Arduino library for AS5600 and AS5600L magnetic rotation meter.
AS5600 is a library for an AS5600 / AS5600L based magnetic rotation meter. More exact, it measures the angle (rotation w.r.t. reference) and not RPM. Multiple angle measurements allows one to calculate or estimate the RPM.
The AS5600 and AS5600L sensors are pin compatible (always check your model's datasheet).
Warning: experimental
The sensor can measure a full rotation in 4096 steps. The precision of the position is therefore limited to approx 0.1°. Noise levels are unknown, but one might expect that the sensor is affected 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.
Please share your experiences.
Version 0.6.2 fixes bugs that might affect your code.
- fix getCumulativePosition() to make it direction aware.
- fix negative values in getRevolutions().
- fix setOffset() to not set offset to 360 degrees.
- fix #66, make I2C functions virtual.
Version 0.5.0 introduced a breaking change. You cannot set the SDA and SCL pins in begin() any more. This reduces the dependency of processor dependent Wire implementations. The user has to call Wire.begin() and can optionally set the I2C pins before calling AS5600.begin().
- https://github.com/RobTillaart/Angle
- https://github.com/RobTillaart/AngleConvertor
- https://github.com/RobTillaart/AverageAngle
- https://github.com/RobTillaart/runningAngle
The I2C address of the AS5600 is always 0x36.
The sensor should connect the I2C lines SDA and SCL and the VCC and GND to communicate with the processor. Do not forget to add the pull up resistors to improve the I2C signals.
The AS5600 datasheet states it supports Fast-Mode == 400 KHz and Fast-Mode-Plus == 1000 KHz.
I2C performance tests with an AS5600L with an UNO failed at 400 KHz. After investigation it became clear that pull ups are mandatory. The UNO expects 5 Volt I2C signals from the AS5600. However the device only provides 3V3 pulses on the bus. So the signal was not stable fast enough (not "square enough"). After applying pull ups the AS5600L worked up to 1000 KHz.
From datasheet, page 30 - Direction (clockwise vs. counter-clockwise)
The AS5600 allows controlling the direction of the magnet rotation with the DIR pin. If DIR is connected to GND (DIR = 0) a clockwise rotation viewed from the top will generate an increment of the calculated angle. If the DIR pin is connected to VDD (DIR = 1) an increment of the calculated angle will happen with counter-clockwise rotation.
This AS5600 library offers a 3rd option for the DIR (direction) pin of the sensor:
- Connect to GND ==> fixed clockwise(*). This is the default.
- Connect to VCC ==> fixed counter-clockwise.
- Connect to an IO pin of the processor == Hardware Direction Control by library.
In the 3rd configuration the library controls the direction of counting by initializing this pin in begin(directionPin), followed by setDirection(direction). For the parameter 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.
The sensor has an output pin named OUT. This pin can be used for an analogue or PWM output signal (AS5600), and only for PWM by the AS5600L.
See Analogue Pin and PWM Pin below.
Examples are added to show how to use this pin with setOutputMode().
See more in the sections Analog OUT and PWM OUT below.
Some AS5600 modules seem to have a resistor between PGO and GND. This causes the AS5600 to disable the output (to use it for programming, see datasheet). This resistor needs to be removed to use the OUT pin.
Not tested. ==> Read the datasheet!
PGO stands for ProGramming Option, it is used to calibrate and 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.
The I2C address of the AS5600 is always 0x36.
| sensor | address | changeable |
|---|---|---|
| AS5600 | 0x36 | NO |
| AS5600L | 0x40 | YES, check setAddress() |
To use more than one AS5600 on one I2C bus, see Multiplexing below.
The AS5600L supports the change of I2C address, optionally permanent. Check the setAddress() function for non-permanent change.
Sometimes you need to control more devices than possible with the default address range the device provides. This is possible with an I2C multiplexer e.g. TCA9548 which creates up to eight channels (think of it as I2C subnets) which can use the complete address range of the device.
Drawback of using a multiplexer is that it takes more administration in your code e.g. which device is on which channel. This will slow down the access, which must be taken into account when deciding which devices are on which channel. Also note that switching between channels will slow down other devices too if they are behind the multiplexer.
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.
| board | sensor | results | notes |
|---|---|---|---|
| Arduino UNO | AS5600 | up to 900 KHz. | #22 |
| Arduino UNO | AS5600L | up to 300 KHz. | |
| ESP32 | AS5600 | no data | |
| ESP32 | AS5600L | up to 800 KHz |
No other boards tested yet.
When polling the AS5600 with an ESP32 to measure RPM an issue has been reported. See #28
The problem is that the ESP32 can be blocking for up to one second if there is a problem in the connection with the sensor. Using setWireTimeout() does not seem to solve the problem (2023-01-31). In the issue the goal was to measure the turns of a rotating device at around 3800 RPM.
3800 RPM == 64 rounds / second.
To measure speed one need at least 3 angle measurements per rotation. This results in at least 192 measurements per second which is about 1 per 5 milliseconds.
Given that the ESP32 can block for a second, it can not be guaranteed to be up to date. Not for speed, but also not for total number of rotations.
#include "AS5600.h"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;
// 4.06901041666666e-6
const float AS5600_RAW_TO_RPM = 1.0 / 4096 / 60;
// getAngularSpeed
const uint8_t AS5600_MODE_DEGREES = 0;
const uint8_t AS5600_MODE_RADIANS = 1;
const uint8_t AS5600_MODE_RPM = 2;See AS5600.h file (and datasheet) for all constants. Also Configuration bits below for configuration related ones.
- AS5600(TwoWire *wire = &Wire) Constructor with optional Wire interface as parameter.
- bool begin(uint8_t directionPin = AS5600_SW_DIRECTION_PIN) set the value for the directionPin. If the pin is set to AS5600_SW_DIRECTION_PIN, the default value, there will be software direction control instead of hardware control. See below.
- bool isConnected() checks if the address 0x36 (AS5600) is on the I2C bus.
- uint8_t getAddress() returns the fixed device address 0x36 (AS5600).
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).
See Software Direction Control below for more information.
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.
Please read datasheet for details.
- bool setConfigure(uint16_t value) value == 0..0x3FFF Access the register as bit mask. Returns false if parameter is out of range.
- uint16_t getConfigure() returns the current configuration register a bit mask.
| 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.
The setters() returns false if parameter is out of range.
- bool setPowerMode(uint8_t powerMode)
- uint8_t getPowerMode()
- 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.
- uint8_t getHysteresis()
- bool setOutputMode(uint8_t outputMode)
- uint8_t getOutputMode()
- bool setPWMFrequency(uint8_t pwmFreq)
- uint8_t getPWMFrequency()
- bool setSlowFilter(uint8_t mask)
- uint8_t getSlowFilter()
- bool setFastFilter(uint8_t mask)
- uint8_t getFastFilter()
- bool setWatchDog(uint8_t mask)
- uint8_t getWatchDog()
- uint16_t rawAngle() 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() returns 0 .. 4095. (12 bits) Conversion factor AS5600_RAW_TO_DEGREES = 360 / 4096 = 0.087890625 or use AS5600_RAW_TO_RADIANS if needed. The value of this register can be affected by the configuration bits above. This is the one most used.
- bool setOffset(float degrees) overwrites the existing offset. It 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. Returns false if degrees > 360000.
- float getOffset() returns offset in degrees.
- bool increaseOffset(float degrees) adds degrees to the existing offset. If setOffset(20) is called first and increaseOffset(-30) thereafter the new offset is -10 degrees. Returns false if degrees > 360000.
In issue #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. User responsibility.
In #51 increaseOffset is discussed.
// offset == 0;
as.setOffset(20);
// offset == 20;
as.setOffset(-30);
// offset = -30;
// versus
// offset == 0;
as.setOffset(20);
// offset == 20;
as.increaseOffset(-30);
// offset = -10;- float getAngularSpeed(uint8_t mode = AS5600_MODE_DEGREES, bool update = true) is an experimental function that returns an approximation of the angular speed in rotations per second.
If update is false, the function will use the last read value of readAngle(). This is also used by getCumulativePosition() and when used both these functions a substantial performance gain is made. See example AS5600_position_speed.ino.
In case of a reading failure (when update == true), the function can return NAN.
The function needs to be called at least four times per rotation or once per second to get a reasonably precision.
| mode | value | description | notes |
|---|---|---|---|
| AS5600_MODE_RADIANS | 1 | radians /sec | |
| AS5600_MODE_DEGREES | 0 | degrees /sec | default |
| other | - | degrees /sec |
Negative return values indicate reverse rotation. What that exactly 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.
An alternative implementation is possible in which the angle is measured twice with a short interval. The only limitation then is that both measurements should be within 180° = half a rotation.
Since 0.3.3 an experimental cumulative position can be requested from the library. The sensor does not provide interrupts to indicate a movement or revolution Therefore one has to poll the sensor at a frequency at least three times per revolution with getCumulativePosition()
The cumulative position (32 bits) consists of 3 parts
| bit | meaning | notes |
|---|---|---|
| 31 | sign | typical + == CW, - == CCW |
| 30-12 | revolutions | |
| 11-00 | raw angle | call getCumulativePosition() |
Functions are:
- int32_t getCumulativePosition(bool update = true) reads sensor and updates cumulative position.
Updated in 0.6.2 to follow the setting of the directionPin. If update is false, the function will use the last read value of readAngle(). This is also used by getCumulativePosition() and when used both these functions a substantial performance gain is made. See example AS5600_position_speed.ino. - int32_t getRevolutions() converts last position to whole revolutions. Convenience function. Updated in 0.6.2 to return zero for the first negative revolution as this is more correct as there is not yet a negative turn made. This might be breaking behavior.
- int32_t resetPosition(int32_t position = 0) resets the "revolutions" to position (default 0). It does not reset the delta (rotation) since last call to getCumulativePosition(). Returns last position (before reset).
- int32_t resetCumulativePosition(int32_t position = 0) completely resets the cumulative counter. This includes the delta (rotation) since last call to getCumulativePosition(). Returns last position (before reset).
As this code is experimental, names might change in the future. As the function are mostly about counting revolutions the current thoughts for new names are:
int32_t updateRevolutions(); // replaces getCumulativePosition();
int32_t getRevolutions();
int32_t resetRevolutions(); // replaces resetPosition();Since 0.6.4 it is possible to optimize the performance of getting both.
- getCumulativePosition()
- getAngularSpeed()
As both use to read the Angle, one can reuse this by setting the update flag to false. One must call readAngle() right before both of them In code:
...
alpha = as5600.readAngle();
pos = as5600.getCumulativePosition(false);
speed = as5600.getAngularSpeed(AS5600_MODE_DEGREES, false);
// process the values...Please note that the mode parameter for getAngularSpeed() becomes mandatory.
The call to readAngle() caches the angle read and uses it in both functions. The savings are substantial, see AS5600_position_speed.ino
The advantage is that both speed and pos are based upon the same reading. A disadvantage is that the latter of the two calls is not max up to date.
Use with care.
- 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.
- bool magnetTooStrong() idem.
- bool magnetTooWeak() idem.
Please read datasheet for details.
| Bit | short | Description | Values |
|---|---|---|---|
| 0-2 | not used | ||
| 3 | MH | overflow | 1 = magnet too strong |
| 4 | ML | underflow | 1 = magnet too weak |
| 5 | MD | magnet detect | 1 = magnet detected |
| 6-7 | not used |
Since 0.5.2 the library has added experimental error handling. For now only lowest level I2C errors are checked for transmission errors. Error handling might be improved upon in the future.
Note: The public functions do not act on error conditions. This might change in the future. So the user should check for error conditions.
int e = lastError();
if (e != AS5600_OK)
{
// handle error
}- int lastError() returns the last error code. After reading the error status is cleared to AS5600_OK.
| Error codes | value | notes |
|---|---|---|
| AS5600_OK | 0 | default |
| AS5600_ERROR_I2C_READ_0 | -100 | |
| AS5600_ERROR_I2C_READ_1 | -101 | |
| AS5600_ERROR_I2C_READ_2 | -102 | |
| AS5600_ERROR_I2C_READ_3 | -103 | |
| AS5600_ERROR_I2C_WRITE_0 | -200 | |
| AS5600_ERROR_I2C_WRITE_1 | -201 |
- 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, and only 2 times for the AS5600L. This function is safe as it is readonly.
The burn functions are used to make settings persistent. These burn functions are permanent, therefore they are commented in the library. Please read datasheet twice, before uncomment them.
USE AT OWN RISK
Please read datasheet twice as these changes are not reversible.
The risk is that you make your AS5600 / AS5600L USELESS.
USE AT OWN RISK
These are the two "unsafe" functions:
- void burnAngle() writes the ZPOS and MPOS registers to permanent memory. You can only burn a new Angle maximum THREE times to the AS5600 and TWO times for the AS5600L.
- void burnSetting() writes the MANG register to permanent memory. You can write this only ONE time to the AS5600.
Some discussion about burning see issue #38
(I have no hands on experience with this functions)
USE AT OWN RISK
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 clockwise mode. Then 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 a processor IO pin.
The user still calls setDirection() as before to change the direction of the increments and decrements.
The advantage is one does not need that extra IO pin from the processor. This makes connecting the sensor a bit easier.
TODO: measure performance impact.
TODO: investigate impact on functionality of other registers.
(details datasheet - page 25 = AS5600)
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.
The AS5600L does NOT support analog OUT. Both mode 0 and 1 will set the OUT pin to VDD (+5V0 or 3V3).
(details datasheet - page 27 = AS5600)
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 |
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));
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.
- AS5600L(uint8_t address = 0x40, TwoWire *wire = &Wire) constructor. As the I2C address can be changed in the AS5600L, the address is a parameter of the constructor. This is a difference with the AS5600 constructor.
- bool setAddress(uint8_t address) Returns false if the I2C address is not in valid range (8-119).
UPDT = update page 30 - AS5600L
- bool setI2CUPDT(uint8_t value)
- uint8_t getI2CUPDT()
These functions seems to have only a function in relation to setAddress() so possibly obsolete in the future. If you got other insights on these functions please let me know.
The base functions are:
AS5600 as5600;
void setup()
{
Serial.begin(115200);
...
as5600.begin(4); // set the direction pin
as5600.setDirection(AS5600_CLOCK_WISE);
...
}
void loop()
{
...
Serial.println(as5600.readAngle());
delay(1000);
...
}See examples.
Some ideas are kept here so they won't get lost. priority is relative.
- re-organize readme.md
- rename revolution functions
- to what?
- Implement extended error handling in public functions.
- will increase footprint !! how much?
- call writeReg() only if readReg() is OK ==> prevent incorrect writes
if (_error != 0) return false;- idem readReg2()
- set AS5600_ERROR_PARAMETER e.g. setZPosition()
- a derived class with extended error handling?
- investigate readMagnitude()
- combination of AGC and MD, ML and MH flags?
- investigate OUT behaviour in practice
- analogue
- PWM
- need AS5600 on breakout with support
- check / verify Power-up time
- 1 minute (need HW)
- check Timing Characteristics (datasheet)
- is there improvement possible.
- investigate PGO programming pin.
- check for compatible devices
- AS5200 ?
- investigate performance
- basic performance per function
- I2C improvements
- software direction
- write examples:
- as5600_calibration.ino (needs HW and lots of time)
- different configuration options
- fix for AS5600L as it does not support analog OUT.
- type field?
- other class hierarchy?
- base class with commonalities?
- ==> just ignore for now.
- add mode parameter to offset functions.
- see getAngularSpeed()
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