Information

I2C ADDRESS

• ADXL345 : 0x53
• ITG3200 : 0x68

Data Sheet

• http://www.analog.com/jp/mems-sensors/mems-inertial-sensors/adxl345/products/product.html

calibration data

• double a_xdata_Plus = 266.00;
• double a_xdata_Minus = -262.50;
• double a_ydata_Plus = 282.50;
• double a_ydata_Minus = -246.00;
• double a_zdata_Plus = 250.00;
• double a_zdata_Minus = -259.00;

Offset

• a_xOffset = 0.5 * (a_xdata_Plus + a_xdata_Minus) = 1.75
• a_yOffset = 0.5 * (a_ydata_Plus + a_ydata_Minus) =18.25
• a_zOffset = 0.5 * (a_zdata_Plus + a_zdata_Minus) = -4.5

Gain

• a_xGain = 0.5 * (a_xdata_Plus - a_xdata_Minus) / 255 = 1.04
• a_yGain = 0.5 * (a_ydata_Plus - a_ydata_Minus) / 255 = 1.04
• a_zGain = 0.5 * (a_zdata_Plus - a_zdata_Minus) / 255 = 1.00

Sampling

• a_x = (((a_xAccumulator / SAMPLES) - a_xOffset) / a_xGain);
• a_y = (((a_yAccumulator / SAMPLES) - a_yOffset) / a_yGain);
• a_z = (((a_zAccumulator / SAMPLES) - a_zOffset) / a_zGain);

Angle

• #define ACCELEROMETER_ANGLE_GAIN (90.0 / 255.0)
• x = (a_x - a_xBias) * ACCELEROMETER_ANGLE_GAIN;
• y = (a_y - a_yBias) * ACCELEROMETER_ANGLE_GAIN;
• z = (a_z - a_zBias) * ACCELEROMETER_ANGLE_GAIN;

Angle

• hdgV = atan2(a_x, a_z); Down 0 -> 1.5 -> 3.14 / Up 0 -> -1.5 -> -3.14
• hdgV = atan2(a_x, a_z) * 180/3.14159; Down 0 -> 90 -> 180 / Up 0 -> -90 -> -180
• angle_z = angle_z / cos(hdgV);