Complete Klipper configuration for the Mellow LLL Filament Plus Buffer with automatic filament feeding and buffer management.

Note: This is the Klipper configuration. For the Buffer Plus firmware source code, see the main repository README.

• ✅ Automatic Buffer Control - Fills buffer automatically when filament is detected
• ✅ Smart Feed Bursts - HALL2 sensor triggers small feed bursts during printing
• ✅ Overfill Protection - HALL1 prevents buffer from jamming into extruder
• ✅ Manual Feed/Retract - Physical buttons for manual filament loading
• ✅ Filament Runout Detection - Optional pause on filament runout

• ENDSTOP3 (PB7): Filament entrance sensor - detects when filament is loaded
• HALL3 (PB4): Initial fill sensor - switches from continuous to burst mode
• HALL2 (PB3): Primary buffer control - triggers feed bursts when neck extends
• HALL1 (PB2): Overfill limiter - prevents buffer from over-filling

• Feed Button (PB12): Manual continuous feed (hold to feed)
• Retract Button (PB13): Manual continuous retract (hold to retract)

Katapult (formerly CanBoot) allows easy firmware updates without needing to press physical buttons or enter DFU mode.

cd ~
git clone https://github.com/Arksine/katapult
cd katapult
make menuconfig

Katapult Configuration:

• Micro-controller Architecture: STMicroelectronics STM32
• Processor model: STM32F072
• Build Katapult deployment application: Do Not build
• Clock Reference: 8 MHz crystal
• Communication interface: USB (on PA11/PA12)
• Application start offset: 8KiB offset
• USB ids: Leave default or customize
• Support bootloader entry on rapid double click: [*] ✓ (Enable this!)
• Enable bootloader entry on button (or gpio) state (Do not enable this)
• Enable Status LED [*]
• (PA8) Status LED GPIO Pin

make clean
make

The LLL Buffer Plus needs to be put into DFU (Device Firmware Update) mode:

Method 1: Jumper BOOT0 to 3.3V

1. Push and hold the boot button
2. Push the reset button
3. Release the boot button

Method 2: BOOT Button (if accessible)

1. Disconnect USB
2. Hold the BOOT button on the board
3. Connect USB while holding BOOT
4. Release BOOT button

lsusb | grep DFU

You should see something like:

Bus 001 Device 015: ID 0483:df11 STMicroelectronics STM Device in DFU Mode

If not detected, try:

sudo dfu-util -l

cd ~/katapult
sudo dfu-util -a 0 -D ~/katapult/out/katapult.bin --dfuse-address 0x08000000:force:mass-erase:leave -d 0483:df11

You should see output ending with:

File downloaded successfully

Disconnect and reconnect USB. Check for Katapult device:

ls /dev/serial/by-id/

You should see something like:

usb-katapult_stm32f072xb_XXXXXX-if00

cd ~/klipper
make menuconfig

Klipper Configuration:

• Micro-controller Architecture: STMicroelectronics STM32
• Processor model: STM32F072
• Bootloader offset: 8KiB bootloader (for Katapult)
• Clock Reference: 8 MHz crystal
• Communication interface: USB (on PA11/PA12)

Important: The bootloader offset MUST match what you set in Katapult (8KiB)!

make clean
make

Find your device ID:

ls /dev/serial/by-id/

Flash using Katapult's flashtool:

python3 ~/katapult/scripts/flashtool.py -f ~/klipper/out/klipper.bin -d /dev/serial/by-id/usb-katapult_stm32f072xb_XXXXXX-if00

Or using make flash:

make flash FLASH_DEVICE=/dev/serial/by-id/usb-katapult_stm32f072xb_XXXXXX-if00

You should see:

Attempting to connect to bootloader
Katapult Connected
Protocol: 1.0.0
Flashing '/home/pi/klipper/out/klipper.bin'...
[##################################################]
Write complete: X pages
Verifying...
Verification Complete
CRC: 0xXXXXXXXX
Flashing successful

Disconnect and reconnect USB. Check the device ID changed:

ls /dev/serial/by-id/

You should now see:

usb-Klipper_stm32f072xb_XXXXXX-if00

cp mellow.cfg ~/printer_data/config/

Add to your main printer.cfg:

[include mellow.cfg]

Edit mellow.cfg and update the serial path:

[mcu LLL_PLUS]
serial: /dev/serial/by-id/usb-Klipper_stm32f072xb_XXXXXX-if00
restart_method: command

Replace XXXXXX with your actual device ID from Step 2.3.

FIRMWARE_RESTART

Check the Klipper web interface - you should see the LLL_PLUS MCU connected!

If you prefer not to use Katapult, you can flash Klipper directly:

cd ~/klipper
make menuconfig

Settings:

• Micro-controller Architecture: STMicroelectronics STM32
• Processor model: STM32F072
• Bootloader offset: No bootloader
• Clock Reference: 8 MHz crystal
• Communication interface: USB (on PA11/PA12)

make clean
make

1. Enter DFU mode (see Step 1.2)
2. Flash:

   make flash FLASH_DEVICE=0483:df11

Note: Without Katapult, future firmware updates will require entering DFU mode manually each time.

1. Insert filament into entrance sensor (ENDSTOP3/PB7)
2. Buffer starts continuous feeding automatically
3. When neck reaches top (HALL3 triggers), switches to burst mode

1. Printer pulls filament → Buffer neck extends
2. When neck reaches mid-point (HALL2 releases) → 15mm feed burst
3. Neck retracts back into housing
4. Repeat as needed

1. If buffer overfills and neck extends too far (HALL1 releases)
2. Auto-feed pauses until neck retracts
3. Prevents jamming against extruder

Change the burst size in _BUFFER_FEED_BURST macro:

[gcode_macro _BUFFER_FEED_BURST]
gcode:
    {% if printer["gcode_macro _BUFFER_AUTO_CONTROL"].overfill_lock == 0 %}
        ACTIVATE_EXTRUDER EXTRUDER=extruder1
        M83
        G1 E15 F3000  # ← Change E15 to desired burst amount (mm)
        M118 Buffer: Feed burst complete
    {% endif %}

Change feed/retract speed (currently 3000 mm/min = 50 mm/s):

G1 E10 F3000  # Change F3000 to desired speed (mm/min)

Common speeds:

• F1800 = 30 mm/s (slower, more reliable)
• F3000 = 50 mm/s (default)
• F6000 = 100 mm/s (faster, may skip)

Adjust TMC2208 current if motor is too weak or overheating:

[tmc2208 extruder1]
uart_pin: LLL_PLUS:PB1
run_current: 0.35  # Increase up to 0.5 if motor skips, decrease to 0.25 if overheating
stealthchop_threshold: 999999

To calibrate your buffer motor for accurate feeding:

1. Mark the filament 120mm from the entrance sensor

2. Heat your hotend (if min_extrude_temp is set)

3. Activate the buffer extruder:

   ACTIVATE_EXTRUDER EXTRUDER=extruder1
   

4. Feed 100mm:

   M83
   G1 E100 F300
   

5. Measure the actual distance the mark moved

6. Calculate new rotation distance:

   new_rotation_distance = current_rotation_distance * (100 / actual_distance_moved)
   

   Example: If mark moved 95mm instead of 100mm:

   new_rotation_distance = 18.86 * (100 / 95) = 19.85
   

7. Update config:

   [extruder1]
   rotation_distance: 19.85  # Your calculated value

8. Restart and test again until accurate

DFU device not detected:

• Check USB cable (must be data cable, not charge-only)
• Try different USB port
• Check lsusb without grep to see all devices
• Verify BOOT0 is properly jumpered to 3.3V
• Try both BOOT button methods

"Cannot open DFU device":

sudo dfu-util -a 0 -D ~/katapult/out/katapult.bin --dfuse-address 0x08000000:force:mass-erase:leave -d 0483:df11

Run with sudo if permission denied.

Katapult not appearing after flash:

• Disconnect and reconnect USB
• Wait 5-10 seconds
• Check dmesg | tail for USB events
• Reflash Katapult - it may not have written correctly

Klipper flash fails via Katapult:

• Verify bootloader offset matches (8KiB in both Katapult and Klipper)
• Try entering Katapult manually: Double-tap reset button quickly
• Reflash Katapult and try again

Buffer feeds continuously and won't stop:

• Check HALL3 sensor is working: QUERY_ENDSTOPS
• Verify neck can physically reach HALL3 when extended
• Check sensor wiring and polarity
• Look for "HALL3 TRIGGERED" message in console

HALL2 bursts happen too frequently:

• Increase burst amount (E15 → E20 or E25)
• Check reverse bowden tube tension
• Verify printer is actually consuming filament

Buffer overfills (HALL1 warning):

• Decrease burst amount (E15 → E10)
• Check that printer is pulling filament from buffer
• Verify no clogs in bowden tube
• Check extruder is actually feeding

Manual buttons don't work:

• Verify button wiring to PB12 (feed) and PB13 (retract)
• Check console for "button pressed/released" messages
• Ensure buttons are wired normally-open (NO)
• Test with QUERY_ENDSTOPS while pressing

MCU not detected after flashing Klipper:

• Verify Klipper firmware is flashed (not Arduino or Katapult)
• Check USB connection
• Run ls /dev/serial/by-id/ to find device
• Check dmesg | tail for USB enumeration errors
• Reflash Klipper firmware

"Option 'step_pin' is not valid in section 'extruder X'":

• Ensure section is named [extruder1] not [extruder filament_buffer]
• Klipper only supports numbered extruders: extruder, extruder1, extruder2, etc.

TMC UART errors:

• Verify UART pin is correct: uart_pin: LLL_PLUS:PB1
• Check TMC2208 is properly seated
• Verify run_current is not too low (minimum ~0.2)

Once Katapult is installed, updating Klipper is easy:

1. Rebuild Klipper:

   cd ~/klipper
   make clean
   make

2. Flash via Katapult:

   python3 ~/katapult/scripts/flashtool.py -f ~/klipper/out/klipper.bin -d /dev/serial/by-id/usb-Klipper_stm32f072xb_XXXXXX-if00

3. Or use double-tap reset:

   • Quickly press reset button twice
   • Device enters Katapult mode for 5 seconds
   • Flash using the Katapult device ID

No need to open the case or press BOOT buttons! 🎉

Klipper configuration developed by @ss1gohan13 for the Mellow LLL Filament Plus Buffer.

Hardware and original firmware by Mellow 3D.

Special thanks to:

• James on the Klipper Discord
• Ian on the Klipper Discord
• Arksine for Katapult bootloader
• Klipper team

MIT License - Feel free to use and modify!