Troubleshooting

Symptoms you may see while bringing up an AS5047U, their causes and the fix for each, cheapest check first.

Start with DumpStatus(): it prints the angle, velocity, AGC, magnitude, ERRFL, every DIA bit and the settings registers in one go, and tells transport problems (all zeros, all ones) apart from magnet problems (AGC at a limit).

Every register reads 0 or 0x3FFF

Cause	Check	Fix
No supply, or TEST not grounded	3.0 V to 3.6 V (3.3 V mode) or 4.5 V to 5.5 V (5 V mode) on VDD; TEST at GND	Fix the supply; ground TEST
MISO not connected, or floating	Probe MISO during a frame: it must toggle	Wire MISO; 0x3FFF everywhere means MISO stays high
Wrong SPI mode	Mode 1: CLK idles low, data sampled on the falling edge	Set mode 1; modes 0, 2 and 3 do not work
CSn held low across several frames	CSn must go high after each transfer()	One frame per chip-select period (Porting)
5 V mode with a 3.3 V MCU	VIH is 0.7 × VDD = 3.5 V at 5 V	Level-shift, or run the sensor in 3.3 V mode

CRC or framing errors

CrcError or FramingError in the sticky flags or in GetErrorFlags() (the chip saw a bad MOSI frame), or ReplyCrcError in the sticky flags (the driver saw a bad MISO frame).

Cause	Fix
Clock too fast for the wiring	Drop to 1 MHz; the limit is 10 MHz on a short, clean bus
CSn set-up or high time under 350 ns	Add chip-select set-up and hold cycles in your SPI driver
A frame of the wrong length	transfer() must clock exactly len bytes (2, 3 or 4)
Noise on CLK	Shorter traces, series resistor at the MCU, solid ground between MCU and sensor

Pass a retries value (for example GetAngle(2)) to repeat a read the chip flagged. Retries hide occasional errors; they do not fix a wiring problem.

AGC at 0 or 255

AGC	Meaning	Fix
255, MagHalf set	Field too weak: magnet too far, too small or not diametrically magnetized	Move it closer; the field must be 35 mT to 70 mT at the die
0	Field too strong	Move the magnet away
Changes with angle	Magnet off-center or tilted	Center it on the package axis

The angle is wrong or noisy

Symptom	Cause	Fix
Angle runs backwards	DIR	SetDirection(true) makes clockwise (seen from the top of the chip) increase
Zero is in the wrong place	Zero position not set, or lost at power-off	SetZeroPosition(), then OTP programming to keep it
Noisy at standstill	Filter at high K, DAEC on	SetFilterPreset(FilterPreset::LowNoise), SetDynamicAngleCompensation(false)
Lags at high speed	DAEC off, or reading ANGLEUNC	SetDynamicAngleCompensation(true), SetAngleOutputSource(UseANGLECOM)
The ABI count lags by a step after a reversal	ABI hysteresis (1 LSB of 11 bit, 0.17°, by default)	SetHysteresis(SETTINGS3::Hysteresis::NONE)

Velocity is not zero at standstill

The velocity is a 14-bit two's-complement value in 24.141 °/s per LSB. At standstill the datasheet gives 5.8 °/s rms noise at K = 0 and 244.9 °/s at K = 6 (Figure 17), so ±1 LSB with the magnet still is normal, and more is normal with a high filter K. Detect "stopped" with a threshold, not with zero.

Settings are gone after a power cycle

The settings registers are volatile until OTP is burned: this is expected. Burn them with ProgramOTP() once you are sure of them (OTP programming).

A setter returns false

The value did not read back as written, or a frame of the write failed. The driver prints nothing; clear the sticky flags, call the setter again and read them:

Sticky flags after the call	Cause
CrcError	The write frame was corrupted on the bus: see CRC errors above
FramingError or CommandError	Frame length or chip select
BusError	The port's transfer() returned false
ReplyCrcError	A reply was corrupted on MISO: see CRC errors above
None	The register or field is read-only, or the value does not stick

Call the setter with a retries value to retry automatically.