Difference: MagicWandOld (11 vs. 12)

Revision 122022-06-25 - UliRaich

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The Magic Wand Example

Introduction

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The magic wand example shows how to detect gestures using an accelerometer. Different types of accelerometers are easily available:

The ADXL345 is a tree axis digital accelerometer by Analog Devices
I wrote a pure MircoPython driver for the ADXL345 available at https://github.com/uraich/IoT-Course/tree/master/exercises/solutions/exercise_16/adxl345.
The MPU6050 is a six axis device (Gyro and Accelerometer) from Ivensense. It is described by its datasheet and the register description document.
Jeff Rowberg has written a very complete MPU6050 driver for the Arduino in C++, which includes access to its Digital Motion Processor, whose description cannot be found anywhere on the WEB. I ported this driver to MicroPython together with a few example programs drafted after Jeff's C++ examples: https://github.com/uraich/IoT-Course/tree/master/exercises/solutions/exercise_16/mpu6050.

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The MPU9250 is very similar to he MPU6050 but has a magnetometer in addition. Here is its data sheet and the register map. The MPU92/66 has the necessary pins to be accessed either through I2C or SPI.

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The MPU9250 is very similar to he MPU6050 but has a magnetometer in addition. Here is its data sheet and the register map. The MPU9250/6500 has the necessary pins to be accessed either through I2C or SPI.
Attention: I bought an "MPU9250" board marked MPU92.65 with a chip marked MP92. This chip is either only a MPU6500 or it is faulty. It is probably a fake. I never managed to access the AK8963 magnetometer, which is part of a real MPU9250.

The MPU6050 and the MPU9250 gave hardware offset registers which allow calibrating the device. When the device is horizontally mounted and stationary (not moving) we expect the values:

0,0,1g for the measured acceleration in x, y and z, z pointing in the direction of gravity.
and 0,0,0 for the gyroscope

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