Standalone iHeater Firmware

iHeater is a compact and affordable solution for 3D printers without an active heated chamber or with limited connection options to the mainboard. It's especially useful for printers with proprietary boards lacking free ports for fans, heaters, or thermistors. iHeater solves this with a simple and universal approach.

It can operate standalone with its own firmware or be integrated with Klipper over USB.

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About the Firmware

iHeater is firmware for a standalone device that manages the temperature of a 3D printer's heated chamber.

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Purpose

The device ensures heating and stable temperature maintenance inside the printer's chamber, which is critical for printing ABS, ASA, and other shrinkage-sensitive and adhesion-sensitive filaments.

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How to Configure the Firmware

File config.h

This file contains all configurable parameters:

Parameter	Description
SELECTED_THERMISTOR_TYPE	Select thermistor type (0-5, see below)
MODE_TEMP_0-MODE_TEMP_7	Setpoint temperatures for each mode. Can be any float value, e.g. MODE_TEMP_4 67.5
MAX_TEMP, MIN_TEMP	Allowed temperature range for the heater
MAX_AIR_TEMP, MIN_AIR_TEMP	Allowed temperature range for air
HEATER_MIN_PWM	Minimum PWM required to start heater response monitoring
HEATER_RESPONSE_TIMEOUT_MS	Timeout for detecting heater response (default 5 seconds)
AIR_TARGET_TIMEOUT_MS	Maximum time allowed to reach air target temperature (default 10 minutes)
TIMER_CLOCK, PWM_FREQUENCY, PWM_STEPS	PWM configuration (frequency and resolution)

Thermistors

Selected using SELECTED_THERMISTOR_TYPE:

ID	Type	Notes
0	ATC Semitec 104GT-2	Standard used by E3D
1	ATC Semitec 104NT-4-R025H42G	104GT alternative
2	EPCOS 100K B57560G104F	Widely used
3	Generic 3950	Default, common Chinese type
4	SliceEngineering 450	High-temp support
5	TDK NTCG104LH104JT1	Medical-grade accuracy

Temperature Modes and LEDs

Each mode sets a target temperature and is displayed via binary LEDs:

When entering the mode, the LEDs blink, once the mode is activated, they remain constantly lit.

Mode	Temperature	LED3	LED2	LED1
MODE_TEMP_0	0.0°C
MODE_TEMP_1	55.0°C
MODE_TEMP_2	60.0°C
MODE_TEMP_3	65.0°C
MODE_TEMP_4	70.0°C
MODE_TEMP_5	75.0°C
MODE_TEMP_6	80.0°C
MODE_TEMP_7	85.0°C

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Automatic enabling and disabling r1.1

Macros

#define TRIGGER_ON_TEMP  45.0f
#define TRIGGER_OFF_TEMP 80.0f
#define TRIGGER_MODE MODE_2

These parameters define the activation and deactivation temperatures for the heater, as well as the mode to be enabled upon activation.

Assuming the trigger thermistor is located near the heated bed. With the current settings, the chamber heater will turn on when the bed temperature reaches 45°C and will turn off when the bed temperature drops below 80°C. These parameters are suitable for most filaments that require an actively heated chamber and do not cause logical conflicts during operation.

It is also possible to select the mode that will be activated when the trigger is engaged. For example, TRIGGER_MODE MODE_2 is currently selected, which means that MODE_TEMP_2 will be activated, setting the chamber temperature to 60.0°C.

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Working with iHeater-link (r1.1 pulse build)

The iheater_rev1_1_pulse build is designed to pair with the ESP-based iHeater-link module. The module receives commands from the printer, a portal, or a mobile application and forwards the chamber setpoint to iHeater over a single GPIO line. The iHeater firmware is transport-agnostic — it only reads a number: the desired chamber air temperature in °C.

Wiring

1. Flash iHeater with the iheater_rev1_1_pulse build (see "How to Flash the Firmware").
2. Connect the signal wire from iHeater-link to the TH2 connector on the iHeater board (pin PB1).
3. A common GND between the ESP and iHeater is mandatory — use a dedicated ground wire.
4. Keep the heater thermistor on its usual TH0 connector. Keep the air thermistor on TH1. Both work exactly as in any other build.
5. The trigger connector is not used in this build (its line is repurposed as the digital input).

Never connect or disconnect the signal wire with power applied.

Accepted commands

Code from iHeater-link	Meaning
0	Heater off
10	Heater off (agreed "off-code")
45..90	Heater on, air setpoint equals the code in °C
Any other value	Ignored; previous state is kept

The minimum 45 °C is defined in config.h as PULSE_MIN_TARGET. The maximum is bounded by MAX_AIR_TEMP (90 °C by default).

LED indication

State	LED1	LED2	LED3
Waiting for the first frame after boot (up to 20 s)	chasing light LED1 → LED2 → LED3 with a 1000 ms step
Link OK, heating off	solid on (link-alive heartbeat)	off	short ~80 ms flash on every accepted frame
Link OK, heating on	chasing light LED1 → LED2 → LED3 with a 500 ms step
Link lost (>1.5 s with no frame after the first one)	All three blink together; the device resets with error code 0x08 (ERROR_LINK_LOST). The heater stays off.

Standard faults (overheat, open thermistor, heater-no-response) work exactly as in analog builds — see "Error Handling".

Link-lost behaviour

iHeater and iHeater-link can be powered up simultaneously. iHeater-link needs time to bring up Wi-Fi and connect to its command source, so for the first 20 seconds after boot the firmware does not treat the absence of frames as a fault and shows a slow chasing light (1000 ms step) — "waiting for the first frame".

If no valid frame is received during this 20-second window, the firmware enters ERROR_LINK_LOST exactly as it would after a runtime drop.

Once the first frame has been received, the normal rule applies: a gap of more than 1.5 seconds with no frames triggers the fault.

When the fault fires:

1. The firmware persists error code 0x08 (ERROR_LINK_LOST) in flash.
2. The MCU is reset.
3. After the reset the heater is off; the firmware again opens a 20-second waiting window with the slow chasing light, then falls back to the slow synchronous blink of all three LEDs.
4. To clear the error, hold the MODE button while powering the device on, then release it. The device returns to normal operation.

MODE button

In the pulse build, the MODE button does not cycle modes and does not trigger calibration. Its only purpose is clearing a persisted error at startup. All heating commands come from iHeater-link.

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How to Flash the Firmware

Download

Скачайте прошивку со страницы релизов

Using Precompiled Binary

Download the firmware from the releases page

This firmware is pre-configured with the temperature modes from MODE_TEMP_0 to MODE_TEMP_7 (as described above) and designed to work with a Generic 3950 thermistor (type 3 in config.h).

Using DFU Mode (USB)

r1r1.1

1. Set the BOOT0 jumper
2. Connect USB, the device will be recognized as DFU 3.1 Upload the firmware using STM32CubeProgrammer:

3.1.1 Specify the path to the .bin firmware file (e.g.: Firmware/iHeater_v1.2.3.bin) 3.1.2 Set the download address: 0x08000000

3.1.3 Click "Start Programming"

or

3.2 Upload the firmware via command line:

dfu-util -a 0 -s 0x08000000 -D Firmware/iHeater_vX.Y.Z.bin

1. Remove the jumper and power cycle the device

1. Press and hold the BOOT button
2. Connect USB, the device will be recognized as DFU

3. Upload the firmware using STM32CubeProgrammer:

   3.1.1 Specify the path to the .bin firmware file (e.g.: Firmware/iHeater_v1.2.3.bin)

   3.1.2 Set the download address: 0x08000000

   3.1.3 Click "Start Programming"

   or

   3.2 Upload the firmware via command line:

   dfu-util -a 0 -s 0x08000000 -D Firmware/iHeater_vX.Y.Z.bin
   

4. Power cycle the device

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How to Use

r1r1.1

• Short press of the MODE button - switches modes (0-7)
• Long press (2+ sec) - resets the mode to 0 (OFF)
• LED indicators display the current mode according to the table above
• Flashing LEDs - mode is active but target temperature not yet reached
• Solid light - target temperature reached

Revision Differences

revision r1.1 features a trigger port for automatic chamber heating control. When a thermistor is connected to the trigger port, heating will turn on and off according to the temperatures specified in config.h, by default 45 and 80 for heating activation and deactivation.

• Short press of the MODE button - switches modes (0-7)
• Long press (2+ sec) - resets the mode to 0 (OFF)
• LED indicators display the current mode according to the table above
• Flashing LEDs - mode is active but target temperature not yet reached
• Solid light - target temperature reached

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Error Handling

The device auto-resets and shows an error code using LED indicators. The fan will be switched on at the same time.

Code	Description	LED3	LED2	LED1
0x01	Air failed to reach target in time
0x02	Heater not responding
0x03	Manual shutdown (unused)
0x04	Air thermistor disconnected
0x05	Heater thermistor disconnected
0x06	Heater overtemperature
0x07	Air overtemperature
0x08	iHeater-link lost (pulse build only)	0.25 Hz	0.25 Hz	0.25 Hz
0xFF	Unknown error

Resetting an Error

Hold the MODE button during startup until the LEDs change. The stored error will be cleared from flash memory, and the device will resume normal operation.

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Fine Tuning

If there is confirmation that the thermistor readings deviate from the actual temperature, the fine tuning function can be used. For this purpose, it is necessary to measure the resistance of the corresponding resistors and record these values instead of the default ones.

Actual resistance of the pull-up resistors

#define PULLUP_TH0 4700.0f
#define PULLUP_TH1 4700.0f
#define PULLUP_TH2 4700.0f

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This software is licensed under the GNU General Public License v3.0 for non-commercial use only.