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the red line not moving
yes my sensor is moving smoothly. when i change my port it didn't work
1. First common error that stops the processing program is the device not found error (in simple words)the symptoms are that the line with 'com4' would be highlighted red. the solution is to change the com4 to that port where your arduino is connected.
isn't the part of sensor correct to part?, i use sensor SRF-08