GY-63_MS5611/libraries/GY521

GY521

Arduino library for I2C GY521 accelerometer-gyroscope sensor a.k.a. MCU-6050.

Description

Experimental library for GY521 a.k.a. MCU-6050.

Library is work in progress, in fact it is extracted and extended from an old project. It needs to be tested a lot more.

See changelog.md for latest updates.

0.5.0 Breaking change

Version 0.5.0 introduced a breaking change. You cannot set the 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 Wire pins before calling begin().

Examples

• GY521_angle read angleX, angleY, angleZ.
• GY521_performance_calibrate.ino determine calibration performance.
• GY521_performance measure performance.
• GY521_pitch_roll_yaw to get pitch roll yaw.
• GY521_raw_cooked make a table of raw measurements and derived data for analysis e.g. in a spreadsheet.
• GY521_readCalibration_1 read calibration values / errors for a "flat" sensor.
• GY521_readCalibration_2 generate calibration code snippet.
• GY521_test_1 test working of the sensor.
• GY521_test_2 test set/get functions (sort of unit test).
• GY521_two_sensors demo for two sensors.

Related

• https://invensense.tdk.com/wp-content/uploads/2015/02/MPU-6000-Datasheet1.pdf
• https://cdn.sparkfun.com/datasheets/Sensors/Accelerometers/RM-MPU-6000A.pdf register map.
• https://github.com/RobTillaart/Angle
• https://github.com/RobTillaart/AngleConverter

Breakout board

From left to right

pin	pinName	description	notes
0	VCC	+5V
1	GND	ground
2	SCL	I2C clock
3	SDA	I2C data
4	XDA	auxiliary data	see datasheet
5	XCL	auxiliary clock	see datasheet
6	AD0	address
7	INT	interrupt

Address

AD0 connected to GND => 0x68 AD0 connected to VCC => 0x69

Calibration (short version for now)

Since version 0.5.2 the library has a build in void calibrate(times) function which can be called instead of manual calibration. This function overwrites the values of axe aye aze gxe gye gze. calibrate() must be called after setAccelSensitivity(as) and setGyroSensitivity(gs).

Note the calibrate() function takes time, depending on the number of times.

Manual calibration

1. load and run calibration example
   it shows a header containing 6 numbers and 10 lines of 8 numbers
2. wait until the middle 6 of the longer lines stabilize (should all be 0)
3. copy the 6 numbers above the axe aye aze as these are the numbers needed.

Interface

#include "GY521.h"

Constructor

• GY521(uint8_t address = 0x69, , TwoWire *wire = &Wire) Constructor with default address. 0x68 is also a valid address. The wire argument is optional to select Wire1 Wire2 etc. on some boards.
• bool begin() Returns true if address can be found on I2C bus. Note call Wire.begin() before begin().
• bool isConnected() returns true if device can be found on I2C bus.
• void reset() set all internal values to 0 and throttle time to 10 ms.
• bool wakeUp() idem.

Calibrate

• void calibrate(uint16_t times) This function overwrites the values of axe aye aze gxe gye gze. To get "quality error" offsets, the GY521 sensor should not move during the calibration. The parameter times determines the number of measurements made. Typical values are 100 or more. Please note this is a time consuming function.

Ideal the function calibrate() should continue until it is stable (how to define) for n reads. Drawback is that this would make the duration unpredictable.

Throttle

• void setThrottle(bool throttle = true) throttle to force "delay" between reads.
• bool getThrottle() returns true if throttle mode is set.
• void setThrottleTime(uint16_t ti ) throttle time in milliseconds, max = 65535 = 1++ minute
• uint16_t getThrottleTime() returns throttle time set.

Read

Set before read

• bool setAccelSensitivity(uint8_t as) as = 0, 1, 2, 3 ==> 2g 4g 8g 16g
• uint8_t getAccelSensitivity() returns 0, 1, 2, 3
• bool setGyroSensitivity(uint8_t gs) gs = 0,1,2,3 ==> 250, 500, 1000, 2000 degrees/second
• uint8_t getGyroSensitivity() returns 0, 1, 2, 3
  = void setNormalize(bool normalize = true) normalizes pitch roll yaw or not. Default true. = bool getNormalize() returns flag.

Actual read

• int16_t read() reads all core measurements. returns status = GY521_OK on success.
• int16_t readAccel() read accelerometer only to speed up interaction. This call does update the throttle timer. returns status = GY521_OK on success.
• int16_t readGyro() read gyroscope only to speed up interaction. This call does update the throttle timer. returns status = GY521_OK on success. Note: for pitch roll yaw you need to call read().
• int16_t readTemperature() read temperature only, does not update the throttle timer. returns status = GY521_OK on success.
• uint32_t lastTime() last time sensor is actually read. In milliseconds. Not updated by readTemperature().

Since version 0.3.8 the read() and readGyro() function is updated to keep the range of getPitch(), getRoll() and getYaw() in the range 0..359.999 degrees. (Issue #36). Problem is that with continuous rotation in a same direction internal variables will overflow and new movements (angles) will get lost as insignificant digits.

In version 0.4.0 the normalization of pitch, roll and yaw is fixed and made conditional. (Issue #42).

Calls after read

Note that multiple calls will return the same value. One must explicitly call read() to get new values.

• float getAccelX() idem.
• float getAccelY() idem.
• float getAccelZ() idem.
• float getAngleX() idem.
• float getAngleY() idem.
• float getAngleZ() idem.
• float getTemperature() idem.
• float getGyroX() idem.
• float getGyroY() idem.
• float getGyroZ() idem.

Experimental Pitch Roll and Yaw

Pitch Roll and Yaw is work in progress and should not be used for projects yet.

• float getPitch() idem. May return any number. If setNormalize(true) return value will be 0-359.999
• float getRoll() idem. May return any number. If setNormalize(true) return value will be 0-359.999
• float getYaw() idem. May return any number. If setNormalize(true) return value will be 0-359.999

Register access

Read the register PDF for the specific value and meaning of registers.

• uint8_t setRegister(uint8_t reg, uint8_t value)
• uint8_t getRegister(uint8_t reg)

Documents

• check details registers - MPU-6000-Register-Map1.pdf

Error codes

Error code	value	notes
GY521_OK	0	not an error
GY521_THROTTLED	1	not an error
GY521_ERROR_READ	-1
GY521_ERROR_WRITE	-2
GY521_ERROR_NOT_CONNECTED	-3

Sensitivity Acceleration

unit g = gravity == 9.81 m/s^2

Acceleration	value	notes
2 g	0	default
4 g	1
8 g	2
16 g	3

Sensitivity Gyroscope

unit dps = degrees per second.

Gyroscope	value	notes
250 dps	0	default
500 dps	1
1000 dps	2
2000 dps	3

Operation

See examples, use with care.

Future

Must

• time
• improve documentation
• investigate Pitch Roll and Yaw math in detail.
  • investigate math needed.
  • implementation.
  • when?
• test test and test ...(ESP too)

Should

• test calibrate() function for different sensitivities.

Could

• add examples
• improve unit tests?
• reorder code in read(), would that save some micros.?
  • first all ax, then ay etc
  • footprint / performance gain?
• make enum for sensitivity Accel?
• make enum for sensitivity Gyro?

Wont

• look for maths optimizations (atan, hypot, performance)
  • ==> hypot optimized (fastTrig?)
  • other ideas affect accuracy, so unless new ideas arise.
• calibrate function in the lib
  • not as lib will grow too large.
• defaults value for functions?
  • user must set function parameters explicit

Support

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Thank you,