# Troubleshooting Guide (O fok wat nou boek)

## LED Status Indicators
The device uses two LEDs for status indication:
- LED A (Pin 3): Activity indicator
- LED B (Pin 5): Error indicator

### LED Error Patterns
- 4 slow blinks: RTC initialization failure
- 4 medium blinks: RTC lost power (time reset required)
- 2 slow blinks: SD card initialization failure
- 10 quick blinks: Multiple consecutive Modbus read errors
- Continuous error blinks: Number of blinks indicates error count in current cycle

## Hardware Diagnostics

### RTC (Real-Time Clock) Module

1. Power Check:
   - Measure voltage between VCC and GND pins (should be 5V ±0.2V)
   - Check if backup battery is installed and voltage is above 2.5V
   - Verify proper connection to SDA (Pin 20) and SCL (Pin 21)

2. Communication Test:
   ```cpp
   if (!rtc.begin()) {
     Serial.println("RTC Failed");
   } else {
     DateTime now = rtc.now();
     Serial.print(now.year(), DEC);
     Serial.print('/');
     Serial.print(now.month(), DEC);
     Serial.print('/');
     Serial.print(now.day(), DEC);
   }
   ```

3. Common RTC Issues:
   - No communication: Check I2C pullup resistors
   - Incorrect time: Replace backup battery
   - Random resets: Check for loose connections
   - Time drift: Environmental temperature too high

### SD Card Module

1. Physical Inspection:
   - Verify card is properly seated
   - Check pin connections:
     * CS → Pin 53
     * MOSI → Pin 51
     * MISO → Pin 50
     * SCK → Pin 52

2. Diagnostic Test:
   ```cpp
   void testSD() {
     if (!sd.begin(SD_CONFIG)) {
       Serial.println("SD initialization failed!");
       return;
     }
     
     // Test file creation
     File testFile;
     if (!testFile.open("test.txt", FILE_WRITE)) {
       Serial.println("File creation failed!");
       return;
     }
     
     // Test writing
     if (!testFile.println("Test data")) {
       Serial.println("Write failed!");
     }
     
     testFile.close();
     Serial.println("SD test passed!");
   }
   ```

3. Common SD Issues:
   - Card not detected: Try reformatting to FAT32
   - Write errors: Check card write-protect switch
   - Random failures: Power supply issues
   - Slow performance: Reduce SPI clock speed

### RS485/Modbus Communication

1. Physical Layer Test:
   - Measure differential voltage between A and B lines:
     * Idle state: ~0.9V to -0.9V
     * Active state: ~2V to -2V
   - Check termination resistors (120Ω)
   - Verify ground reference

2. Communication Test:
   ```cpp
   void testModbus() {
     // Set device to receive mode
     digitalWrite(DE_RE_PIN, LOW);
     
     // Try reading first register
     uint8_t result = node.readHoldingRegisters(0, 1);
     if (result == node.ku8MBSuccess) {
       Serial.println("Modbus communication OK");
     } else {
       Serial.print("Modbus error: ");
       Serial.println(result);
     }
   }
   ```

3. Common Modbus Issues:
   - No response: Check baud rate settings
   - Intermittent communication: Check cable shielding
   - Garbled data: A/B lines reversed
   - Timeout errors: Increase retry count

## System-wide Issues

1. Power Supply Problems:
   - Symptoms:
     * Random resets
     * SD card write failures
     * Intermittent communication
   - Solutions:
     * Use separate power supply for RS485 device
     * Add decoupling capacitors
     * Check for ground loops

2. Environmental Issues:
   - EMI interference: Shield cables
   - Temperature: Keep below 50°C
   - Vibration: Secure all connections
   - Moisture: Use conformal coating

3. Software Lockups:
   - Implement watchdog timer
   - Add error recovery routines
   - Monitor free memory

## Maintenance Checklist

1. Weekly:
   - Check LED status patterns
   - Verify log file creation
   - Monitor data consistency

2. Monthly:
   - Backup SD card data
   - Check all connections
   - Clean card contacts
   - Verify RTC accuracy

3. Quarterly:
   - Update firmware if needed
   - Check power supply voltage
   - Test communication reliability
   - Clean enclosure and ventilation

## Emergency Recovery

1. If system stops logging:
   - Check LED error patterns
   - Review serial debug output
   - Power cycle the device
   - Check SD card in computer
   
2. Data recovery:
   - Copy all files before removing card
   - Use file recovery software if needed
   - Check file timestamps for gaps

3. System reset:
   - Hold reset button for 5 seconds
   - Reformat SD card if necessary
   - Reconfigure RTC if needed


## More Power-Related Issues

#### Symptoms & Diagnostics:
- Random resets
  * Measure input voltage during operation (should be 9V ±0.5V)
  * Check voltage stability during Modbus communication
  * Monitor voltage drops during SD card writes
  
- SD card write failures
  * Monitor 5V rail during write operations (should remain above 4.8V)
  * Check for voltage sags when LED indicators activate
  * Test with different power supplies to isolate issue

- Intermittent communication
  * Measure RS485 supply voltage under load
  * Check for ground potential differences
  * Monitor voltage stability during transmission

#### Solutions:
1. Power Supply Improvements:
   - Use a regulated 9V power supply rated for at least 1A
   - Add local decoupling capacitors:
     * 100μF electrolytic near voltage input
     * 10μF tantalum at Arduino VIN
     * 0.1μF ceramic at each IC power pin
   - Consider using a dedicated 5V regulator for sensitive components

2. Ground Loop Prevention:
   - Keep ground returns short and direct
   - Create a single ground point near the Arduino
   - Use star grounding topology
   - Add 100Ω resistor in RS485 ground line
   - Consider optical isolation for RS485

3. Noise Reduction:
   - Separate digital and analog grounds
   - Use shielded cables for RS485
   - Add ferrite beads on power lines
   - Keep high-current paths away from sensitive signals

### 2. Voltage Stability Issues

#### Common Problems:
1. Brownouts
   - Symptoms:
     * RTC resets
     * Corrupted SD card writes
     * Modbus communication errors
   - Solutions:
     * Add bulk capacitance (1000μF or larger)
     * Use higher current power supply
     * Monitor power quality with oscilloscope

2. Voltage Ripple
   - Symptoms:
     * Erratic behavior
     * Communication errors
     * Incorrect sensor readings
   - Solutions:
     * Add LC filter on power input
     * Use linear regulator instead of switching
     * Increase decoupling capacitance

3. EMI/RFI Issues
   - Symptoms:
     * Interference during transmission
     * Data corruption
     * System lockups
   - Solutions:
     * Shield power supply cables
     * Add common-mode chokes
     * Use metal enclosure as shield
     * Add TVS diodes for protection

[Previous sections remain the same until Component-Specific Power Solutions]

### 3. Component-Specific Power Solutions

#### 3.1 SD Card Module Power Management

1. Voltage Requirements:
   - Operating voltage: 3.3V ±0.3V
   - Maximum current draw: ~100mA during writes
   - Peak current during initialization: ~200mA

2. Recommended Power Configuration:
   - Primary Solution:
     * Use AMS1117-3.3V dedicated regulator
     * Input capacitor: 10μF tantalum
     * Output capacitor: 22μF tantalum
     * Bulk capacitor: 100μF electrolytic
     * Bypass capacitor: 0.1μF ceramic

3. Implementation Details:
   ```cpp
   // Code to detect power-related SD issues
   bool checkSDPower() {
     if (!sd.begin(SD_CONFIG)) {
       // Try power cycling SD card if available
       digitalWrite(SD_POWER_PIN, LOW);
       delay(100);
       digitalWrite(SD_POWER_PIN, HIGH);
       delay(100);
       return sd.begin(SD_CONFIG);
     }
     return true;
   }
   ```

4. PCB Layout Recommendations:
   - Keep power traces minimum 20mil width
   - Use ground plane under SD module
   - Place decoupling caps within 10mm
   - Separate digital and analog grounds

#### 3.2 RS485 Interface Power Solutions

1. Power Requirements:
   - Operating voltage: 5V ±0.25V
   - Typical current: 50mA
   - Maximum current: 250mA during transmission

2. Isolation Solutions:
   - Recommended Components:
     * ISO7721 digital isolator
     * B0505S-1W isolated DC-DC converter
     * 120Ω termination resistors (0.25W)
     * TVS diodes: SMBJ6.5CA

3. Protection Circuit:
   ```
   VCC (5V) ----[10Ω]----+----[0.1μF]----GND
                         |
                     [TVS Diode]
                         |
   RS485_A ----[100Ω]---+----[MAX485]
   ```

4. Noise Mitigation:
   - Add common-mode choke (100μH)
   - Use split ground plane
   - Implement cable shield grounding
   - Add bi-directional TVS protection

#### 3.3 RTC Module Power Management

1. Primary Power:
   - Operating voltage: 5V ±0.5V
   - Current consumption: ~1.5mA
   - Backup current: ~3μA

2. Backup Power Solutions:
   - Primary Option: CR2032 Battery
     * Expected life: 3-5 years
     * Monitor voltage threshold: 2.5V
     * Add schottky diode for protection
   
   - Alternative: Super Capacitor
     * Recommended: 1F, 5.5V
     * Charge resistor: 1kΩ
     * Backup duration: ~1 week

3. Power Monitoring:
   ```cpp
   bool checkRTCPower() {
     float backupVoltage = analogRead(RTC_BATT_PIN) * (5.0 / 1023.0);
     if (backupVoltage < 2.5) {
       Serial.println("RTC backup voltage low!");
       return false;
     }
     return true;
   }
   ```

4. Temperature Compensation:
   - Add temperature sensor (DS18B20)
   - Monitor correlation with time drift
   - Implement software correction

#### 3.4 Arduino MEGA Power Requirements

1. Voltage Inputs:
   - VIN (recommended): 7-12V
   - 5V USB: 5V ±0.25V
   - Maximum current: 500mA
   - Peak current: 800mA

2. Power Distribution:
   - Main regulator bypassing:
     * 47μF electrolytic on VIN
     * 0.1μF ceramic on 5V
     * 10μF tantalum on 3.3V


4. Power Debugging:
   - Monitor VIN with voltage divider
   - Check 5V rail stability
   - Measure ground bounce
   - Track current consumption

#### 3.5 Power Integration Guidelines

1. System Power Budget:
   ```
   Component          Typical     Peak
   --------------------------------------
   Arduino MEGA       100mA      200mA
   SD Card            50mA       200mA
   RS485              50mA       250mA
   RTC                2mA        3mA
   LEDs               20mA       40mA
   --------------------------------------
   Total:             222mA      693mA
   ```

2. Power Supply Selection:
   - Minimum rating: 12V @ 1A
   - Recommended: 12V @ 2A
   - Consider linear vs switching
   - Add 50% safety margin

3. Decoupling Network:
   ```
   Location           Capacitor
   --------------------------------------
   Input Power        1000μF electrolytic
   VIN                47μF electrolytic
   5V Rail            10μF tantalum
   3.3V Rail          22μF tantalum
   Each IC            0.1μF ceramic
   ```

4. Ground Management:
   - Implement star grounding
   - Separate analog/digital
   - Use ground plane
   - Monitor ground differential