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DISTANCE = VELOCITY * TIME.16 km = 300,000 km/s * TIMETIME = 5.33333333 × 10 -7(thats 10 to the -7) secondsTIME = 0.533333333 microseconds or 533.333333 nanoseconds
You are limited to what ever the system clock rate is. If it is a 20MHz processor running at 20MHz, you have 5ns. That is pretty much max for any of the standard AVRS, I think. XMegas are reported to be spec'd for something like 32MHz.
not about keeping two systems in sync.
OPERATION: Transceiver A sends out a signal and starts a timer. Transceiver B receives A's signal and immediately replies with another signal. Transceiver A stops its timer once it receives the reply from B. Take the time , divide it by two and you have the time it took to go one way.
Quote from: GearMotion on April 10, 2009, 07:38:22 AMnot about keeping two systems in sync. they don't have to be in sync. Think about it... Quote from: airman00 on April 07, 2009, 10:37:56 AMOPERATION: Transceiver A sends out a signal and starts a timer. Transceiver B receives A's signal and immediately replies with another signal. Transceiver A stops its timer once it receives the reply from B. Take the time , divide it by two and you have the time it took to go one way. Transceiver B is constantly waiting and immediately sends a reply to the Transceiver A that receives , so Transceiver A and B do not have to be synced. Obviously you would have to subtract how long it takes to send out the RF signal out UART or whatever.....
RF signal out of a UART?? The point that is being made is you are talking about speed of light measurements using a $2 processor running at 20 MHz using a crystal with 200 parts per million accuracy. You have to account for the variability of a signal happening at any state of the processor operation. The AVR's variability makes this effort impractical.
But still ,from what I understand, I will be able to get my +-.1 mile (~.16 km) accuracy. What do you think GearMotion?
I think my idea is really doable!
So, in other words you didn't read the other quite recent threads we had on the subject??