diode isolation - is this ok?

i'm using a parallax ping distance sensor which has a single signal pin. You pulse it high for 5-15 us then turn and listen for IT to pulse the same line high for a length of time corresponding to the distance. http://profesores.fi-b.unam.mx/m3615m/datasheet-sen136b5b.pdf

I'm using an mcu with dedicated input and output pins so i can't quite do that. I'm planning to compensate with the circuit above, sending the pulse out on one pin and reading the response on another. The trigger output from the MCU is sent high for 15 us then the MCU lowers it to 0. The resistor pulls the pin down to 0 but the the ping sensor should be able to overcome it and the diode should stop the MCU's 0 from interfering.

This looked ok on the scope except the high pulse from the MCU was down to about 3.3v by the time it got to the sensor - the response pulse looked fine and fat at near 5v.

I thought all was fine til the sensor stopped working. Trying a spare, it's fine so it looks like I borked the first one.

Does this circuit seem safe?

Actually, just a 1K or 2.2K series-R will probably work.

Actually, just a 1K or 2.2K series-R will probably work.

thanks - i bet it would, certainly my circuit is not much different from a 22k.