Arduino library for A1301 and A1302 magnetometer.

The A1301 and A1302 are continuous-time, Ratio-metric, linear Hall-effect sensors. They are optimized to accurately provide a voltage output that is proportional to an applied magnetic field. These devices have a quiescent output voltage that is 50% of the supply voltage. This voltage level is a.k.a. the midPoint.

Two output sensitivity options are provided: 2.5 mV/G typical for the A1301, and 1.3 mV/G typical for the A1302. (from datasheet)

The following 5 classes are supported:

Other, more or less, compatible sensors are welcome. (see future below.)

The library is experimental and need more testing. Feedback, issues and improvements are welcome, Please open an issue on GitHub.

//  always check datasheet.
//
//    PIN    A1301
//    ===============
//     1     GND
//     2     DATA
//     3     VDD +5V

#include "A1301.h"

• HALL(uint8_t pin) base class constructor. pin is the analogPin to read from.
• A1301(uint8_t pin) constructor.
• A1302(uint8_t pin) constructor.
• A1324(uint8_t pin) constructor.
• A1325(uint8_t pin) constructor.
• A1326(uint8_t pin) constructor.

• void begin(float voltage, uint16_t steps) Sets the parameters voltage and number of steps of the internal ADC. Note this allows to update the voltage runtime. Steps must be larger than zero.
• void setMidPoint(float midPoint) the value of midPoint depends on the internal ADC. It is the value where there is no (zero) magnetic field. Note it does not need to be a whole value. This allows quite precise tuning.
• float autoMidPoint(uint8_t times = 100) assumes zero field. Averages multiple (default 100) samples to set the midPoint. Uses internal ADC. Also returns the found midPoint. -- float getMidPoint() returns the current midPoint.
• void setSensitivity(float sensitivity) overrule default sensitivity. Use with care.
• float getSensitivity() return the set / current sensitivity.

• float raw(uint8_t times = 1) raw analog measurement.
• float read(uint8_t times = 1) raw measurement converted to Gauss. Can be positive (North) or negative (South). Returns Gauss.
• float readExt(float raw) to be used with external ADC. Note: raw is an ADC measurement, not a voltage. Can be positive (North) or negative (South). Returns Gauss. Can also be used for testing, e.g. replay of a series of data.

• bool isNull() last read is zero.
• bool isNorth() last read is above than zero.
• bool isSouth() last read is below zero.
• bool isRising() trend (last 2 reads) is upward.
• bool isFalling() trend (last 2 reads) is downward.
• float lastGauss() returns last measurement in Gauss.
• float prevGauss() returns previous measurement in Gauss.
• float deltaGauss() returns last - previous measurement.

Experimental.

• float determineNoise(uint8_t times = 2) estimates noise level around measurements. times will be forced to be at least 2. Does not affect lastGauss or prevGauss values.
• float angle() returns atan2(prevGauss, lastGauss). Indicator of change. Returns angle in radians. For degrees multiply by 180/PI.

Experimental saturation level.

• void setMaxGauss(float maxGauss) set the saturation level. If maxGauss < 0 the absolute value is set.
• float getMaxGauss() returns the set saturation level.
• bool isSaturated() true when ADC (lastRead) seems to max out.
• float saturationLevel() returns value between 0..100%, or beyond!

• float Tesla(float Gauss) convenience convertor.
• float mTesla(float Gauss) convenience convertor.
• float uTesla(float Gauss) convenience convertor.

• improve documentation
• buy hardware A1301 / A1302 / etc...
• test with hardware (again)

• unit tests
• test isSaturated() + saturationLevel()
  • limits might be sensor dependant.
• investigate atan2(prevGauss, lastGauss)
  • angle indicates relative delta compared to magnitude and direction.
  • 45 & 315 degrees is no change.

• Possible compatible
  • HoneyWell - SS39ET/SS49E/SS59ET
  • HoneyWell - SS490 Series
• temperature correction functions?
  • see datasheet.
• relative flux = prevGauss / lastGauss
  • smaller 1 => increasing
  • larger 1 => decreasing
  • negative => flipping

(thinking out loud section)

• isEast() and isWest() meaning?
• influence of angle of the field-lines?
• defaults for parameters of some functions?

• printable interface

  • does not add much.

• can the strength of the signal be converted to distance?

  • for a given magnet maybe
  • repeatability + noise is a problem.

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Thank you,