Acceleration sensor module with attitude determining function

An acceleration sensor module with an attitude determining function, comprising:

• a three-axis acceleration sensor configured to detect accelerations in X-axis, Y-axis, and Z-axis directions that are perpendicular to each other;
• an X-axis acceleration level determining section configured to determine whether an X-axis acceleration signal output from the three-axis acceleration sensor has a value equal to or more than a predetermined positive threshold level, a value equal to or less than a predetermined negative threshold level, a value between the positive threshold level and a level of 0, or a value between the level of 0 and the negative threshold level;
• a Y-axis acceleration level determining section configured to determine whether a Y-axis acceleration signal output from the three-axis acceleration sensor has a value equal to or more than a predetermined positive threshold level, a value equal to or less than a predetermined negative threshold level, a value between the positive threshold level and a level of 0, or a value between the level of 0 and the negative threshold level;
• and
• an attitude determining section configured to determine a rotated attitude of a device equipped with the acceleration sensor with respect to the Z-axis direction based on results of determinations made by the X-axis acceleration level determining section and the Y-axis acceleration level determining section, wherein:
• the three-axis acceleration sensor, the X-axis acceleration level determining section, the Y-axis acceleration level determining section, and the attitude determining section are formed as a single unit;
• the X-axis acceleration level determining section and the Y-axis acceleration level determining section each output the determination result as a 2-bit value, and the attitude determining section outputs the determined attitude as a 2-bit value;
• and
• the attitude determining section determines a current attitude based on a combination of the 2-bit value indicating a preceding determined attitude, the 2-bit value output from the X-axis acceleration level determining section, and the 2-bit value output from the Y-axis acceleration level determining section.