GY-63_MS5611/libraries/AS5600/README.md

AS5600

Arduino library for AS5600 magnetic rotation meter.

Description

AS5600

AS5600 is a library for an AS5600 based magnetic rotation meter.

Warning: experimental

The sensor can measure a full rotation in 4096 steps. The precision is therefore limited to 0.1°. Noise levels unknown, but one might expect it to be effected by electric and or magnetic signals in the environment. Also unknown is the influence of metals near the sensor or an unstable or fluctuating power supply.

I2C Address

The I2C address of the AS5600 is always 0x36.

To use more than one AS5600 on one I2C bus, see Multiplexing below.

OUT pin

The sensor has an output pin named OUT. This pin can be used for an analogue or PWM output signal.

See Analogue Pin and PWM Pin below.

Examples are added to show how to use this pin with setOutputMode().

PGO pin

Not tested.

PGO stands for Programming Option, it is used to calibrate / program the sensor. As the sensor can be programmed only a few times one should use this functionality with extreme care. See datasheet for a detailed list of steps to be done.

See Make configuration persistent below.

Hardware connection

The I2C address of the AS5600 is always 0x36.

The AS5600 datasheet states it supports Fast-Mode == 400 KHz and Fast-Mode-Plus == 1000 KHz.

The sensor should connect the I2C lines SDA and SCL and the VCC and GND to communicate with the processor. The DIR (direction) pin of the sensor should be connected to:

• GND = fixed clockwise(*)
• VCC = fixed counter clock wise
• a free IO pin of the processor = under library control.

In the latter setup the library can control the direction of counting by initializing this pin in begin(directionPin), followed by setDirection(direction). For the direction the library defines two constants named:

• AS5600_CLOCK_WISE (0)
• AS5600_COUNTERCLOCK_WISE (1)

(*) if begin() is called without directionPin or with this parameter set to 255, software direction control is enabled.

See Software Direction Control below for more information.

Interface

Constants

Most important are:

//  setDirection
const uint8_t AS5600_CLOCK_WISE         = 0;  //  LOW
const uint8_t AS5600_COUNTERCLOCK_WISE  = 1;  //  HIGH

//  0.087890625;
const float   AS5600_RAW_TO_DEGREES     = 360.0 / 4096;
//  0.00153398078788564122971808758949;
const float   AS5600_RAW_TO_RADIANS     = PI * 2.0 / 4096;

//  getAngularSpeed
const uint8_t AS5600_MODE_DEGREES       = 0;
const uint8_t AS5600_MODE_RADIANS       = 1;

See AS5600.h file (and datasheet) for all constants. Also Configuration bits below for configuration related ones.

Constructor + I2C

• AS5600(TwoWire *wire = &Wire) Constructor with optional Wire interface as parameter.
• bool begin(uint8_t directionPin = 255) set the value for the directionPin. If the pin is set to 255, the default value, there will be software direction control instead of hardware control. See below.
• bool begin(int sda, int scl, uint8_t directionPin = 255) idem, for the ESP32 where one can choose the I2C pins. If the pin is set to 255, the default value, there will be software direction control instead of hardware control. See below.
• bool isConnected() checks if the address 0x36 is on the I2C bus.
• uint8_t getAddress() returns the fixed device address 0x36.

Direction

To define in which way the sensor counts up.

• void setDirection(uint8_t direction = AS5600_CLOCK_WISE) idem.
• uint8_t getDirection() returns AS5600_CLOCK_WISE (0) or AS5600_COUNTERCLOCK_WISE (1).

Configuration registers

Please read the datasheet for details.

• bool setZPosition(uint16_t value) set start position for limited range. Value = 0..4095. Returns false if parameter is out of range.

• uint16_t getZPosition() get current start position.

• bool setMPosition(uint16_t value) set stop position for limited range. Value = 0..4095. Returns false if parameter is out of range.

• uint16_t getMPosition() get current stop position.

• bool setMaxAngle(uint16_t value) set limited range. Value = 0..4095. Returns false if parameter is out of range. See datasheet Angle Programming

• uint16_t getMaxAngle() get limited range.

• bool setConfigure(uint16_t value) Value = 0..0x4000 Returns false if parameter is out of range.

• uint16_t getConfigure()

Configuration bits

Please read datasheet for details.

Bit	short	Description	Values
0-1	PM	Power mode	00 = NOM, 01 = LPM1, 10 = LPM2, 11 = LPM3
2-3	HYST	Hysteresis	00 = OFF, 01 = 1 LSB, 10 = 2 LSB, 11 = 3 LSB
4-5	OUTS	Output Stage	00 = analog (0-100%), 01 = analog (10-90%), 10 = PWM
6-7	PWMF	PWM frequency	00 = 115, 01 = 230, 10 = 460, 11 = 920 (Hz)
8-9	SF	Slow Filter	00 = 16x, 01 = 8x, 10 = 4x, 11 = 2x
10-12	FTH	Fast Filter	Threshold 000 - 111 check datasheet
13	WD	Watch Dog	0 = OFF, 1 = ON
15-14		not used

The library has functions to address these fields directly.

• bool setPowerMode(uint8_t powerMode) returns false if parameter is out of range.
• uint8_t getPowerMode() returns the mode set.

See the .h file for the other get/set functions.

Hysteresis

• bool setHysteresis(uint8_t hysteresis) Suppresses "noise" on the output when the magnet is not moving. In a way one is trading precision for stability. returns false if parameter is out of range.

Read Angle

• uint16_t rawAngle() idem. returns 0 .. 4095. (12 bits) Conversion factor AS5600_RAW_TO_DEGREES = 360 / 4096 = 0.087890625 or use AS5600_RAW_TO_RADIANS if needed.
• uint16_t readAngle() read the angle from the sensor. This is the one most used.
• void setOffset(float degrees) sets an offset in degrees, e.g. to calibrate the sensor after mounting. Typical values are -359.99 - 359.99 probably smaller. Larger values will be mapped back to this interval. Be aware that larger values will affect / decrease the precision of the measurements as floats have only 7 significant digits. Verify this for your application.
• float getOffset() returns offset in degrees.

In #14 there is a discussion about setOffset(). A possible implementation is to ignore all values outside the -359.99 - 359.99 range. This would help to keep the precision high.

Angular Speed

• float getAngularSpeed(uint8_t mode = AS5600_MODE_DEGREES) is an experimental function that returns an approximation of the angular speed in rotations per second. The function needs to be called at least four times per rotation or once per second to get a reasonably precision.

• mode == AS5600_MODE_RADIANS (1): radians /second

• mode == AS5600_MODE_DEGREES (0): degrees /second (default)

• mode other => degrees /second

Negative values indicate reverse rotation. What that means depends on the setup of your project.

Note: the first call will return an erroneous value as it has no reference angle or time. Also if one stops calling this function for some time the first call after such delays will be incorrect.

Note: the frequency of calling this function of the sensor depends on the application. The faster the magnet rotates, the faster it may be called. Also if one wants to detect minute movements, calling it more often is the way to go.

Status registers

• uint8_t readStatus() see Status bits below.
• uint8_t readAGC() returns the Automatic Gain Control. 0..255 in 5V mode, 0..128 in 3V3 mode.
• uint16_t readMagnitude() reads the current internal magnitude. (page 9 datasheet) Scale is unclear, can be used as relative scale.
• bool detectMagnet() returns true if device sees a magnet.

Status bits

Please read datasheet for details.

Bit	short	Description	Values
0-2		not used
3	MH	overflow	1 = magnet too strong
4	ML	overflow	1 = magnet too weak
5	MD	magnet detect	1 = magnet detected
6-7		not used

Make configuration persistent.

USE AT OWN RISK

Please read datasheet twice.

The burn functions are used to make settings persistent. As these functions can only be called one or three times, they are highly permanent, therefore they are commented in the library.

The risk is that you make your as5600 USELESS.

USE AT OWN RISK

• uint8_t getZMCO() reads back how many times the ZPOS and MPOS registers are written to permanent memory. You can only burn a new Angle 3 times to the AS5600.
• void burnAngle() writes the ZPOS and MPOS registers to permanent memory. You can only burn a new Angle maximum THREE times to the AS5600.
• void burnSetting() writes the MANG register to permanent memory. You can write this only ONE time to the AS5600.

Software Direction Control

Experimental 0.2.0

Normally one controls the direction of the sensor by connecting the DIR pin to one of the available IO pins of the processor. This IO pin is set in the library as parameter of the begin(directionPin) function.

The directionPin is default set to 255, which defines a software direction control. To have this working one has to connect the DIR pin of the sensor to GND. This puts the sensor in a hardware clock wise mode, so it is up to the library to do the additional math so the readAngle() and rawAngle() behave as if the DIR pin was connected to the processor IO pin.

The gain is that the user does not need an IO pin for this, which makes connecting the sensor a bit easier.

The user still calls setDirection() as before to change the direction.

TODO: measure performance impact.

TODO: investigate impact on functionality of other registers.

Analogue OUT

(details datasheet - page 25)

The OUT pin can be configured with the function:

• bool setOutputMode(uint8_t outputMode)

When the analog OUT mode is set the OUT pin provides a voltage which is linear with the angle.

VDD	mode	percentage	output	1° in V
5V0	0	0 - 100%	0.0 - 5.0	0.01388889
5V0	1	10 - 90%	0.5 - 4.5	0.01111111
3V3	0	0 - 100%	0.0 - 3.3	0.00916667
3V3	1	10 - 90%	0.3 - 3.0	0.00750000

To measure these angles a 10 bit ADC or higher is needed.

When analog OUT is selected readAngle() will still return valid values.

PWM OUT

(details datasheet - page 27)

The OUT pin can be configured with the function:

• bool setOutputMode(uint8_t outputMode) outputMode = 2 = PWM

When the PWM OUT mode is set the OUT pin provides a duty cycle which is linear with the angle. However they PWM has a lead in (HIGH) and a lead out (LOW).

The pulse width is 4351 units, 128 high, 4095 angle, 128 low.

Angle	HIGH	LOW	HIGH %	LOW %	Notes
0	128	4223	2,94%	97,06%
10	242	4109	5,56%	94,44%
20	356	3996	8,17%	91,83%
45	640	3711	14,71%	85,29%
90	1152	3199	26,47%	73,53%
135	1664	2687	38,24%	61,76%
180	2176	2176	50,00%	50,00%
225	2687	1664	61,76%	38,24%
270	3199	1152	73,53%	26,47%
315	3711	640	85,29%	14,71%
360	4223	128	97,06%	2,94%	in fact 359.9 something as 360 == 0

Formula:

based upon the table above angle = map(dutyCycle, 2.94, 97.06, 0.0, 359.9);

or in code ..

t0 = micros();  // rising;
t1 = micros();  // falling;
t2 = micros();  // rising;  new t0

//  note that t2 - t0 should be a constant depending on frequency set.
//  however as there might be up to 5% variation it cannot be hard coded.
float dutyCycle = (1.0 * (t1 - t0)) / (t2 - t0);  
float angle     = (dutyCycle - 0.0294) * (359.9 / (0.9706 - 0.0294));

PWM frequency

The AS5600 allows one to set the PWM base frequency (~5%)

• bool setPWMFrequency(uint8_t pwmFreq)

mode	pwmFreq	step in us	1° in time
0	115 Hz	2.123	24.15
1	230 Hz	1.062	12.77
2	460 Hz	0.531	6.39
3	920 Hz	0.216	3.20

Note that at the higher frequencies the step size becomes smaller and smaller and it becomes harder to measure. You need a sub-micro second hardware timer to measure the pulse width with enough precision to get the max resolution.

When PWM OUT is selected readAngle() will still return valid values.

Multiplexing

The I2C address of the AS5600 is always 0x36.

To use more than one AS5600 on one I2C bus, one needs an I2C multiplexer, e.g. https://github.com/RobTillaart/TCA9548. Alternative could be the use of a AND port for the I2C clock line to prevent the sensor from listening to signals on the I2C bus.

Finally the sensor has an analogue output OUT. This output could be used to connect multiple sensors to different analogue ports of the processor.

Warning: If and how well this analog option works is not verified or tested.

Operational

The base functions are:

AS5600 as5600;

void setup()
{
  Serial.begin(115200);
  ...
  as5900.begin(4);     //  set the direction pin
  as5600.setDirection(AS5600_CLOCK_WISE);
  ...
}

void loop()
{
...
  Serial.println(as5600.readAngle());
  delay(1000);
...
}

See examples.

Future

Some ideas are kept here so they won't get lost. priority is relative

high prio

• get hardware to test.
• improve documentation.

med prio

• limit the setOffset() to -359.99 .. 359.99
• investigate readMagnitude()
  • combination of AGC and MD, ML and MH flags?
• investigate performance
  • basic performance per function
  • I2C improvements
  • software direction
• investigate OUT behavior in practice
  • analogue
  • PWM
• write examples:
  • as5600_calibration.ino (needs HW and lots of time)
  • different configuration options
• create changeLog.md

low prio

• add error handling
• investigate PGO programming pin.
• add mode parameter to offset functions.
  • see getAngularSpeed()