Initial commit: ESP32-C6 rack fan controller with ESPHome

3-zone PWM fan controller (intake/central/outtake) with DS18B20 temp
sensors, RPM monitoring, ST7789 LCD display, and Home Assistant
integration via ESPHome native API. USB-C PD powered.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

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+# ESPHome build artifacts
+esphome/.esphome/
+esphome/**/.pioenvs/
+esphome/**/.piolibdeps/
+
+# Secrets (never commit)
+esphome/secrets.yaml
+
+# IDE
+.vscode/
+.idea/
+
+# OS
+.DS_Store
+Thumbs.db

README.md

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+# Rack Fan Controller
+
+ESP32-C6 based smart rack/cabinet fan controller with temperature monitoring, automatic PWM fan speed control, and Home Assistant integration via ESPHome.
+
+## Features
+
+- **3-zone fan control**: Intake, Central, Outtake (2 fans per zone, 6 total)
+- **Temperature monitoring**: 3x DS18B20 sensors (one per zone)
+- **RPM monitoring**: Tachometer reading from one fan per zone
+- **Auto speed control**: Temperature-based PWM ramping with configurable thresholds
+- **Negative pressure**: Outtake fans run slightly faster for dust control
+- **1.47" LCD display**: Real-time temps, RPMs, and fan duty on Waveshare ST7789
+- **Home Assistant**: Full integration via ESPHome native API
+- **USB-C powered**: 65W PD charger -> ZY12PDN 12V trigger -> fans + ESP32
+
+## Hardware
+
+| Component | Qty | Notes |
+|-----------|-----|-------|
+| Waveshare ESP32-C6 LCD 1.47" | 1 | No-touch version, ST7789 172x320 |
+| Arctic P12 PWM 120mm | 6 | 4-pin, 2 per zone |
+| ZY12PDN USB-C PD trigger | 1 | Set to 12V output |
+| LM2596 buck converter | 1 | 12V -> 5V for ESP32 |
+| DS18B20 waterproof probe | 3 | 1m cable, 1-Wire bus |
+| PWM Y-splitter (4-pin) | 3 | 1-to-2 per zone |
+| KF301 screw terminals | 10 | PCB connections |
+| 4.7kOhm resistor | 1 | DS18B20 pull-up |
+| 5x7cm prototype PCB | 1 | Main board |
+
+## GPIO Mapping (Waveshare ESP32-C6 LCD 1.47")
+
+### LCD (occupied - do not use)
+| Function | GPIO |
+|----------|------|
+| LCD MOSI | 6 |
+| LCD CLK | 7 |
+| LCD CS | 14 |
+| LCD DC | 15 |
+| LCD RST | 21 |
+| LCD BLK | 22 |
+| RGB LED | 8 |
+| SD MISO | 5 |
+| SD CS | 4 |
+
+### Project Pin Assignment
+| Function | GPIO | Notes |
+|----------|------|-------|
+| PWM Intake | 0 | Zone 1 - via Y-splitter to 2 fans |
+| PWM Central | 1 | Zone 2 - via Y-splitter to 2 fans |
+| PWM Outtake | 2 | Zone 3 - via Y-splitter to 2 fans |
+| Tach Intake | 3 | RPM from 1 fan in zone 1 |
+| Tach Central | 10 | RPM from 1 fan in zone 2 |
+| Tach Outtake | 11 | RPM from 1 fan in zone 3 |
+| DS18B20 bus | 9 | All 3 sensors on single 1-Wire bus |
+
+## Wiring Diagram
+
+```
+USB-C PD Charger (65W+)
+    |
+    USB-C cable
+    |
+    v
+ZY12PDN (set to 12V) ----+------ 12V Rail
+    |                     |
+    v                     +--- Y-splitter --- Fan1 + Fan2 (INTAKE)
+LM2596 (out=5V)           |                   |
+    |                     +--- Y-splitter --- Fan3 + Fan4 (CENTRAL)
+    v                     |                   |
+ESP32-C6 (5V in)          +--- Y-splitter --- Fan5 + Fan6 (OUTTAKE)
+    |
+    +-- GPIO0 (PWM) ----> Intake splitter PWM pin
+    +-- GPIO1 (PWM) ----> Central splitter PWM pin
+    +-- GPIO2 (PWM) ----> Outtake splitter PWM pin
+    |
+    +-- GPIO3 (TACH) <--- Fan1 tach (yellow wire)
+    +-- GPIO10 (TACH) <-- Fan3 tach (yellow wire)
+    +-- GPIO11 (TACH) <-- Fan5 tach (yellow wire)
+    |
+    +-- GPIO9 (1-Wire) --+-- DS18B20 (intake)
+                          +-- DS18B20 (central)
+                          +-- DS18B20 (outtake)
+                          |
+                         4.7k pull-up to 3.3V
+```
+
+### 4-Pin Fan Connector Pinout
+```
+Pin 1 (Black)  = GND
+Pin 2 (Yellow) = +12V
+Pin 3 (Green)  = Tach (RPM signal)
+Pin 4 (Blue)   = PWM control
+```
+
+## Temperature Control Logic
+
+| Temp Range | Intake | Central | Outtake | Notes |
+|------------|--------|---------|---------|-------|
+| < 28C | 20% | 20% | 25% | Near-silent baseline |
+| 28-35C | 20-50% | 20-50% | 25-55% | Gentle ramp |
+| 35-42C | 50-80% | 50-80% | 55-85% | Medium cooling |
+| 42-50C | 80-100% | 80-100% | 85-100% | Full cooling |
+| > 50C | 100% | 100% | 100% | Emergency + HA alert |
+
+Outtake always runs +5% over intake for slight negative pressure (dust control).
+
+## Build & Flash
+
+```bash
+# Install ESPHome
+pip install esphome
+
+# Validate config
+esphome config esphome/rack-fan-controller.yaml
+
+# Flash (first time via USB)
+esphome run esphome/rack-fan-controller.yaml
+
+# Subsequent updates via OTA
+esphome run esphome/rack-fan-controller.yaml --device rack-fan-ctrl.local
+```
+
+## Home Assistant
+
+After flashing, the device auto-discovers in HA via ESPHome integration. Exposed entities:
+
+- `sensor.rack_temp_intake` / `central` / `outtake`
+- `sensor.rack_fan_rpm_intake` / `central` / `outtake`
+- `sensor.rack_fan_duty_intake` / `central` / `outtake`
+- `switch.rack_fan_auto_mode` (enable/disable auto control)
+- `number.rack_fan_target_temp` (target temperature setpoint)
+- `number.rack_fan_min_duty` / `max_duty` (manual override range)
+
+## License
+
+MIT

esphome/rack-fan-controller.yaml

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+substitutions:
+  device_name: rack-fan-ctrl
+  friendly_name: "Rack Fan Controller"
+
+  # Temperature thresholds (Celsius)
+  temp_min: "28.0"    # Below this: minimum fan speed
+  temp_low: "35.0"    # Ramp midpoint
+  temp_high: "42.0"   # Ramp to max
+  temp_crit: "50.0"   # Emergency: 100% + alert
+
+  # Fan duty limits (0.0 - 1.0)
+  fan_min_duty: "0.20"
+  fan_max_duty: "1.0"
+
+  # Outtake offset (extra duty for negative pressure)
+  outtake_offset: "0.05"
+
+  # GPIO assignments - Waveshare ESP32-C6 LCD 1.47"
+  pin_pwm_intake: GPIO0
+  pin_pwm_central: GPIO1
+  pin_pwm_outtake: GPIO2
+  pin_tach_intake: GPIO3
+  pin_tach_central: GPIO10
+  pin_tach_outtake: GPIO11
+  pin_onewire: GPIO9
+
+  # LCD pins (Waveshare ESP32-C6 LCD 1.47" defaults)
+  pin_lcd_mosi: GPIO6
+  pin_lcd_clk: GPIO7
+  pin_lcd_cs: GPIO14
+  pin_lcd_dc: GPIO15
+  pin_lcd_rst: GPIO21
+  pin_lcd_bl: GPIO22
+
+esphome:
+  name: ${device_name}
+  friendly_name: ${friendly_name}
+  on_boot:
+    priority: -100
+    then:
+      - output.set_level:
+          id: lcd_backlight
+          level: 80%
+      - switch.turn_on: auto_mode
+
+esp32:
+  board: esp32-c6-devkitc-1
+  framework:
+    type: esp-idf
+
+logger:
+  level: INFO
+
+api:
+  encryption:
+    key: !secret api_encryption_key
+
+ota:
+  - platform: esphome
+    password: !secret ota_password
+
+wifi:
+  ssid: !secret wifi_ssid
+  password: !secret wifi_password
+  ap:
+    ssid: "${device_name}-fallback"
+    password: "rackfan123"
+
+captive_portal:
+
+# --- SPI bus (shared by LCD) ---
+spi:
+  clk_pin: ${pin_lcd_clk}
+  mosi_pin: ${pin_lcd_mosi}
+
+# --- LCD Backlight ---
+output:
+  - platform: ledc
+    pin: ${pin_lcd_bl}
+    id: lcd_backlight
+    frequency: 1000Hz
+
+  # --- Fan PWM outputs (25kHz per Intel 4-pin spec) ---
+  - platform: ledc
+    pin: ${pin_pwm_intake}
+    id: pwm_intake
+    frequency: 25000Hz
+
+  - platform: ledc
+    pin: ${pin_pwm_central}
+    id: pwm_central
+    frequency: 25000Hz
+
+  - platform: ledc
+    pin: ${pin_pwm_outtake}
+    id: pwm_outtake
+    frequency: 25000Hz
+
+# --- 1-Wire bus for DS18B20 sensors ---
+one_wire:
+  - platform: gpio
+    pin: ${pin_onewire}
+
+# --- Temperature sensors ---
+sensor:
+  # DS18B20 sensors - addresses auto-discovered on first boot
+  # After first boot, check logs for addresses and pin them here
+  - platform: dallas_temp
+    name: "Rack Temp Intake"
+    id: temp_intake
+    update_interval: 5s
+    filters:
+      - sliding_window_moving_average:
+          window_size: 3
+          send_every: 1
+
+  - platform: dallas_temp
+    name: "Rack Temp Central"
+    id: temp_central
+    update_interval: 5s
+    filters:
+      - sliding_window_moving_average:
+          window_size: 3
+          send_every: 1
+
+  - platform: dallas_temp
+    name: "Rack Temp Outtake"
+    id: temp_outtake
+    update_interval: 5s
+    filters:
+      - sliding_window_moving_average:
+          window_size: 3
+          send_every: 1
+
+  # Fan tachometer (RPM) - 2 pulses per revolution
+  - platform: pulse_counter
+    pin:
+      number: ${pin_tach_intake}
+      mode:
+        input: true
+        pullup: true
+    name: "Rack Fan RPM Intake"
+    id: rpm_intake
+    update_interval: 5s
+    count_mode:
+      rising_edge: INCREMENT
+      falling_edge: DISABLE
+    filters:
+      - multiply: 0.5  # 2 pulses per rev -> divide by 2
+      - multiply: 12   # per-5s count * 12 = per-minute
+
+  - platform: pulse_counter
+    pin:
+      number: ${pin_tach_central}
+      mode:
+        input: true
+        pullup: true
+    name: "Rack Fan RPM Central"
+    id: rpm_central
+    update_interval: 5s
+    count_mode:
+      rising_edge: INCREMENT
+      falling_edge: DISABLE
+    filters:
+      - multiply: 0.5
+      - multiply: 12
+
+  - platform: pulse_counter
+    pin:
+      number: ${pin_tach_outtake}
+      mode:
+        input: true
+        pullup: true
+    name: "Rack Fan RPM Outtake"
+    id: rpm_outtake
+    update_interval: 5s
+    count_mode:
+      rising_edge: INCREMENT
+      falling_edge: DISABLE
+    filters:
+      - multiply: 0.5
+      - multiply: 12
+
+  # Computed fan duty percentages (for display and HA)
+  - platform: template
+    name: "Rack Fan Duty Intake"
+    id: duty_intake
+    unit_of_measurement: "%"
+    accuracy_decimals: 0
+    update_interval: 5s
+
+  - platform: template
+    name: "Rack Fan Duty Central"
+    id: duty_central
+    unit_of_measurement: "%"
+    accuracy_decimals: 0
+    update_interval: 5s
+
+  - platform: template
+    name: "Rack Fan Duty Outtake"
+    id: duty_outtake
+    unit_of_measurement: "%"
+    accuracy_decimals: 0
+    update_interval: 5s
+
+  # WiFi signal for diagnostics
+  - platform: wifi_signal
+    name: "Rack Controller WiFi"
+    update_interval: 60s
+
+# --- Auto/Manual mode switch ---
+switch:
+  - platform: template
+    name: "Rack Fan Auto Mode"
+    id: auto_mode
+    optimistic: true
+    restore_mode: RESTORE_DEFAULT_ON
+
+# --- Configurable setpoints from HA ---
+number:
+  - platform: template
+    name: "Rack Target Temp"
+    id: target_temp
+    min_value: 20
+    max_value: 50
+    step: 1
+    initial_value: 35
+    optimistic: true
+    unit_of_measurement: "C"
+    restore_value: true
+
+  - platform: template
+    name: "Rack Fan Min Duty"
+    id: min_duty
+    min_value: 0
+    max_value: 100
+    step: 5
+    initial_value: 20
+    optimistic: true
+    unit_of_measurement: "%"
+    restore_value: true
+
+  - platform: template
+    name: "Rack Fan Max Duty"
+    id: max_duty
+    min_value: 20
+    max_value: 100
+    step: 5
+    initial_value: 100
+    optimistic: true
+    unit_of_measurement: "%"
+    restore_value: true
+
+# --- Binary sensor for overheat alert ---
+binary_sensor:
+  - platform: template
+    name: "Rack Overheat Alert"
+    id: overheat_alert
+    device_class: heat
+    lambda: |-
+      if (!id(temp_central).has_state()) return false;
+      return id(temp_central).state >= ${temp_crit};
+
+# --- Fan control automation ---
+interval:
+  - interval: 5s
+    then:
+      - lambda: |-
+          if (!id(auto_mode).state) return;
+
+          // Get max temperature from all sensors (use central as primary)
+          float temp = 0;
+          int count = 0;
+          if (id(temp_intake).has_state()) { temp += id(temp_intake).state; count++; }
+          if (id(temp_central).has_state()) { temp += id(temp_central).state; count++; }
+          if (id(temp_outtake).has_state()) { temp += id(temp_outtake).state; count++; }
+
+          // Use central temp if available, otherwise average
+          if (id(temp_central).has_state()) {
+            temp = id(temp_central).state;
+          } else if (count > 0) {
+            temp = temp / count;
+          } else {
+            // No sensors reporting - run at 50% as safety
+            auto call_i = id(pwm_intake).make_call();
+            call_i.set_level(0.5);
+            call_i.perform();
+            auto call_c = id(pwm_central).make_call();
+            call_c.set_level(0.5);
+            call_c.perform();
+            auto call_o = id(pwm_outtake).make_call();
+            call_o.set_level(0.55);
+            call_o.perform();
+            return;
+          }
+
+          // Get configurable limits
+          float d_min = id(min_duty).state / 100.0;
+          float d_max = id(max_duty).state / 100.0;
+          float t_target = id(target_temp).state;
+
+          // Calculate duty: linear ramp from min to max
+          // Ramp starts 7C below target, reaches max at 8C above target
+          float t_start = t_target - 7.0;
+          float t_end = t_target + 8.0;
+          float duty = 0;
+
+          if (temp <= t_start) {
+            duty = d_min;
+          } else if (temp >= t_end) {
+            duty = d_max;
+          } else {
+            duty = d_min + (d_max - d_min) * (temp - t_start) / (t_end - t_start);
+          }
+
+          // Clamp
+          if (duty < d_min) duty = d_min;
+          if (duty > 1.0) duty = 1.0;
+
+          // Outtake runs slightly faster for negative pressure
+          float outtake_duty = duty + ${outtake_offset};
+          if (outtake_duty > 1.0) outtake_duty = 1.0;
+
+          // Apply PWM
+          auto call_i = id(pwm_intake).make_call();
+          call_i.set_level(duty);
+          call_i.perform();
+
+          auto call_c = id(pwm_central).make_call();
+          call_c.set_level(duty);
+          call_c.perform();
+
+          auto call_o = id(pwm_outtake).make_call();
+          call_o.set_level(outtake_duty);
+          call_o.perform();
+
+          // Update duty sensors for HA / display
+          id(duty_intake).publish_state(duty * 100.0);
+          id(duty_central).publish_state(duty * 100.0);
+          id(duty_outtake).publish_state(outtake_duty * 100.0);
+
+# --- Display (Waveshare ESP32-C6 1.47" ST7789 172x320) ---
+font:
+  - file: "gfonts://Roboto"
+    id: font_title
+    size: 18
+    glyphs: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 .:%/-"
+
+  - file: "gfonts://Roboto"
+    id: font_value
+    size: 28
+    glyphs: "0123456789.C%RPM "
+
+  - file: "gfonts://Roboto"
+    id: font_label
+    size: 14
+    glyphs: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 .:%/-"
+
+  - file: "gfonts://Roboto"
+    id: font_small
+    size: 11
+    glyphs: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 .:%/-"
+
+color:
+  - id: color_white
+    white: 100%
+  - id: color_bg
+    red: 10%
+    green: 10%
+    blue: 15%
+  - id: color_blue
+    red: 30%
+    green: 60%
+    blue: 100%
+  - id: color_cyan
+    red: 0%
+    green: 90%
+    blue: 90%
+  - id: color_green
+    red: 20%
+    green: 90%
+    blue: 20%
+  - id: color_yellow
+    red: 100%
+    green: 90%
+    blue: 0%
+  - id: color_orange
+    red: 100%
+    green: 60%
+    blue: 0%
+  - id: color_red
+    red: 100%
+    green: 20%
+    blue: 20%
+  - id: color_gray
+    red: 50%
+    green: 50%
+    blue: 50%
+
+display:
+  - platform: st7789v
+    id: lcd
+    cs_pin: ${pin_lcd_cs}
+    dc_pin: ${pin_lcd_dc}
+    reset_pin: ${pin_lcd_rst}
+    model: Custom
+    width: 172
+    height: 320
+    offset_height: 34
+    offset_width: 0
+    eightbitcolor: false
+    update_interval: 2s
+    rotation: 0
+    lambda: |-
+      // Background
+      it.fill(id(color_bg));
+
+      // Title bar
+      it.filled_rectangle(0, 0, 172, 24, id(color_blue));
+      it.printf(86, 3, id(font_title), id(color_white), TextAlign::TOP_CENTER, "RACK FANS");
+
+      // Helper: pick color based on temperature
+      auto temp_color = [&](float t) -> Color {
+        if (t < 28) return id(color_green);
+        if (t < 35) return id(color_cyan);
+        if (t < 42) return id(color_yellow);
+        if (t < 50) return id(color_orange);
+        return id(color_red);
+      };
+
+      // Helper: pick color based on duty
+      auto duty_color = [&](float d) -> Color {
+        if (d < 30) return id(color_green);
+        if (d < 60) return id(color_cyan);
+        if (d < 80) return id(color_yellow);
+        return id(color_orange);
+      };
+
+      int y = 30;
+      int section_h = 90;
+
+      // --- INTAKE ZONE ---
+      it.printf(6, y, id(font_label), id(color_blue), "INTAKE");
+      y += 16;
+      if (id(temp_intake).has_state()) {
+        float t = id(temp_intake).state;
+        it.printf(6, y, id(font_value), temp_color(t), "%.1fC", t);
+      } else {
+        it.printf(6, y, id(font_value), id(color_gray), "--.-C");
+      }
+      y += 30;
+      if (id(rpm_intake).has_state()) {
+        it.printf(6, y, id(font_label), id(color_white), "%.0f RPM", id(rpm_intake).state);
+      }
+      if (id(duty_intake).has_state()) {
+        it.printf(166, y, id(font_label), duty_color(id(duty_intake).state), TextAlign::TOP_RIGHT, "%.0f%%", id(duty_intake).state);
+      }
+      y += 18;
+
+      // Separator
+      it.horizontal_line(10, y, 152, id(color_gray));
+      y += 6;
+
+      // --- CENTRAL ZONE ---
+      it.printf(6, y, id(font_label), id(color_blue), "CENTRAL");
+      y += 16;
+      if (id(temp_central).has_state()) {
+        float t = id(temp_central).state;
+        it.printf(6, y, id(font_value), temp_color(t), "%.1fC", t);
+      } else {
+        it.printf(6, y, id(font_value), id(color_gray), "--.-C");
+      }
+      y += 30;
+      if (id(rpm_central).has_state()) {
+        it.printf(6, y, id(font_label), id(color_white), "%.0f RPM", id(rpm_central).state);
+      }
+      if (id(duty_central).has_state()) {
+        it.printf(166, y, id(font_label), duty_color(id(duty_central).state), TextAlign::TOP_RIGHT, "%.0f%%", id(duty_central).state);
+      }
+      y += 18;
+
+      // Separator
+      it.horizontal_line(10, y, 152, id(color_gray));
+      y += 6;
+
+      // --- OUTTAKE ZONE ---
+      it.printf(6, y, id(font_label), id(color_blue), "OUTTAKE");
+      y += 16;
+      if (id(temp_outtake).has_state()) {
+        float t = id(temp_outtake).state;
+        it.printf(6, y, id(font_value), temp_color(t), "%.1fC", t);
+      } else {
+        it.printf(6, y, id(font_value), id(color_gray), "--.-C");
+      }
+      y += 30;
+      if (id(rpm_outtake).has_state()) {
+        it.printf(6, y, id(font_label), id(color_white), "%.0f RPM", id(rpm_outtake).state);
+      }
+      if (id(duty_outtake).has_state()) {
+        it.printf(166, y, id(font_label), duty_color(id(duty_outtake).state), TextAlign::TOP_RIGHT, "%.0f%%", id(duty_outtake).state);
+      }
+      y += 22;
+
+      // --- STATUS BAR ---
+      it.horizontal_line(0, y, 172, id(color_blue));
+      y += 4;
+
+      // Auto/Manual mode indicator
+      if (id(auto_mode).state) {
+        it.printf(6, y, id(font_small), id(color_green), "AUTO");
+      } else {
+        it.printf(6, y, id(font_small), id(color_yellow), "MANUAL");
+      }
+
+      // WiFi indicator
+      if (WiFi.isConnected()) {
+        it.printf(166, y, id(font_small), id(color_green), TextAlign::TOP_RIGHT, "WiFi OK");
+      } else {
+        it.printf(166, y, id(font_small), id(color_red), TextAlign::TOP_RIGHT, "NO WiFi");
+      }
+
+      // Overheat warning
+      if (id(overheat_alert).state) {
+        it.filled_rectangle(30, 140, 112, 30, id(color_red));
+        it.printf(86, 143, id(font_title), id(color_white), TextAlign::TOP_CENTER, "OVERHEAT!");
+      }

esphome/secrets.yaml.example

@@ -0,0 +1,5 @@
+# Copy to secrets.yaml and fill in your values
+wifi_ssid: "YourWiFiSSID"
+wifi_password: "YourWiFiPassword"
+api_encryption_key: "generate-with-esphome"
+ota_password: "your-ota-password"

esphome/simulation.yaml

@@ -0,0 +1,51 @@
+# Simulation overlay for testing without physical hardware
+# Usage: esphome run rack-fan-controller.yaml
+# Then use HA developer tools to set simulated sensor values
+#
+# This file documents how to test the controller logic
+# without real DS18B20 sensors or fans connected.
+#
+# Method 1: ESPHome dashboard
+#   - Flash the normal config to any ESP32-C6
+#   - The sensors will show "unknown" but the control loop
+#     handles missing sensors gracefully (defaults to 50% duty)
+#   - Use HA number entities to adjust target temp and duty limits
+#
+# Method 2: Home Assistant template sensors
+#   Add these to your HA configuration.yaml to simulate temps:
+#
+#   input_number:
+#     sim_rack_temp_intake:
+#       name: "Sim Rack Temp Intake"
+#       min: 15
+#       max: 70
+#       step: 0.5
+#       initial: 25
+#       unit_of_measurement: "C"
+#     sim_rack_temp_central:
+#       name: "Sim Rack Temp Central"
+#       min: 15
+#       max: 70
+#       step: 0.5
+#       initial: 30
+#       unit_of_measurement: "C"
+#     sim_rack_temp_outtake:
+#       name: "Sim Rack Temp Outtake"
+#       min: 15
+#       max: 70
+#       step: 0.5
+#       initial: 27
+#       unit_of_measurement: "C"
+#
+# Method 3: Test the display layout
+#   Flash to the real Waveshare ESP32-C6 board (even without
+#   sensors/fans connected). The display will render with
+#   "--.-C" placeholders and you can verify the layout.
+#
+# Expected behavior matrix:
+#   temp < 28C  -> duty = min_duty (default 20%)
+#   temp = 35C  -> duty ~= 50% (midpoint of default ramp)
+#   temp = 42C  -> duty ~= 80%
+#   temp > 43C  -> duty = max_duty (default 100%)
+#   temp > 50C  -> overheat alert triggers
+#   no sensors  -> duty = 50% (safety fallback)