clock input

[ee04jjn]

hi, I am designing a simple as a project when the keyboard is pressed it would use a shift register to convert paralel to series and then I data will travel to reciever as a series and then it will get converted back to paralel and will send to 7 seament display but the problem is

how can I make the clock input exactly the same on transmitter part and reciever part
I cant use and dont want to use the same clock for both of them

thank you

 

[Nigel Goodwin]

hi, I am designing a simple as a project when the keyboard is pressed it would use a shift register to convert paralel to series and then I data will travel to reciever as a series and then it will get converted back to paralel and will send to 7 seament display but the problem is

how can I make the clock input exactly the same on transmitter part and reciever part
I cant use and dont want to use the same clock for both of them

You either use the same clock (syncronous) or no clock (asyncronous), RS232 is an asyncronous protocol - it uses a fixed speed with start and stop bits, so an 8 bit word takes 10 bits (usually!). The start bit syncronises the receiver at the beginning of every word, within the word the local oscillator needs to be accurate enough to read in each correct bit.

To do it in hardware you could use UART chips, if you can still get the really old ones? - or a PIC16F628 at either end would be a cheap easy solution, and offer more versatility.

 

[dalt]

You can use a phase locked loop to extract the exact clock from the bit stream that is transmitted. How accurate the clock extracted clock is will depend on thetype of encoding you use on your bit stream.

 

[Nigel Goodwin]

You can use a phase locked loop to extract the exact clock from the bit stream that is transmitted. How accurate the clock extracted clock is will depend on thetype of encoding you use on your bit stream.

That's one thing that Manchester coding is good for!.

 

[ee04jjn]

in simple term if I put I want 2 clock at the same pule
meaning at the same phase at all time no phase diffrence or lagging
is teher any microchip or simple circuit