i aplogize for my stupidity that i should include the image. here btw. i assume this is hardware problem since the code, which is a very plain sample code from adafruit, is running when uploading. i was thinking maybe the arrangement of rx, tx, vin, gnds are not the same in my model? i cant be sure of that though.
just to give it a shot, i wonder which should be the Rx, Tx, GND, VIN here? my shop i ordered didnt include a manual of this sensor's configuration pins.