Troubleshooting

This guide helps you diagnose and resolve common issues when using the AS5047U driver.

Common Error Messages

Error: CRC Errors

Symptoms:

  • Frequent CRC errors when reading angle
  • GetErrorFlags() returns CrcError flag
  • Unreliable angle readings

Causes:

  • SPI signal integrity issues (noise, reflections)
  • Incorrect SPI mode or timing
  • Loose connections
  • SPI speed too high
  • Power supply noise

Solutions:

  1. Reduce SPI Speed: Try lowering SPI frequency (e.g., 1-2 MHz instead of 10 MHz)
  2. Check SPI Mode: Ensure SPI Mode 1 (CPOL=0, CPHA=1) or Mode 3 (CPOL=1, CPHA=1)
  3. Enable Retries: Use retry parameter: encoder.GetAngle(3) for automatic retry
  4. Verify Connections: Check all SPI connections are secure
  5. Add Decoupling: Ensure proper decoupling capacitors (100nF + 10µF) near VDD
  6. Check Ground: Verify good ground connection between MCU and sensor
  7. Use 24-bit Frames: Switch to FrameFormat::SPI_24 for CRC protection

Error: Framing Errors

Symptoms:

  • GetErrorFlags() returns FramingError flag
  • Communication failures

Causes:

  • Incorrect SPI frame format
  • CS timing issues
  • SPI transaction length mismatch

Solutions:

  1. Check Frame Format: Ensure frame format matches sensor configuration
  2. Verify CS Timing: Check chip select assertion/deassertion timing
  3. Review SPI Implementation: Ensure transfer() method handles CS correctly

Error: AGC Warning

Symptoms:

  • GetErrorFlags() returns AgcWarning flag
  • AGC value at 0 or 255
  • Unreliable readings

Causes:

  • Magnet too close or too far from sensor
  • Weak magnetic field
  • Stray magnetic fields interfering

Solutions:

  1. Check Air Gap: Adjust magnet distance (0.5-3.0 mm recommended, 1.0 mm typical)
  2. Verify Magnet: Ensure diametrically magnetized magnet (6-12 mm diameter)
  3. Check Field Strength: Magnetic field should be 30-100 mT at sensor surface
  4. Remove Interference: Keep magnet away from ferromagnetic materials and motors
  5. Check Alignment: Ensure magnet is centered above sensor die

Error: Magnitude Half Warning

Symptoms:

  • GetErrorFlags() returns MagHalf flag
  • Magnetic field magnitude is half of regulated value

Causes:

  • Magnet too far from sensor
  • Weak magnetic field
  • Incorrect magnet type

Solutions:

  1. Reduce Air Gap: Move magnet closer to sensor (within 0.5-3.0 mm range)
  2. Check Magnet Strength: Verify magnet provides adequate field (30-100 mT)
  3. Verify Magnet Type: Ensure diametrically magnetized (2-pole) magnet

Hardware Issues

Device Not Responding

Symptoms:

  • No response from sensor
  • All readings return 0 or invalid values
  • SPI communication fails

Checklist:

  • Verify power supply voltage is 2.7V - 3.6V (3.3V typical)
  • Check all connections are secure (VDD, GND, CLK, MISO, MOSI, CS)
  • Verify SPI pin mapping (AS5047U uses reversed MISO/MOSI naming)
  • Check CS line is properly controlled (active low)
  • Verify SPI mode is correct (Mode 1 or Mode 3)
  • Use oscilloscope/logic analyzer to verify bus activity
  • Check for short circuits or incorrect wiring

Communication Errors

Symptoms:

  • Timeout errors
  • CRC/checksum errors
  • Inconsistent readings

Solutions:

  • Check Bus Speed: Ensure SPI speed is within specifications (up to 10 MHz, 4 MHz recommended)
  • Verify Signal Integrity: Check for noise, reflections, or signal degradation
  • Ensure Proper Termination: Verify proper bus termination
  • Check for Loose Connections: Inspect all connections
  • Reduce SPI Speed: Try lower frequency if issues persist
  • Add Pull-ups: Ensure proper pull-up resistors if needed

Incorrect Angle Readings

Symptoms:

  • Angle values don’t change when rotating
  • Angle values jump erratically
  • Angle values are always zero

Causes:

  • Magnet not properly positioned
  • Incorrect magnet type
  • Stray magnetic fields
  • Sensor not initialized

Solutions:

  1. Check Magnet Placement: Verify magnet is centered and at correct distance
  2. Verify Magnet Type: Ensure diametrically magnetized (2-pole) magnet
  3. Check for Interference: Remove sources of stray magnetic fields
  4. Verify Initialization: Ensure SPI bus is properly initialized
  5. Check Error Flags: Read error flags to diagnose specific issues

Software Issues

Compilation Errors

Error: “No matching function”

Solution:

  • Ensure you’ve implemented the transfer() method in your SPI interface
  • Check method signature matches: void transfer(const uint8_t* tx, uint8_t* rx, std::size_t len)
  • Verify you’re inheriting from as5047u::SpiInterface<YourClass>

Error: “Undefined reference”

Solution:

  • Verify you’re linking the driver source file (as5047u.cpp)
  • Check include paths are correct
  • Ensure C++20 standard is enabled: -std=c++20

Error: “Template instantiation failed”

Solution:

  • Verify your SPI interface class is properly templated: class MySPI : public as5047u::SpiInterface<MySPI>
  • Check that all required methods are implemented

Runtime Errors

Initialization Fails

Checklist:

  • SPI bus interface is properly initialized
  • Hardware connections are correct
  • SPI configuration matches sensor requirements
  • Device is powered and ready
  • CS pin is correctly configured

Unexpected Behavior

Checklist:

  • Verify configuration matches your use case
  • Check for timing issues (add delays if needed)
  • Review error handling code
  • Verify frame format is correct
  • Check error flags for diagnostic information

Debugging Tips

Enable Debug Output

Add debug prints to your SPI implementation:

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void transfer(const uint8_t* tx, uint8_t* rx, std::size_t len) {
    printf("SPI Transfer: len=%zu\n", len);
    // ... your SPI code
}

Use DumpStatus()

Print comprehensive sensor status:

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encoder.DumpStatus();

This prints angle, velocity, AGC, magnitude, and error flags.

Check Error Flags

Always check error flags after operations:

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uint16_t angle = encoder.GetAngle();
AS5047U_Error errors = encoder.GetStickyErrorFlags();
if (errors != AS5047U_Error::None) {
    printf("Errors: 0x%04X\n", static_cast<uint16_t>(errors));
}

Use a Logic Analyzer

For bus communication issues, a logic analyzer can help:

  • Verify correct protocol timing
  • Check for signal integrity issues
  • Validate data being sent/received
  • Debug CS timing issues

Verify SPI Pin Mapping

Important: AS5047U uses reversed SPI pin naming:

  • MCU MOSI → AS5047U MISO (data from MCU to sensor)
  • MCU MISO → AS5047U MOSI (data from sensor to MCU)

Double-check your wiring matches this!

FAQ

Q: What SPI frame format should I use?

A: For most applications, use FrameFormat::SPI_24 - it provides CRC protection with good throughput. Use SPI_16 for maximum speed (no CRC), or SPI_32 for daisy-chain applications.

Q: How do I know if my magnet is positioned correctly?

A: Check the AGC value - it should be between 10-245 (not at limits 0 or 255). Also check magnitude - it should be in a reasonable range (typically 5000-15000). Use DumpStatus() to see all diagnostics.

Q: Can I use multiple AS5047U sensors on the same SPI bus?

A: Yes, use FrameFormat::SPI_32 with different pad bytes for each sensor. Each sensor needs its own CS line.

Q: Why are my angle readings noisy?

A: Enable adaptive filtering: encoder.SetAdaptiveFilter(true) and adjust filter parameters. Also check magnet placement and ensure proper decoupling capacitors.

Q: How do I calibrate the zero position?

A: Read the current angle when at your desired zero position, then call encoder.SetZeroPosition(current_angle). See Example 7 for details.

Q: What happens if I program OTP incorrectly?

A: OTP programming is irreversible. If you program incorrect settings, you cannot change them. Always verify settings before programming OTP.

Getting More Help

If you’re still experiencing issues:

  1. Check the API Reference for method details
  2. Review Examples for working code
  3. Search existing issues on GitHub
  4. Open a new issue with:
    • Description of the problem
    • Steps to reproduce
    • Hardware setup details (MCU, wiring, magnet type)
    • Error messages/logs
    • Output from DumpStatus()

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