTT-Scylla-V1 section, and if you ping @Nine Miles, he should be able to answer your question. Just be aware that he has a newborn and may be a little slow at replying.

From what I can remember, I believe that most of the terminals are optoisolators except for the UART and I/O ports.

The original router hardware was pretty simple, there were 4 stepper drivers and a parallel port interface.  The only accessory was the fan.  It's likely the Scylla is *WAY* overkill, but the plan was to convert 3 machines and I wanted something in common that would work for everything. Using a separate 8 amp 24V power supply for a 150mA fan seems ridiculous.  Big, heavy, and inefficient.  I can't fit 3 power supplies in the controller box.  So, I'm better off just using a small cheap AliExpress buck converter to run the fan.

It would be nice to get schematics, or some support from BTT.

I'll check out the Discord... Thanks again.

[hpmax]

Nine Mile was very helpful!  He gave me a copy of the schematic.  So the 12V that is mentioned in the documentation does in fact come from a step-down buck converter, and it's good to 2.5 amps, so there should be no issue using a 12V fan if I can figure a 12V place to hook it up to.

The spindle control, looks good, except for one thing.  It's much as I imagined it.  The PWM signal goes through an opto-isolator, and is then goes through a dual op-amp.  The first op-amp adjusts the signal level, the second op-amp acts as a 1.6Hz low-pass filter, but there are two problems:

1) IIf you aren't using the Enable signal. it could take 4-5 seconds to turn the spindle on and off.  Turning on isn't that awful, but there should be a fast shut off, and there isn't unless you have some way of using the enable signal.

2) They used a pretty low-end op-amp which can probably only get within 1V of the rail, which means it'll work great up to 1V below the AVR voltage, and then it will just have a softens out, so I probably can only get 80% power.

[PFarm]

That's great that Nine Miles was able to help you. He was the one working with BTT designing the Scylla board.

[stefan63]

On 1/30/2025 at 9:47 PM, Stevo said:

Hi all and please to be part of the group.

I'm hoping there maybe someone who van help me make a start on installing the firmware on my board which will be running a cnc mill please.

I love new technology but struggle finding supporting literature that makes for straight forward instruction.

If theirs anyone who can get me started be very much appreciated.

Looking forward to a 6 or 8 driver version of the Scylla board that would make it much more versaile for dual spindle/Z axis and or tool changer setups.

[Stevo]

Hi all,

Hope you are all well ? 

Glad to be getting back to tinkering with the CNC, family health issues had put an abrupt stop to tinker time !

I'm hoping to be able to connect the spindle to the Scylla as at the moment i just manually control the spindle via the little control panel.

Is it literally the five wires to be able to do this or have settings in config and vfd to be altered.

 

Edited April 2 by Stevo

[PFarm]

@Stevo  Welcome back!

[Stevo]

Hello my friend good to be back and get stuck in. 

[Stevo]

10 hours ago, PFarm said:

@Stevo  Welcome back!

Trust me to have a VFD that does not conform 

[Stevo]

[Stevo]

[Stevo]

Looking through your build this looks to be in the ball park

 

Edited April 3 by Stevo

[PFarm]

Yes, I have the same VFD, and you're showing the correct connections. There is also a jumper on the VFD. Note there's a typo; it should read 1-2.

 

 

[Stevo]

 

Hey, a lot of head scratching going on here could do with a sanity check please 

 

 

[Stevo]

20 minutes ago, PFarm said:

Yes, I have the same VFD, and you're showing the correct connections. There is also a jumper on the VFD. Note there's a typo; it should read 1-2.

 

Thank you need to swap that over and add the jumper to ao does my wiring look correct please 

 

[PFarm]

Let me take a photo of my connections.

[Stevo]

1 minute ago, PFarm said:

Let me take a photo of my connections.

Fantastic thank you

 

[Stevo]

Have moved the jumper on the VFD and added the AO jumper now

[PFarm]

Ignore the DRV - 24V connection that powers a relay for my water-cooled pump and rad fans. You need to move the VO to VI

[Stevo]

Thank you

 

Edited April 3 by Stevo

[Stevo]

Thank you

 

 

Edited April 3 by Stevo

[Stevo]

55 minutes ago, PFarm said:

Ignore the DRV - 24V connection that powers a relay for my water-cooled pump and rad fans. You need to move the VO to VI

 

Hi i have the following 

BOARD = VFD

EN = FOR

DIR = REV

AVR = 10V

SP-G = ?

SPD = V1

COM = ?

Black wires are throwing me as to where they go to on the VFD 

DCM and ACM remain to be connected to Scylla not sure which is which

 

Edited April 3 by Stevo

[PFarm]