Serial Data Transmition

[Victor Frankenstein]

How are series of bits differentiated in serial data transfer for example
0101 & 1101, in a remote control car, how and what are syncronization pulses interpreted by the recever ? for example

0101 and 4 longer 1's 1101 4 long 1's :?:

 

[Nigel Goodwin]

How are series of bits differentiated in serial data transfer for example
0101 & 1101, in a remote control car, how and what are syncronization pulses interpreted by the recever ? for example

0101 and 4 longer 1's 1101 4 long 1's :?:

It depends completely on the protocol used, but radio control doesn't normally use digital coding in this way - it simply uses pulse width coding and feeds the servos directly.

 

[Victor Frankenstein]

Nigel Goodwin wrote:
It depends completely on the protocol used, but radio control doesn't normally use digital coding in this way - it simply uses pulse width coding and feeds the servos directly.

I never thought of that, how are the pulse widths interpreted ?

Consider one 3ms pulse and another 6ms pulse, how would a radio receiver interpret the different pulse widths ?

 

[Nigel Goodwin]

Nigel Goodwin wrote:
It depends completely on the protocol used, but radio control doesn't normally use digital coding in this way - it simply uses pulse width coding and feeds the servos directly.

I never thought of that, how are the pulse widths interpreted ?

Consider one 3ms pulse and another 6ms pulse, how would a radio receiver interpret the different pulse widths ?

For standard radio control systems the pulses vary from 1mS to 2mS, and these pulses are fed directly into the servos. Servos are specifically designed to operate from these width pulses, and everything is done inside the servo. The receiver itself doesn't interpret them, it simply splits them up, and sends one pulse to each servo.

If you want to use it for something else, you can simply measure the width of the pulse, giving a numeric value representing the pulse width. It's common to use a PIC for this!, and there are a great many designs out there that you can download. The UK magazine EPE recently published one such design, using a PIC to give a switched output from a radio control channel.