Working Beta Version Update for README, including the blog-post

KiCad/0004-DenshaBekutoru_v0.2/0004-DenshaBekutoru_v0.2

@@ -0,0 +1,37 @@
+*
+
+.subckt 0004-DenshaBekutoru_v0.2
+
+
+.model __D1 D
+.model __D2 D
+J6 __J6
+J5 __J5
+D10 __D10
+R3 Net-_A1-Vcc_ Net-_D10-A_ 220
+R1 Net-_D2-A_ Net-_D1-K_ 1.8k
+U2 __U2
+D1 Net-_D1-A_ Net-_D1-K_ __D1
+U1 __U1
+C4 Net-_D3-K_ GND 4.7u
+C5 Net-_D3-K_ GND 100n
+D3 __D3
+RV1 __RV1
+D11 __D11
+R4 Net-_D11-A_ Net-_A1-Vcc_ 220
+J8 __J8
+R9 GND Net-_J8-Pin_1_ 10k
+R2 Net-_D1-A_ Net-_D2-K_ 1.8k
+J1 __J1
+D2 Net-_D2-A_ Net-_D2-K_ __D2
+A1 __A1
+R5 Net-_J3-Pin_2_ Net-_A1-PadD9_ 220
+J7 __J7
+J3 __J3
+J2 __J2
+J4 __J4
+R6 Net-_J3-Pin_3_ Net-_A1-PadD9_ 220
+R7 Net-_J3-Pin_4_ Net-_A1-D3_INT1_ 220
+R8 Net-_J3-Pin_5_ Net-_A1-D3_INT1_ 220
+
+.ends

KiCad/0004-DenshaBekutoru_v0.2/0004-DenshaBekutoru_v0.2.csv

@@ -0,0 +1,25 @@
+"Reference","Value","Datasheet","Footprint","Qty","DNP"
+"A1","Arduino_Pro_Mini_Socket_NoSPH_V2","https://docs.arduino.cc/retired/boards/arduino-pro-mini","arduino-library:Arduino_Pro_Mini_Socket_NoSPH_V2","1",""
+"C4","4.7µF","~","Capacitor_THT:CP_Axial_L10.0mm_D6.0mm_P15.00mm_Horizontal","1",""
+"C5","100nF","~","Capacitor_THT:C_Disc_D3.0mm_W1.6mm_P2.50mm","1",""
+"D1,D2","1N4148","https://assets.nexperia.com/documents/data-sheet/1N4148_1N4448.pdf","Diode_THT:D_DO-35_SOD27_P7.62mm_Horizontal","2",""
+"D3","1N5819","http://www.vishay.com/docs/88525/1n5817.pdf","Diode_THT:D_DO-41_SOD81_P10.16mm_Horizontal","1",""
+"D4","LED Green","~","LED_THT:LED_D3.0mm","1",""
+"D5","LED Yellow","~","LED_THT:LED_D3.0mm","1",""
+"D10","LED: HL_A.1","","LED_THT:LED_D5.0mm_Clear","1",""
+"D11","LED: HL_A.2","","LED_THT:LED_D5.0mm_Clear","1",""
+"D12","LED: HL_B.1","","LED_THT:LED_D5.0mm_Clear","1",""
+"D13","LED: HL_B.2","","LED_THT:LED_D5.0mm_Clear","1",""
+"J1","from Lego","~","Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical","1",""
+"J2","Headlight GND","~","Connector_PinSocket_2.54mm:PinSocket_1x04_P2.54mm_Vertical","1",""
+"J3","Headlight GND; A1,2/B1,2","~","Connector_PinSocket_2.54mm:PinSocket_1x05_P2.54mm_Vertical","1",""
+"J4","Headlight Test","~","Connector_PinHeader_2.54mm:PinHeader_1x05_P2.54mm_Horizontal","1",""
+"J5","I2C","~","Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical","1",""
+"J6","TX/RX","~","Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical","1",""
+"J7","Add. Lights","~","Connector_PinSocket_2.54mm:PinSocket_1x04_P2.54mm_Vertical","1",""
+"J8","LDR (~1MOhm) Option","~","Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical","1",""
+"R1,R2","1.5k","~","Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal","2",""
+"R3,R4,R5,R6,R7,R8","220","~","Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal","6",""
+"R9","10k","~","Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal","1",""
+"RV1","1MOhm","~","Potentiometer_THT:Potentiometer_Piher_PT-10-V10_Vertical","1",""
+"U1,U2","PC817","http://www.soselectronic.cz/a_info/resource/d/pc817.pdf","Package_DIP:DIP-4_W7.62mm","2",""

KiCad/0004-DenshaBekutoru_v0.2/0004-DenshaBekutoru_v0.2.kicad_prl

@@ -1,7 +1,7 @@
 {
   "board": {
     "active_layer": 0,
-    "active_layer_preset": "",
+    "active_layer_preset": "All Layers",
     "auto_track_width": true,
     "hidden_netclasses": [],
     "hidden_nets": [],

KiCad/0004-DenshaBekutoru_v0.2/0004-DenshaBekutoru_v0.2.kicad_pro

@@ -2,12 +2,224 @@
   "board": {
     "3dviewports": [],
     "design_settings": {
-      "defaults": {},
+      "defaults": {
-      "diff_pair_dimensions": [],
+        "apply_defaults_to_fp_fields": false,
-      "drc_exclusions": [],
+        "apply_defaults_to_fp_shapes": false,
-      "rules": {},
+        "apply_defaults_to_fp_text": false,
-      "track_widths": [],
+        "board_outline_line_width": 0.05,
-      "via_dimensions": []
+        "copper_line_width": 0.2,
+        "copper_text_italic": false,
+        "copper_text_size_h": 1.5,
+        "copper_text_size_v": 1.5,
+        "copper_text_thickness": 0.3,
+        "copper_text_upright": false,
+        "courtyard_line_width": 0.05,
+        "dimension_precision": 4,
+        "dimension_units": 3,
+        "dimensions": {
+          "arrow_length": 1270000,
+          "extension_offset": 500000,
+          "keep_text_aligned": true,
+          "suppress_zeroes": false,
+          "text_position": 0,
+          "units_format": 1
+        },
+        "fab_line_width": 0.1,
+        "fab_text_italic": false,
+        "fab_text_size_h": 1.0,
+        "fab_text_size_v": 1.0,
+        "fab_text_thickness": 0.15,
+        "fab_text_upright": false,
+        "other_line_width": 0.1,
+        "other_text_italic": false,
+        "other_text_size_h": 1.0,
+        "other_text_size_v": 1.0,
+        "other_text_thickness": 0.15,
+        "other_text_upright": false,
+        "pads": {
+          "drill": 0.762,
+          "height": 1.524,
+          "width": 1.524
+        },
+        "silk_line_width": 0.1,
+        "silk_text_italic": false,
+        "silk_text_size_h": 1.0,
+        "silk_text_size_v": 1.0,
+        "silk_text_thickness": 0.1,
+        "silk_text_upright": false,
+        "zones": {
+          "min_clearance": 0.5
+        }
+      },
+      "diff_pair_dimensions": [
+        {
+          "gap": 0.0,
+          "via_gap": 0.0,
+          "width": 0.0
+        }
+      ],
+      "drc_exclusions": [
+        "courtyards_overlap|116847500|113255000|4b518c68-cacc-4ba0-bdd7-4ed203d87dd8|c5b5c5e2-5bf5-406f-bc2c-791c87e4bd5a",
+        "courtyards_overlap|116847500|116747500|4b518c68-cacc-4ba0-bdd7-4ed203d87dd8|ce87971b-d681-44d7-9fb7-23a15933148a",
+        "courtyards_overlap|126372500|116747500|1094a2e1-479d-4870-8b87-1411fc6da792|4b518c68-cacc-4ba0-bdd7-4ed203d87dd8",
+        "courtyards_overlap|130322874|113255000|4b518c68-cacc-4ba0-bdd7-4ed203d87dd8|ee659d06-72c1-451a-8938-35a721a086e2"
+      ],
+      "meta": {
+        "version": 2
+      },
+      "rule_severities": {
+        "annular_width": "error",
+        "clearance": "error",
+        "connection_width": "warning",
+        "copper_edge_clearance": "error",
+        "copper_sliver": "warning",
+        "courtyards_overlap": "error",
+        "diff_pair_gap_out_of_range": "error",
+        "diff_pair_uncoupled_length_too_long": "error",
+        "drill_out_of_range": "error",
+        "duplicate_footprints": "warning",
+        "extra_footprint": "warning",
+        "footprint": "error",
+        "footprint_symbol_mismatch": "warning",
+        "footprint_type_mismatch": "ignore",
+        "hole_clearance": "error",
+        "hole_near_hole": "error",
+        "holes_co_located": "warning",
+        "invalid_outline": "error",
+        "isolated_copper": "warning",
+        "item_on_disabled_layer": "error",
+        "items_not_allowed": "error",
+        "length_out_of_range": "error",
+        "lib_footprint_issues": "warning",
+        "lib_footprint_mismatch": "warning",
+        "malformed_courtyard": "error",
+        "microvia_drill_out_of_range": "error",
+        "missing_courtyard": "ignore",
+        "missing_footprint": "warning",
+        "net_conflict": "warning",
+        "npth_inside_courtyard": "ignore",
+        "padstack": "warning",
+        "pth_inside_courtyard": "ignore",
+        "shorting_items": "error",
+        "silk_edge_clearance": "ignore",
+        "silk_over_copper": "warning",
+        "silk_overlap": "warning",
+        "skew_out_of_range": "error",
+        "solder_mask_bridge": "error",
+        "starved_thermal": "error",
+        "text_height": "warning",
+        "text_thickness": "warning",
+        "through_hole_pad_without_hole": "error",
+        "too_many_vias": "error",
+        "track_dangling": "warning",
+        "track_width": "error",
+        "tracks_crossing": "error",
+        "unconnected_items": "error",
+        "unresolved_variable": "error",
+        "via_dangling": "warning",
+        "zones_intersect": "error"
+      },
+      "rules": {
+        "max_error": 0.005,
+        "min_clearance": 0.0,
+        "min_connection": 0.0,
+        "min_copper_edge_clearance": 0.5,
+        "min_hole_clearance": 0.25,
+        "min_hole_to_hole": 0.25,
+        "min_microvia_diameter": 0.2,
+        "min_microvia_drill": 0.1,
+        "min_resolved_spokes": 2,
+        "min_silk_clearance": 0.0,
+        "min_text_height": 0.8,
+        "min_text_thickness": 0.08,
+        "min_through_hole_diameter": 0.3,
+        "min_track_width": 0.25,
+        "min_via_annular_width": 0.1,
+        "min_via_diameter": 0.5,
+        "solder_mask_to_copper_clearance": 0.0,
+        "use_height_for_length_calcs": true
+      },
+      "teardrop_options": [
+        {
+          "td_onpadsmd": true,
+          "td_onroundshapesonly": false,
+          "td_ontrackend": false,
+          "td_onviapad": true
+        }
+      ],
+      "teardrop_parameters": [
+        {
+          "td_allow_use_two_tracks": true,
+          "td_curve_segcount": 0,
+          "td_height_ratio": 1.0,
+          "td_length_ratio": 0.5,
+          "td_maxheight": 2.0,
+          "td_maxlen": 1.0,
+          "td_on_pad_in_zone": false,
+          "td_target_name": "td_round_shape",
+          "td_width_to_size_filter_ratio": 0.9
+        },
+        {
+          "td_allow_use_two_tracks": true,
+          "td_curve_segcount": 0,
+          "td_height_ratio": 1.0,
+          "td_length_ratio": 0.5,
+          "td_maxheight": 2.0,
+          "td_maxlen": 1.0,
+          "td_on_pad_in_zone": false,
+          "td_target_name": "td_rect_shape",
+          "td_width_to_size_filter_ratio": 0.9
+        },
+        {
+          "td_allow_use_two_tracks": true,
+          "td_curve_segcount": 0,
+          "td_height_ratio": 1.0,
+          "td_length_ratio": 0.5,
+          "td_maxheight": 2.0,
+          "td_maxlen": 1.0,
+          "td_on_pad_in_zone": false,
+          "td_target_name": "td_track_end",
+          "td_width_to_size_filter_ratio": 0.9
+        }
+      ],
+      "track_widths": [
+        0.0,
+        0.508,
+        1.27
+      ],
+      "tuning_pattern_settings": {
+        "diff_pair_defaults": {
+          "corner_radius_percentage": 80,
+          "corner_style": 1,
+          "max_amplitude": 1.0,
+          "min_amplitude": 0.2,
+          "single_sided": false,
+          "spacing": 1.0
+        },
+        "diff_pair_skew_defaults": {
+          "corner_radius_percentage": 80,
+          "corner_style": 1,
+          "max_amplitude": 1.0,
+          "min_amplitude": 0.2,
+          "single_sided": false,
+          "spacing": 0.6
+        },
+        "single_track_defaults": {
+          "corner_radius_percentage": 80,
+          "corner_style": 1,
+          "max_amplitude": 1.0,
+          "min_amplitude": 0.2,
+          "single_sided": false,
+          "spacing": 0.6
+        }
+      },
+      "via_dimensions": [
+        {
+          "diameter": 0.0,
+          "drill": 0.0
+        }
+      ],
+      "zones_allow_external_fillets": false
     },
     "ipc2581": {
       "dist": "",
@@ -283,8 +495,8 @@
     "last_paths": {
       "gencad": "",
       "idf": "",
-      "netlist": "",
+      "netlist": "../../../../../../",
-      "plot": "",
+      "plot": "/home/tgohle/Desktop/git/ToGo-Lab/0004-DenshaBekutoru/KiCad/0004-DenshaBekutoru_PCB_v0.2/",
       "pos_files": "",
       "specctra_dsn": "",
       "step": "",
@@ -295,7 +507,7 @@
   },
   "schematic": {
     "annotate_start_num": 0,
-    "bom_export_filename": "",
+    "bom_export_filename": "0004-DenshaBekutoru_v0.2.csv",
     "bom_fmt_presets": [],
     "bom_fmt_settings": {
       "field_delimiter": ",",
@@ -345,11 +557,35 @@
           "label": "DNP",
           "name": "${DNP}",
           "show": true
+        },
+        {
+          "group_by": false,
+          "label": "#",
+          "name": "${ITEM_NUMBER}",
+          "show": false
+        },
+        {
+          "group_by": false,
+          "label": "Sim.Device",
+          "name": "Sim.Device",
+          "show": false
+        },
+        {
+          "group_by": false,
+          "label": "Sim.Pins",
+          "name": "Sim.Pins",
+          "show": false
+        },
+        {
+          "group_by": false,
+          "label": "Description",
+          "name": "Description",
+          "show": false
         }
       ],
       "filter_string": "",
       "group_symbols": true,
-      "name": "Grouped By Value",
+      "name": "",
       "sort_asc": true,
       "sort_field": "Reference"
     },

README.md

@@ -1,12 +1,90 @@
-# DenshaBekutoru - Model Train Direction Sensor
+# 電車ベクトル (DenshaBekutoru)  
 
-Get **direction** and **speed** from motor power signals.  
+## Model Train Direction Sensor
-Target use case: **model trains**.
 
-- Detects polarity (+/–) to identify train direction  
+DenshaBekutoru is a small controller board for brick-built model locomotives.
-- Measures pulse width to calculate speed (% of maximum)  
-- Implemented with optocouplers and a state machine  
-- As small as possible, but I hope no SMD (beginner friendly)
 
-Project is in an early stage. Currently running tests on target hardware.  
+The target use case is: read the motor power signals, detect the current driving direction, and switch the headlights accordingly. The software is also prepared to derive speed information from the motor signal behaviour.
-More information and documentation will follow.
+
+This project is built around one practical problem: the motor is driven from an H-bridge, so the signal is noisy, polarity changes are not “clean logic”, and inductive spikes make direct evaluation difficult.
+
+## What it does
+
+- detects train direction from the motor power signal
+- evaluates two processed motor-side signals via analogue inputs
+- switches the front / rear lights according to direction
+- keeps the last valid direction if the train stops or the signal becomes unclear
+- is designed as small as possible for installation in brick-built locomotives
+
+## Technical approach
+
+The current version is built around:
+
+- optocoupler-based input isolation and signal conditioning
+- Arduino Pro Mini 5V as controller
+- software averaging of analogue inputs
+- startup calibration to adapt to different controllers and builds
+- threshold + hysteresis logic
+- simple state machine with direction memory
+- PWM-capable output pins for possible later LED dimming
+
+The main idea is not to read one raw signal and react immediately.  
+The idea is to turn a noisy motor signal into a stable direction decision.
+
+## Current status
+
+**Version 2 (beta) is built and working.**
+
+Current state:
+
+- [x] schematic finished
+- [x] PCB finished
+- [x] firmware finished for the current beta state
+- [x] three PCBs built and tested
+- [x] first boards handed over for real-life testing in a model railway club
+- [ ] Feedback and what to improve
+
+## Design goals
+
+- as small as possible
+- beginner-friendly where possible
+- no SMD if it can reasonably be avoided
+- easy to reproduce later as a DIY kit
+- modular PCB concept with main section, future-option section, and test section
+
+## Repository content
+
+Typical content of this repository:
+
+- `KiCad/` – schematic and PCB files
+- `firmware/` – Arduino test and controller software
+- documentation and pictures will be added step by step
+
+## Project status note
+
+This is still a beta project.
+
+The current hardware and software already work, but testing on real locomotives is still ongoing.  
+The next version will depend on real-life feedback from actual use.
+
+Possible next steps:
+
+- verify behaviour with different motor controllers
+- check robustness in real train builds
+- improve wiring / connector handling
+- finalise optional features like LED dimming
+- prepare a first “official” DIY kit version
+
+## Blog / documentation
+
+- Project overview:  https://togo-lab.io/?p=223
+- Hardware description:  https://togo-lab.io/?p=233
+- Software description:  https://togo-lab.io/?p=243
+
+## Short summary
+
+DenshaBekutoru is a small Arduino-based direction sensor for brick-built model trains.
+
+It reads the noisy motor signal from an H-bridge-driven setup, isolates and evaluates it, and switches the headlights automatically.
+
+The current beta version is working and now entering real-life testing.

firmware/ArduinoTest/DenshaBekutoru-0004_Version-0-2_ProMini_PCB2026-2_V01/DenshaBekutoru-0004_Version-0-2_ProMini_PCB2026-2_V01.ino

@@ -0,0 +1,287 @@
+/*
+  0004_DenshaBekutoru – 1st Version PCB
+ 
+  PCB Version      : 2026/02 (Order F016895)
+  Target dev board : Arduino Pro Mini 5V / 16 MHz (ATmega328P)
+  
+  ----------------------------------------------------------------------------
+  State machine (direction memory) + Hysteresis (Version A)
+  ----------------------------------------------------------------------------
+  We use two thresholds:
+    T_hold  (smaller): below -> treat as neutral and HOLD state
+    T_enter (larger) : above -> allow direction change (set by sign)
+
+  Behavior:
+    If |diff| <= T_hold  : hold direction
+    If |diff| >= T_enter : set direction by sign
+    Else (between)       : hold direction
+
+  Presets (implemented as multipliers of the calibrated VdiffThreshold):
+    T_hold  = 1.0 * VdiffThreshold
+    T_enter = 2.0 * VdiffThreshold
+
+  Inputs derived from v1, v2: diff = v1 - v2
+*/
+
+const unsigned long SAMPLE_WINDOW_MS = 100;   // averaging window per measurement
+const unsigned long SAMPLE_DELAY_US  = 500;   // delay between ADC samples (~2 kHz)
+
+const uint8_t ADC_PIN_1 = A0;  // Pro Mini A0 -> (PCB dependend!)
+const uint8_t ADC_PIN_2 = A1;  // Pro Mini A1 -> (PCB dependend")
+
+// Direction LEDs (avoid D0/D1 because you may want RX/TX later)
+const uint8_t LED_DIR1_PIN = 3;  // D3
+const uint8_t LED_DIR2_PIN = 9;  // D9
+
+const unsigned int LED_BLINK_ON_MS  = 150;
+const unsigned int LED_BLINK_OFF_MS = 150;
+
+// Serial output control (0 = no output, 1 = output)
+bool SerialOutputAllow = true;
+
+// ---- Calibration parameters ----
+const uint16_t AverageRepeat = 100;          // number of init measurements
+const float VdiffThresholdMargin = 1.50f;    // multiplier (e.g., 1.5 = +50% margin)
+const float VdiffThresholdMinVolts = 0.03f;  // floor in volts
+
+// ---- Hysteresis presets (multipliers of VdiffThreshold) ----
+const float THOLD_MULT  = 1.0f;  // T_hold  = THOLD_MULT  * VdiffThreshold
+const float TENTER_MULT = 2.0f;  // T_enter = TENTER_MULT * VdiffThreshold
+
+// Globals: latest measured averaged voltages
+float v1 = 0.0f;
+float v2 = 0.0f;
+
+// Calibration globals
+float VdiffBaseline = 0.0f;   // median(|V1-V2|) measured at boot (no movement)
+float VdiffThreshold = 0.0f;  // calibrated base threshold (used to derive T_hold/T_enter)
+
+// Hysteresis thresholds (derived once after calibration)
+float T_hold  = 0.0f;
+float T_enter = 0.0f;
+
+// Direction encoding:
+// 0 = NONE, 2 = DIR1, 3 = DIR2
+byte direction = 0;
+
+static inline float absf(float x) { return (x >= 0.0f) ? x : -x; }
+static inline float maxf(float a, float b) { return (a > b) ? a : b; }
+
+// -----------------------------------------------------------------------------
+// LED helpers
+// -----------------------------------------------------------------------------
+static void blinkLED(uint8_t pin, uint8_t times)
+{
+  for (uint8_t i = 0; i < times; i++) {
+    digitalWrite(pin, HIGH);
+    delay(LED_BLINK_ON_MS);
+    digitalWrite(pin, LOW);
+    delay(LED_BLINK_OFF_MS);
+  }
+}
+
+static void initBlinkSequence()
+{
+  // LED at Output 2 blinks 2 times
+  blinkLED(LED_DIR1_PIN, 2);
+
+  // LED at Output 3 blinks 3 times
+  blinkLED(LED_DIR2_PIN, 3);
+}
+
+static void applyDirectionOutputs()
+{
+  digitalWrite(LED_DIR1_PIN, LOW);
+  digitalWrite(LED_DIR2_PIN, LOW);
+
+  if (direction == 2) {
+    digitalWrite(LED_DIR1_PIN, HIGH);
+  } else if (direction == 3) {
+    digitalWrite(LED_DIR2_PIN, HIGH);
+  }
+}
+
+// -----------------------------------------------------------------------------
+// Measurement
+// -----------------------------------------------------------------------------
+static void measureAveragedVoltages()
+{
+  unsigned long startTime = millis();
+
+  unsigned long sum1 = 0;
+  unsigned long sum2 = 0;
+  unsigned long samples = 0;
+
+  while (millis() - startTime < SAMPLE_WINDOW_MS) {
+    sum1 += analogRead(ADC_PIN_1);
+    sum2 += analogRead(ADC_PIN_2);
+    samples++;
+    delayMicroseconds(SAMPLE_DELAY_US);
+  }
+
+  float avg1 = (float)sum1 / samples;
+  float avg2 = (float)sum2 / samples;
+
+  // Convert ADC value to voltage (default analog reference = Vcc ~ 5V)
+  v1 = avg1 * (5.0f / 1023.0f);
+  v2 = avg2 * (5.0f / 1023.0f);
+}
+
+// -----------------------------------------------------------------------------
+// Median helpers (for calibration)
+// -----------------------------------------------------------------------------
+static void sortFloatArray(float *a, uint16_t n)
+{
+  // Insertion sort (n=100 is small, OK)
+  for (uint16_t i = 1; i < n; i++) {
+    float key = a[i];
+    int16_t j = (int16_t)i - 1;
+    while (j >= 0 && a[j] > key) {
+      a[j + 1] = a[j];
+      j--;
+    }
+    a[j + 1] = key;
+  }
+}
+
+static float medianOfSortedFloatArray(const float *a, uint16_t n)
+{
+  if (n == 0) return 0.0f;
+  if (n & 1) {
+    return a[n / 2];
+  } else {
+    return (a[(n / 2) - 1] + a[n / 2]) * 0.5f;
+  }
+}
+
+// Calibrate baseline + VdiffThreshold once at boot/reset
+static void calibrateVdiffThreshold(uint16_t averageRepeat)
+{
+  if (averageRepeat < 1) averageRepeat = 1;
+  if (averageRepeat > 200) averageRepeat = 200; // RAM safety cap
+
+  float diffs[200];
+
+  for (uint16_t i = 0; i < averageRepeat; i++) {
+    measureAveragedVoltages();
+    diffs[i] = absf(v1 - v2); // baseline mismatch sample
+  }
+
+  sortFloatArray(diffs, averageRepeat);
+  VdiffBaseline = medianOfSortedFloatArray(diffs, averageRepeat);
+
+  // Calibrated base threshold with margin + floor
+  VdiffThreshold = maxf(VdiffBaseline * VdiffThresholdMargin, VdiffThresholdMinVolts);
+
+  // Derive hysteresis thresholds (Version A)
+  T_hold  = THOLD_MULT  * VdiffThreshold;
+  T_enter = TENTER_MULT * VdiffThreshold;
+}
+
+// -----------------------------------------------------------------------------
+// State machine with hysteresis (Version A)
+// -----------------------------------------------------------------------------
+static void updateDirectionFromVoltages()
+{
+  const float diff = v1 - v2;
+  const float absDiff = absf(diff);
+
+  // 1) Neutral region: HOLD
+  if (absDiff <= T_hold) {
+    return;
+  }
+
+  // 2) Strong region: allow direction change
+  if (absDiff >= T_enter) {
+    direction = (diff > 0.0f) ? (byte)2 : (byte)3;
+    return;
+  }
+
+  // 3) Deadband between T_hold and T_enter: HOLD
+  return;
+}
+
+// -----------------------------------------------------------------------------
+// Serial output
+// -----------------------------------------------------------------------------
+static void serialPrintAll()
+{
+  if (!SerialOutputAllow) return;
+
+  Serial.print("A2 for PB3  XTAL1, Pin2: ");
+  Serial.print(v1, 3);
+  Serial.print(" V   |   ");
+
+  Serial.print("A3 for PB4 XTAL2, Pin3: ");
+  Serial.print(v2, 3);
+  Serial.print(" V   |   ");
+
+  Serial.print("|V1-V2|: ");
+  Serial.print(absf(v1 - v2), 3);
+  Serial.print(" V   |   ");
+
+  Serial.print("VdiffBaseline: ");
+  Serial.print(VdiffBaseline, 3);
+  Serial.print(" V   |   ");
+
+  Serial.print("VdiffThreshold: ");
+  Serial.print(VdiffThreshold, 3);
+  Serial.print(" V   |   ");
+
+  Serial.print("T_hold: ");
+  Serial.print(T_hold, 3);
+  Serial.print(" V   |   ");
+
+  Serial.print("T_enter: ");
+  Serial.print(T_enter, 3);
+  Serial.print(" V   |   ");
+
+  Serial.print("direction: ");
+  Serial.println(direction);
+}
+
+// -----------------------------------------------------------------------------
+// Arduino entry points
+// -----------------------------------------------------------------------------
+void setup() {
+  Serial.begin(115200);
+
+  pinMode(ADC_PIN_1, INPUT);
+  pinMode(ADC_PIN_2, INPUT);
+
+  pinMode(LED_DIR1_PIN, OUTPUT);
+  pinMode(LED_DIR2_PIN, OUTPUT);
+
+  // Initial calibration (assumes no movement)
+  calibrateVdiffThreshold(AverageRepeat);
+
+  // Init blink sequence: 2x on D2, 3x on D3
+  initBlinkSequence();
+
+  // One measurement for initial display + initial direction
+  measureAveragedVoltages();
+  updateDirectionFromVoltages();
+  applyDirectionOutputs();
+
+  if (SerialOutputAllow) {
+    Serial.println("=== DenshaBekutoru Optocoupler Average Test (Arduino Pro Mini 5V/16MHz) ===");
+    Serial.print("AverageRepeat: ");
+    Serial.println(AverageRepeat);
+    Serial.print("THOLD_MULT: ");
+    Serial.print(THOLD_MULT, 2);
+    Serial.print("   TENTER_MULT: ");
+    Serial.println(TENTER_MULT, 2);
+  }
+
+  serialPrintAll();
+}
+
+void loop() {
+  measureAveragedVoltages();
+  updateDirectionFromVoltages();
+  applyDirectionOutputs();
+
+  serialPrintAll();
+
+  delay(300);
+}