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Using the cheap HC-SR04 ultrasonic sensor and an arduino nano we can build a low cost sensor array for robotics. The arduino code will poll all the sensors and send byte packets via serial interface with the index and the distance to a Python app to process.

For measuring the distances we use a sonar technique to calculate the time of flight of the sound. The HC-SR04 is very inaccurate for distance measurement but can be used as a cheap low level fail-safe system for proximity object detection in order to avoid hitting obstacles during navigation.

sensor_index is a one byte unsigned integer like uint8_t

sensor_reading is a two byte unsigned integer line unsigend int