TIMER1 or RCTIME?

[Acetronics2]

amount of time it takes from sending the signal to receiving the signal. As many of you know, we need the elapsed time in order to calculate the distance from the object. I've been trying to read up on both the TIMER registers and the RCTIME command as possibilities for helping us fix this problem but as of yet I've really gotten no where. If any of you could provide us with a sample code to go by we would greatly appreciate it. Thank you all for your time.

Hi, ...

Let's see:

sound speed @ 20°C ( SQR ( 1.4*287*(273+20)) = ~ 340 m/s

say your min distance will be ~ 10 cm ... time will be 2x.1/340 ~ 600 µS

RCTime @ 20 Mhz gives 2µS granularity ... for a 16 bits value

so, the range will be 10 cm to 10cm* 65535/300 = 21.8 meters.

Looks fine ...

Alain