Ajout prise en charge ESP-Display
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doc/PROGRAMMING_TRACK.md
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doc/PROGRAMMING_TRACK.md
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# DCC Programming Track Implementation
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## Overview
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The DCC-Bench uses the **LM18200 H-Bridge** for both normal DCC operation AND programming track functionality. Since this is a dedicated test bench with only one locomotive at a time, the same driver can handle both modes without issue.
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## Why This Works
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### Traditional DCC Systems
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- **Main Track**: High current (3-5A) for running multiple locomotives
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- **Programming Track**: Limited current (250mA max) with ACK detection
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### DCC-Bench Approach
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- **Single Track**: Only one locomotive under test
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- **LM18200**: Can handle both operation and programming
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- **Current Limit**: LM18200 has built-in current limiting
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- **ACK Detection**: Monitor current draw through sense resistor
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## Hardware Requirements
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### Essential Components
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1. **LM18200 H-Bridge** (already in design)
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- Dual-purpose: DCC signal amplification + programming
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- Built-in current limiting and thermal protection
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- Pins: GPIO 18 (Signal A), GPIO 19 (Signal B), GPIO 23 (Brake)
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2. **Current Sense Resistor** (0.1Ω, 1W)
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- Monitor programming track current
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- Placed in series with LM18200 output
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- Creates voltage drop proportional to current
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3. **ADC Input for ACK Detection**
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- ESP32 ADC pin (e.g., GPIO 35)
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- Connected to current sense resistor voltage
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- Detects 60mA+ ACK pulse from decoder
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### Optional Enhancements
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- **Current Limiter Circuit**: Additional 250mA fuse for extra safety
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- **LED Indicator**: Visual feedback during programming
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- **Isolation**: Optocouplers for additional protection
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## Wiring Diagram
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```
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ESP32 GPIO 18 ──────┐
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├──> LM18200 ──> Current Sense ──> TRACK
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ESP32 GPIO 19 ──────┘ │
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│
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ESP32 GPIO 35 (ADC) <──── Voltage Divider ┘
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(for ACK detect)
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Current Sense Circuit:
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0.1Ω, 1W
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Track+ ────┬──────╱╲╲╲───── LM18200 Output
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│
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├─── 1kΩ ───┬──── GPIO 35 (ADC)
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│ │
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│ 10kΩ
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│ │
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Track- ────┴───────────┴──── GND
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```
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## DCC Programming Protocol
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### Service Mode (Programming Track)
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The DCC-Bench implements NMRA DCC Service Mode:
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1. **Factory Reset** (CV8 = 8)
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- Resets decoder to factory defaults
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- Standard NMRA reset command
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2. **Set Address**
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- **Short Address (1-127)**: Write to CV1
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- **Long Address (128-10239)**: Write to CV17 + CV18
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- Automatically updates CV29 for address mode
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3. **CV Read** (Bit-wise Verify)
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- Tests each bit (0-7) individually
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- More reliable than direct read
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- Requires ACK detection for each bit
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4. **CV Write** (Write + Verify)
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- Writes value with 3 retry attempts
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- Verifies write with ACK detection
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- NMRA-compliant packet structure
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### ACK Detection
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**How It Works:**
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1. Decoder receives programming command
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2. If command is valid and matches, decoder draws 60mA pulse for 6ms
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3. Current sense resistor creates voltage spike
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4. ESP32 ADC detects voltage above threshold
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5. ACK confirmed = command successful
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**Threshold Values:**
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- **ACK Current**: 60mA minimum (NMRA standard)
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- **ACK Duration**: 6ms typical
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- **Timeout**: 20ms wait for response
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## Current Implementation Status
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### ✅ Implemented
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- NMRA-compliant packet encoding
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- Service mode packet structure (22-bit preamble)
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- Factory reset command (CV8 = 8)
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- Address programming (short and long)
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- CV read (bit-wise verify method)
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- CV write (write + verify)
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- Programming screen UI with numeric keypad
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### ⚠️ Needs Hardware
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- **ACK Detection**: Currently returns `true` (assumed success)
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- **Current Sensing**: ADC reading not yet implemented
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- **Calibration**: Threshold tuning for specific hardware
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## Adding ACK Detection
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### Step 1: Wire Current Sense
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```cpp
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// Add current sense resistor (0.1Ω) in series with track output
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// Connect voltage divider to ESP32 GPIO 35 (ADC1_CH7)
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```
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### Step 2: Update `waitForAck()` Method
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```cpp
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bool DCCGenerator::waitForAck() {
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#define CURRENT_SENSE_PIN 35
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#define ACK_THRESHOLD 100 // Adjust based on calibration
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unsigned long startTime = millis();
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// Wait up to 20ms for ACK pulse
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while (millis() - startTime < 20) {
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int adcValue = analogRead(CURRENT_SENSE_PIN);
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// If current spike detected (60mA+)
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if (adcValue > ACK_THRESHOLD) {
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Serial.println("ACK detected!");
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return true;
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}
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delayMicroseconds(100);
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}
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Serial.println("No ACK");
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return false;
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}
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```
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### Step 3: Calibrate Threshold
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```cpp
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// Test with known-good decoder
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// Measure ADC values during programming
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// Adjust ACK_THRESHOLD to reliably detect 60mA pulse
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```
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## Safety Features
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### Built-in Protection
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1. **LM18200 Thermal Shutdown**: Protects against overheating
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2. **Current Limiting**: Prevents excessive current draw
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3. **Brake Pin**: Emergency stop capability (GPIO 23)
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### Software Safety
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1. **Power-Off on Mode Change**: Prevents accidental high current
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2. **CV Range Validation**: Only allows CV 1-1024
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3. **Address Range Check**: Validates 1-10239
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4. **Write Verification**: Confirms successful programming
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### Recommended Additions
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1. **250mA Fuse**: Additional protection for programming track
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2. **Timeout Handling**: Abort if no response after retries
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3. **Error Logging**: Track failed programming attempts
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## Usage
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### From Touchscreen UI
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1. **Enter DCC Mode**
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- Press [MODE] button until "DCC" selected
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- Press [POWER] to enable
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2. **Open Programming Screen**
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- Press [PROG] button (appears in DCC mode)
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3. **Factory Reset**
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- Press [FACTORY RESET] button
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- Wait for confirmation (or timeout)
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4. **Set Address**
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- Enter address using keypad (field auto-selected)
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- Press [SET ADDR] button
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- Wait for verification
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5. **Read CV**
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- Enter CV number (tap CV field, then use keypad)
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- Press [READ] button
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- Value appears in CV Value field
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6. **Write CV**
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- Enter CV number and value
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- Press [WRITE] button
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- Wait for verification
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### From Serial Monitor
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```cpp
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DCCGenerator dcc;
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// Factory reset
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dcc.factoryReset();
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// Set address to 42
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dcc.setDecoderAddress(42);
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// Read CV7 (Version)
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uint8_t version;
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if (dcc.readCV(7, &version)) {
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Serial.printf("Decoder version: %d\n", version);
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}
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// Write CV3 (Acceleration) = 20
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dcc.writeCV(3, 20);
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```
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## Troubleshooting
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### No ACK Detected
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**Possible Causes:**
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- Current sense not connected
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- Threshold too high/low
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- Decoder not responding
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- Wrong CV number/value
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**Solutions:**
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1. Verify current sense wiring
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2. Test with multimeter (should see 60mA spike)
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3. Calibrate ADC threshold
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4. Try factory-reset decoder first
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5. Check decoder is DCC-compatible
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### Programming Fails
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**Check:**
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1. Only one locomotive on track
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2. Decoder supports NMRA DCC
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3. Track connections solid
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4. LM18200 powered and enabled
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5. No shorts on track
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### Inconsistent Results
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**Causes:**
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- Dirty track/wheels
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- Poor electrical contact
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- Noise on current sense line
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- Decoder in bad state
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**Solutions:**
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1. Clean track and wheels
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2. Verify all connections tight
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3. Add filtering capacitor on ADC input
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4. Factory reset decoder
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5. Check for ground loops
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## Technical References
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### NMRA Standards
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- **S-9.2.3**: Service Mode (Programming Track)
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- **RP-9.2.3**: Recommended Practices for Service Mode
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- **CV Definitions**: Standard configuration variables
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### Service Mode Packet Format
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```
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┌──────────┬───┬──────────┬───┬──────────┬───┬──────────┬───┐
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│ Preamble │ 0 │ Address │ 0 │ Instruction│ 0 │ Checksum│ 1 │
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│ (22 bits)│ │ (1 byte) │ │ (1-2 byte) │ │ (1 byte) │ │
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└──────────┴───┴──────────┴───┴──────────┴───┴──────────┴───┘
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```
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### CV Addresses
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- **CV1**: Short Address (1-127)
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- **CV7**: Decoder Version
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- **CV8**: Manufacturer ID (8 = Factory Reset)
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- **CV17-18**: Long Address (128-10239)
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- **CV29**: Configuration (address mode, speed steps, etc.)
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## Future Enhancements
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1. **Advanced Programming**
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- Operations mode (programming on main track)
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- Read on Main (RailCom support)
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- Indexed CV access
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2. **Decoder Detection**
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- Auto-detect decoder manufacturer (CV8)
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- Read decoder version (CV7)
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- Capability detection
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3. **Batch Programming**
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- Save/load decoder configurations
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- Bulk CV programming
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- Profile management
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4. **Diagnostics**
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- Current monitoring during operation
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- ACK pulse visualization
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- Programming success statistics
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