arduino/firmware/mega/troubleshoot.md

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:

   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:

   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:

   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:

   // 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:

   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

3. 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