Reading sensor value from arduino and use it in opencv

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Hi all.... I do a project where i need to find distance between objects of various shapes and camera... I tried applying the method i found here ... but it requires my object to be in fixed orientation and width.. So I am thinking of using ultrasonic sensor to do the distance finding and communicate it with opencv serially using arduino.. but the problem is as i am new to opencv, i couldn't find any leads on how to read data serially in opencv... I could be extremely thankful if someone could help me.. i need it asap so badly...!!!