You haven't stated the range of distances you're attempting to measure. The speed of light table below is from Wikipedia and will help put things in perspective.
Light will travel 1 meter in ~3.3 nano-seconds – 3.3 x 10^-9 seconds. So to measure 1 meter, you must transmit a pulse, respond to the pulse with the receiving end to transmit a return pulse in some fixed, known time, sense the received pulse and measure Δt with nano-second resolution.
A microprocessor running at 20 MHz has a clock cycle of 5 x 10^-8 seconds....
Looks like a problem.
The speed of sound in air is 343 meters/second, roughly a million times slower than the speed of light. A bit more practical to measure I should think.
Light will travel 1 meter in ~3.3 nano-seconds – 3.3 x 10^-9 seconds. So to measure 1 meter, you must transmit a pulse, respond to the pulse with the receiving end to transmit a return pulse in some fixed, known time, sense the received pulse and measure Δt with nano-second resolution.
A microprocessor running at 20 MHz has a clock cycle of 5 x 10^-8 seconds....
Looks like a problem.
The speed of sound in air is 343 meters/second, roughly a million times slower than the speed of light. A bit more practical to measure I should think.