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5v on trig at power up

I was confused why when first powered up and not attached to the BBB, the hcsr04 has 5v on trig. Further, I was reluctant to connect this pin directly to the BBB, as there are warnings dissuading this behavior on a default 3.3v board.

I found that the sonar works (just as well? better?) with the trig pin at 2.3v. I used a voltage divider ( 1k and 10k resistors ) to accomplished this.

I have 6 of these hcsr04 sonars from 2 different sources, and they all behave the same way. Does anyone else experience different behavior?