Reheat A0
From iagent
Reheat is a 6 output heater board with temperature sensors and fans for multi material printing.
Schematics
Config tool
pin description
This is temporary while waiting for a proper pinout
Features
- RP2354B microcontroller (ARM Cortex-M33, 150 MHz)
- 6x heater outputs (24 V, MOSFET-switched)
- 6x fan outputs (24 V PWM) with tachometer inputs
- 6x thermistor/temperature sensor inputs
- Supports: NTC 10K, NTC 100K, PT100, PT1000, Type K thermocouple
- Jumper-selectable per channel
- 12x endstop inputs (5 V tolerant, TVS-protected)
- ENDSTOP-12 supports a bidirectional signal (e.g. filament encoder)
- USB-C interface (USB 2.0)
- 24 V power input with onboard 5 V (3 A) and 3.3 V regulation
- Overcurrent detection on fan bus
Pinout
| GPIO | Signal | Connector |
|---|---|---|
| GPIO0 | HEATER-1 | J2 |
| GPIO1 | HEATER-2 | J3 |
| GPIO2 | HEATER-3 | J6 |
| GPIO3 | HEATER-4 | J11 |
| GPIO4 | HEATER-5 | J12 |
| GPIO5 | HEATER-6 | J13 |
| GPIO6 | FAN-1 | J34 |
| GPIO7 | FAN-2 | J35 |
| GPIO8 | FAN-3 | J36 |
| GPIO9 | FAN-4 | J37 |
| GPIO10 | FAN-5 | J38 |
| GPIO11 | FAN-6 | J39 |
| GPIO12 | TACH-1 | J34 |
| GPIO13 | TACH-2 | J35 |
| GPIO14 | TACH-3 | J36 |
| GPIO15 | TACH-4 | J37 |
| GPIO16 | TACH-5 | J38 |
| GPIO17 | TACH-6 | J39 |
| GPIO18 | ENDSTOP-1 | J14 |
| GPIO19 | ENDSTOP-2 | J15 |
| GPIO20 | ENDSTOP-3 | J16 |
| GPIO21 | ENDSTOP-4 | J17 |
| GPIO22 | ENDSTOP-5 | J18 |
| GPIO23 | ENDSTOP-6 | J19 |
| GPIO24 | ENDSTOP-7 | J20 |
| GPIO25 | ENDSTOP-8 | J21 |
| GPIO26 | ENDSTOP-9 | J22 |
| GPIO27 | ENDSTOP-10 | J23 |
| GPIO28 | ENDSTOP-11 | J24 |
| GPIO29 | ENDSTOP-12 | J25 |
| GPIO30 | MUX-S0 | Internal |
| GPIO31 | MUX-S1 | Internal |
| GPIO32 | MUX-S2 | Internal |
| GPIO33 | PWM-GAIN | Internal |
| GPIO34 | PWM-OFFSET | Internal |
| GPIO35 | PWM-CURRENT | Internal |
| GPIO36 | EN-PULLUP | Internal |
| GPIO37 | ENDSTOP-12-DIR | J25 |
| GPIO38 | FAN-OC (overcurrent) | Internal |
| GPIO40 / ADC0 | THERM-1 | J27 |
| GPIO41 / ADC1 | THERM-2 | J28 |
| GPIO42 / ADC2 | THERM-3 | J29 |
| GPIO43 / ADC3 | THERM-4 | J30 |
| GPIO44 / ADC4 | THERM-5 | J31 |
| GPIO45 / ADC5 | THERM-6 | J32 |
| GPIO46 / ADC6 | ADC (MUX output) | Internal |
| GPIO47 / ADC7 | CURRENT sense | Internal |
Hardware connections
Power
The board takes 24 V DC on a 4-pin connector (J33). A fuse (F1) and a 2 mΩ current-sense resistor (R98) protect the input. Onboard regulators provide +5 V (TPS54302 buck converter, 3 A) and +3.3 V (AMS1117-3.3, 1 A) for logic and sensor pull-ups.
Heaters
Six heater outputs use 2SK3019 N-channel MOSFETs driven from GPIO0–GPIO5. Each output has a 2-pin female connector and a flyback Schottky diode. The heater voltage is 24 V.
Fans
Six fan outputs (GPIO6–GPIO11) use N-channel MOSFETs with a 24 V supply. Each has a 3-pin connector (V+, GND, TACH). Tachometer signals are read on GPIO12–GPIO17. An LM393 comparator monitors the fan bus for overcurrent and signals FAN-OC on GPIO38.
Thermistors
Each thermistor channel has a 3-pin connector (J27–J32) with a jumper (JP1–JP6) to select the measurement mode. An analog MUX (CD4051) and op-amp signal conditioning chain feed the ADC inputs (GPIO40–GPIO45). The signal conditioning supports:
| Sensor type | Measurement method |
|---|---|
| NTC 10K | Voltage divider with 4.7 K pull-up |
| NTC 100K | Voltage divider with 4.7 K pull-up |
| PT100 | 1 mA constant current source (Kelvin connection) |
| PT1000 | 1 mA constant current source (Kelvin connection) |
| Type K thermocouple | ×101 gain amplifier, buffered |
For NTC thermistor or PT1000 measurements, close jumpers JP1–JP6 to connect the 4.7 K pull-up resistors. With the jumpers closed, ADC0–ADC5 (GPIO40–GPIO45) can be used as standard thermistor inputs with a 4.7 K pull-up to 3.3 V, without the need for any additional signal conditioning.
Errata
- DP/DM USB data lines are swapped.
- RUN pin is hardwired to ground, preventing software reset.
- U11 and U15 (LMV321 op-amps in thermistor circuit) have V+ and V- supply pins reversed.
- Pull-up resistor footprints (JP1–JP6) use a 1 mm pin pitch instead of the standard 2.54 mm.
- VUSB is unconnected, so the board requires 24 V power to operate even when connected over USB.
Klipper configuration
The Reheat A0 connects to the host over USB and is configured as an MCU in Klipper. Find the serial path with ls /dev/serial/by-id/ and add to printer.cfg:
[mcu reheat] serial: /dev/serial/by-id/usb-Klipper_rp2350_XXXXXXXXXXXX-if00
Heaters
[heater_generic heater1] heater_pin: reheat:gpio0 sensor_type: NTC 100K MGB18-104F39050L32 sensor_pin: reheat:gpio40 control: pid pid_Kp: 22 pid_Ki: 1.08 pid_Kd: 114 [heater_generic heater2] heater_pin: reheat:gpio1 sensor_type: NTC 100K MGB18-104F39050L32 sensor_pin: reheat:gpio41 control: pid pid_Kp: 22 pid_Ki: 1.08 pid_Kd: 114
Fans
[fan_generic fan1] pin: reheat:gpio6 [fan_generic fan2] pin: reheat:gpio7
Endstops
Endstop pins can be referenced in the relevant stepper sections:
[stepper_x] endstop_pin: reheat:gpio18
Flashing Klipper
- Put the board in BOOTSEL mode: hold the BOOT button while plugging in USB (or hold BOOT, press RESET, then release BOOT).
- Build and flash from the Klipper source directory:
make menuconfig # Processor model: rp2350 # Bootloader offset: No bootloader # Communication interface: USBSERIAL make picotool load out/klipper.uf2 --force picotool reboot
The board will reboot and appear as /dev/ttyACM0 (or similar).
Full config file
# ====================================================================== # Reheat_A0.cfg — Complete Klipper configuration for the Reheat A0 # MCU: RP2354B (RP2350 family, ARM Cortex-M33, 150 MHz, 48 GPIO, 8 ADC) # Source: https://wiki.iagent.no/wiki/Reheat_A0 # # Board functions: # 6x heater outputs (24V MOSFET) GPIO0..GPIO5 # 6x fan outputs (24V PWM) GPIO6..GPIO11 # 6x fan tachometer inputs GPIO12..GPIO17 # 12x endstop inputs (5V tolerant) GPIO18..GPIO29 (+ GPIO37 dir) # 6x thermistor/temperature ADC inputs GPIO40..GPIO45 (ADC0..ADC5) # analog mux + PWM bias control GPIO30..GPIO35 # endstop pull-up enable GPIO36 # fan over-current flag GPIO38 # ADC mux output / input-current sense GPIO46/GPIO47 (ADC6/ADC7) # # Each fan is paired with its matching heater (FAN1<->HEATER1, ...). # # Build firmware: RP2350 (ARM) processor, USB communication. # Flash: hold BOOT while plugging in USB-C to enter BOOTSEL. # ERRATA: RUN pin is hardwired -> Klipper cannot software-reset the MCU # (re-enter BOOTSEL manually to reflash). USB DP/DM are swapped. # ====================================================================== # ---------------------------------------------------------------------- # MCU # ---------------------------------------------------------------------- [mcu reheat] # USB-C, enumerates over USB. Use the stable by-id path: # ls /dev/serial/by-id/* serial: /dev/serial/by-id/usb-Klipper_rp2350_21745F8FD0431B3A-if00 restart_method: command # ---------------------------------------------------------------------- # Endstop pull-up enable (GPIO36) # Drive high at boot so the 12 endstop inputs read correctly. # ---------------------------------------------------------------------- [static_digital_output endstop_pullup_enable] pins: reheat:gpio36 # ====================================================================== # HEATERS (24V MOSFET outputs, paired with ADC thermistors) # Sensor types supported by the board: NTC 10K, NTC 100K, PT100, # PT1000, Type-K thermocouple. NTC 100K -> "Generic 3950". # Pairing of heater<->thermistor is arbitrary; reassign as needed. # ====================================================================== [heater_generic heater1] # HEATER1 / THERM1 heater_pin: reheat:gpio0 sensor_pin: reheat:gpio40 # ADC0 sensor_type: EPCOS 100K B57560G104F control: pid pid_Kp: 22 pid_Ki: 1.08 pid_Kd: 114 min_temp: -272 max_temp: 300 [heater_generic heater2] # HEATER2 / THERM2 heater_pin: reheat:gpio1 sensor_pin: reheat:gpio41 # ADC1 sensor_type: EPCOS 100K B57560G104F control: pid pid_Kp: 22 pid_Ki: 1.08 pid_Kd: 114 min_temp: -272 max_temp: 300 [heater_generic heater3] # HEATER3 / THERM3 heater_pin: reheat:gpio2 sensor_pin: reheat:gpio42 # ADC2 sensor_type: EPCOS 100K B57560G104F control: watermark min_temp: -272 max_temp: 300 [heater_generic heater4] # HEATER4 / THERM4 heater_pin: reheat:gpio3 sensor_pin: reheat:gpio43 # ADC3 sensor_type: EPCOS 100K B57560G104F control: watermark min_temp: -272 max_temp: 300 [heater_generic heater5] # HEATER5 / THERM5 heater_pin: reheat:gpio4 sensor_pin: reheat:gpio44 # ADC4 sensor_type: EPCOS 100K B57560G104F control: watermark min_temp: -272 max_temp: 300 [heater_generic heater6] # HEATER6 / THERM6 heater_pin: reheat:gpio5 sensor_pin: reheat:gpio45 # ADC5 sensor_type: EPCOS 100K B57560G104F control: watermark min_temp: -272 max_temp: 300 # ====================================================================== # FANS (24V PWM) # Each fan follows its matching heater (FAN1<->HEATER1, FAN2<->HEATER2, # ... FAN6<->HEATER6) and turns on when that heater is active. # ====================================================================== [heater_fan fan1] # FAN1 -> HEATER1 pin: reheat:gpio6 heater: heater1 heater_temp: 50.0 [heater_fan fan2] # FAN2 -> HEATER2 pin: reheat:gpio7 heater: heater2 heater_temp: 50.0 [heater_fan fan3] # FAN3 -> HEATER3 pin: reheat:gpio8 heater: heater3 heater_temp: 50.0 [heater_fan fan4] # FAN4 -> HEATER4 pin: reheat:gpio9 heater: heater4 heater_temp: 50.0 [heater_fan fan5] # FAN5 -> HEATER5 pin: reheat:gpio10 heater: heater5 heater_temp: 50.0 [heater_fan fan6] # FAN6 -> HEATER6 pin: reheat:gpio11 heater: heater6 heater_temp: 50.0 # ====================================================================== # ENDSTOPS (11 inputs, 5V tolerant) + NeoPixel on EP12 # This board has no stepper drivers, so endstops are exposed as # runtime-readable buttons. To use one as a homing endstop instead, # reference its pin from a stepper on your motion board, e.g.: # [stepper_x] # endstop_pin: reheat:gpio18 # Endstop 12 (GPIO29) is wired to a NeoPixel data line (see below). # ====================================================================== # Each endstop is exposed as a button so its state is queryable. The # press/release gcode is intentionally empty (just reads the input). [gcode_button endstop1] pin: reheat:gpio18 press_gcode: release_gcode: [gcode_button endstop2] pin: reheat:gpio19 press_gcode: release_gcode: [gcode_button endstop3] pin: reheat:gpio20 press_gcode: release_gcode: [gcode_button endstop4] pin: reheat:gpio21 press_gcode: release_gcode: [gcode_button endstop5] pin: reheat:gpio22 press_gcode: release_gcode: [gcode_button endstop6] pin: reheat:gpio23 press_gcode: release_gcode: [gcode_button endstop7] pin: reheat:gpio24 press_gcode: release_gcode: [gcode_button endstop8] pin: reheat:gpio25 press_gcode: release_gcode: [gcode_button endstop9] pin: reheat:gpio26 press_gcode: release_gcode: [gcode_button endstop10] pin: reheat:gpio27 press_gcode: release_gcode: [gcode_button endstop11] pin: reheat:gpio28 press_gcode: release_gcode: # NeoPixel on the EP12 connector (GPIO29 data line). [neopixel reheat_led] pin: reheat:gpio29 chain_count: 1 color_order: GRB initial_RED: 0.0 initial_GREEN: 0.0 initial_BLUE: 0.0 # EP12 direction line (GPIO37) — drive the level-shifter towards the # NeoPixel (output direction). [static_digital_output endstop12_dir] pins: reheat:gpio37 # ====================================================================== # ANALOG MUX + PWM BIAS (board-internal sensor front-end) # MUX_S0..S2 select one of the multiplexed analog channels, read back # on ADC_MUX (GPIO46/ADC6). PWM_GAIN/OFFSET/CURRENT set the analog # amplifier bias used for PT100/thermocouple measurement. # These are exposed as raw pins; exact scaling is board-specific. # ====================================================================== [output_pin mux_s0] pin: reheat:gpio30 [output_pin mux_s1] pin: reheat:gpio31 [output_pin mux_s2] pin: reheat:gpio32 [output_pin pwm_gain] pin: reheat:gpio33 pwm: True cycle_time: 0.001 value: 0 [output_pin pwm_offset] pin: reheat:gpio34 pwm: True cycle_time: 0.001 value: 0 [output_pin pwm_current] pin: reheat:gpio35 pwm: True cycle_time: 0.001 value: 0 # ====================================================================== # PROTECTION / MONITORING # ====================================================================== # Fan over-current flag (GPIO38) — reads active on an over-current event. [gcode_button fan_overcurrent] pin: reheat:gpio38 press_gcode: release_gcode: # Input-current sense (GPIO47 / ADC7) via the 2 mΩ shunt. # Scale: 1 A = 0.1 V -> 3.3 V full-scale = 33 A. The reported # "temperature" value is therefore the input current in amps. [adc_temperature reheat_current] temperature1: 0 voltage1: 0 temperature2: 33 voltage2: 3.3 [temperature_sensor input_current] adc_voltage: 3.3 sensor_pin: reheat:gpio47 sensor_type: reheat_current min_temp: -1 max_temp: 40
Errata
- DP/DM USB data lines are swapped.
- RUN pin is hardwired to ground, preventing software reset.
- U11 and U15 (LMV321 op-amps in thermistor circuit) have V+ and V- supply pins reversed.
- Pull-up resistor footprints (JP1–JP6) use a 1 mm pin pitch instead of the standard 2.54 mm.