MPU-6050 Arduino libraries code archaeology

Wed, 19 Mar 2025 12:36:48 GMT

Compare and contrast getting normalized accelerometer values, where the raw value is -13248.00. (A.k.a. Please, make it make sense.)

Library 1; jarzebski's Arduino-MPU6050 - https://github.com/jarzebski/Arduino-MPU6050/
Library 2; Adafruit's Adafruit_MPU6050 - https://github.com/adafruit/Adafruit_MPU6050
Library 3; i2cdevlib/ElectronicCats' mpu6050 - https://github.com/ElectronicCats/mpu6050

Library 1;

( code )

Formula for normalized acceleration value at MPU6050_RANGE_2G;
raw * rangePerDigit * gravityConst
(raw * (1.0/16384)) * gravityConst
== (raw / 16384) * gravityConst
(-13248.00 * .000061) * 9.80665 = -7.92502845
== (-13248.00 / 16384) * 9.80665 = -7.92959589

Library 2;

( code )

Formula for normalized acceleration value at MPU6050_RANGE_2_G;
(raw / accel_scale) * gravityConst
(-13248.00 / 16384) * 9.80665 = -7.92959589

Library 3;

( code )

No normalized functions in MPU6050.cpp. Can use MotionApps files, but they go through Quaternions.
( code )

Formula for normalized acceleration value at MPU6050_ACCEL_FS_2;
// jarzebski way;
raw * accelerationResolution * gravityConst
-13248.00 * 0.000122 * 9.80665 = -15.850057

// adafruit way;
// (raw * (1.0/16384)) * gravityConst
// (raw * (2.0/16384)) * gravityConst
(-13248.00 / (2.0*16384)) * 9.80665 = -15.85919
((-13248.00*2.0) / 16384) * 9.80665 = -15.85919

Result is twice that of the others. accelerationResolution itself seems to be twice the others, so half it? Not sure if this is a mistake, or I'm missing something about MPU6050_ACCEL_FS_2 vs MPU6050_RANGE_2_G.
raw * (accelerationResolution/2) * gravityConst
-13248.00 * (accelerationResolution/2) * 9.80665 = -7.9250

accelerationResolution and get_acce_resolution() only exist in the ElectronicCats version, they're not accessible in the i2cdevlibs version. That version seems to really want you to use the Quaternion path. But you can always use the range values from the other versions yourself on the raw values.

comments

Busy hands | Disquiet mind

MPU-6050 Arduino libraries code archaeology

Library 1;

Library 2;

Library 3;