HotEndController

ESP32-C3 autonomous secondary hotend controller for a retrofitted Qidi Max3 with an EBB2209 (RP2040) CAN-bus toolhead.

Both heaters run simultaneously — Klipper controls the primary extruder as normal, while the ESP32-C3 independently reads a PT1000, runs PID, and drives a second heater via MOSFET/SSR.

Hardware

• Qidi Max3 — MKS SKIPR (STM32F407) main board
• EBB2209 (RP2040) — CAN-bus toolhead MCU
• ESP32-C3 SuperMini with OLED — AliExpress
• PT1000 RTD — secondary hotend temperature sensor
• MOSFET or SSR — driven by ESP32 GPIO10 (3.3 V logic)
• 1 kΩ reference resistor for PT1000 voltage divider
• 4.7 kΩ pull-ups on I2C SDA/SCL (if not on dev board)

See ESP32C3wOLED/pinout.md for full wiring diagrams.

Repository Structure

├── printer.cfg                     Entry point — select Factory, Stock, or MyMod
├── Factory/                        Original Qidi Max3 configs (REFERENCE ONLY)
├── MyMod-03012026/                 Modular Klipper config for EBB2209 toolhead
│   ├── Qidi-Max3-MyMod-EBB-RP-double.cfg  Dual heater (EBB2209 + ESP32 hotend2)
│   ├── Qidi-Max3-MyMod-EBB-RP-single.cfg  Single heater (EBB2209 only)
│   ├── esp32_temp_display.py       Klipper extra — bidirectional I2C with ESP32
│   ├── ESP-PT1000-2.cfg            Hotend2 config + M104/M109 macros
│   └── …                          Kinematics, heaters, fans, sensors, macros
└── ESP32C3wOLED/                   ESP-IDF firmware for the ESP32-C3
    ├── AI-Instruct.md              Detailed project instructions
    ├── pinout.md                   Wiring, I2C protocol, PT1000 circuit
    └── main/                       Firmware source (PID, I2C, ADC, OLED)

Installation on the Printer

1. Copy config files to the printer

SSH into your Qidi Max3 (default user mks, typically at mks@your-printer-ip):

# From your PC, copy the config directories to the printer
scp -r MyMod-03012026 mks@<printer-ip>:~/klipper_config/
scp -r Factory mks@<printer-ip>:~/klipper_config/

2. Replace printer.cfg

Back up the existing printer.cfg first, then copy ours:

# On the printer (via SSH)
cd ~/klipper_config
cp printer.cfg printer.cfg.bak       # backup original

# From your PC
scp printer.cfg mks@<printer-ip>:~/klipper_config/printer.cfg

The new printer.cfg is a selector — it includes one of four configurations:

Option	Line to uncomment	Description
Factory	[include Factory/printer.cfg]	Original monolithic Qidi config
MyMod (dual)	[include MyMod-03012026/Qidi-Max3-MyMod-EBB-RP-double.cfg]	EBB2209 CAN toolhead + ESP32 hotend2
MyMod (single)	[include MyMod-03012026/Qidi-Max3-MyMod-EBB-RP-single.cfg]	EBB2209 CAN toolhead only — no ESP32
Stock	[include MyMod-03012026/Qidi-Max3-STOCK-main.cfg]	Original MKS_THR toolhead (modular split)

By default, MyMod dual (EBB2209 + ESP32) is active. To switch, edit printer.cfg and uncomment the desired [include] line (comment out the others).

The second heating element is designed to be easy to attach and remove. When it is physically connected, use MyMod (dual). When it is removed, switch to MyMod (single) to avoid I2C errors.

Note: Factory mode is standalone — comment out the [mcu] and [include Factory/Adaptive_Mesh.cfg] shared section when using it.

3. Install the Klipper extra (dual-heater mode only)

The ESP32 hotend controller needs a custom Klipper module. Skip this step if using MyMod (single) or Stock mode.

# On the printer (via SSH)
cp ~/klipper_config/MyMod-03012026/esp32_temp_display.py ~/klipper/klippy/extras/
sudo systemctl restart klipper

4. Build and flash the ESP32-C3 firmware

Requires ESP-IDF (v5.x recommended):

cd ESP32C3wOLED
idf.py set-target esp32c3
idf.py build
idf.py -p COMx flash monitor    # replace COMx with your serial port

5. Wire the ESP32-C3 to the EBB2209

Connect the I2C bus between the EBB2209 and ESP32-C3:

EBB2209 RP2040	ESP32-C3	Function
gpio4	GPIO8	I2C SDA
gpio5	GPIO9	I2C SCL
GND	GND	Ground
3V3 (optional)	3V3	Power (if not self-powered)

See pinout.md for the PT1000 and MOSFET wiring.

6. Verify

After restarting Klipper:

# In Fluidd/Mainsail console:
SET_HOTEND2_TEMP              # should report actual=xx.x°C target=0.0°C
SET_HOTEND2_TEMP S=100        # set secondary hotend to 100°C
HOTEND2_OFF                   # turn it off

Hotend2 temperature should appear in the Fluidd/Mainsail dashboard.

GCode Commands

Command	Description
SET_HOTEND2_TEMP S=200	Set secondary hotend target (non-blocking)
SET_HOTEND2_TEMP	Query current temps
HOTEND2_OFF	Turn off secondary hotend
M104_HOTEND2 S=200	Non-blocking set (like M104)
M109_HOTEND2 S=200	Blocking wait until reached (like M109)
WAIT_HOTEND2	Block until current target ±3°C

Slicer start G-code

Set both heaters in your slicer's start G-code:

M104 S250                ; primary extruder
M104_HOTEND2 S=200       ; secondary hotend
M140 S60                 ; bed
M109 S250                ; wait for primary
M109_HOTEND2 S=200       ; wait for secondary

Safety Features

• I2C watchdog — heater off after 30 s with no communication
• Over-temperature — hard limit at 360°C
• Sensor fault — open/short circuit detection
• Thermal runaway (not heating) — faults if duty ≥50% for 120 s with <10°C rise
• Thermal runaway (falling away) — faults if temp drops >15°C below target for 20 s (after initial reach)
• All faults are latching — heater stays off until power cycle

License

Private project.