forder

I need to work on a project which requires a transmission of a signal consists of 16 bits. The 16 bits need to be transmitted via an RF module (only one RF transmitter and RF receiver). How do I transmit the signal thru the RF module?

I was thinking of using a 16 bit shift registers (parallel in/ serial out) at the beginning before the RF transmitter and also another 16 bit shift registers (serial in/ parallel out) at the receiving end of the RF module. But I find it very hard (extremely hard) to find a 16 bit shift register with serial in/ parallel out chip. I only manage to find a chip which is 74F675A (16 bit shift register with serial in/ parallel out) but it's very rare and most website don't sell them. If they sell, they sell it in large number.

Does this method good enough or is there any other way to perform the transmission?

Is there any other way to transmit the 16 bit signal? I cannot use any PLD or PIC microcontorllers.

Super_voip

Lucky you don't have to build a receiver as well, use 2 8bit and a counter to count to 8 (0-7) then use the second and count again

forder

I'm sorry if this is a silly question... but how do you tell the system which 8 bit is the first and which is the second 8 bit? The way i see your suggestion is that, use a counter to count until 8 bits then send the 8 bits to something. then the last 8 bits also are counted and sent to the next process.

The signal i need to transmit is continuous 16 bit signal, which means that after the current 16 bit signal, there is also other 16 bit signal coming, and there is also another 16 bit signal behind that. so one 16 bit signal contains one information.

Super_voip

The same way you would send 8bit info with start/stop bits, the two 8bit registers are loaded at the same then sent via serial. Can you use an UART?

philba

what is the source of the parallel data? if it's a microcontroller or computer, you can set it up to serialize the data and skip the par/ser converter.

mneary

You can wire 74HC165 and 74HC595 (8 bits each) in pairs as 16-bit P/S and S/P respectively.

How do you plan to synchronize them?

forder

the source of the parallel data is two A/D converters, each with 8 bits output... initially I planned to align each 8-bit output into a 16 bit shift register (parallel in / serial out) and transmit them thru RF and receive them in serial and store them in parallel..

can somebody please tell me how to implement UART?

or, like mr mneary mentioned, how do a pair of 74HC595 work since the 16 bits input comes in serial.. how do i separate the serial 16 bits into two 74HC595 S/P??

Nigel Goodwin

This is obviously a job for a PIC or other microcontroller, as you're not allowed to use them it's obviously a school/college assignment or project. You're supposed to do this yourself, other wise what is the point?.

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Papabravo

You use two eight bit shift registers the same way you would use a 16-bit shift register. The order of the data is which serial out you connect to which serial in. I'm surprised you can't see this.

forder

Don't say it like i don't want to do it myself. I wrote up there how i planned to do the job. That shows that I did figure something out (at least) and i've already started working on it.. it's just that I'm stuck in the middle of it and I'm wondering if i'm doing it right.. that's why i asked if there any other way to do it..

anyway thank you very much for pointing that out Mr Nigel Goodwin.. i get your point..

Sceadwian

Direction might not hurt, if anyone knows how to do this discretly, at least suggest a good direction to go in. He's not asking for answers, just clues =) I avoid discrete logic because of things like this, then again if it's for school I understand as well =)
The thing that really makes a UART besides parallel and shift generators is a baud generator (clock) the clock must be stable to work well.

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Cry_Wolf

Well i think, you should use two 8 bit shift registers in combination such that they act as a single 16 bit shift register. But remeber u must synchronyse both the shift registers on a common clock!

I think Thats the best way for you and may not be the simplest one

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kchriste

First read up asynchronous data communication:
http://en.wikipedia.org/wiki/Asynchr..._communication
Then read up on ways to modulate the RF transmitter, such as ASK and FSK:
http://en.wikipedia.org/wiki/Frequency-shift_keying
Then also realize that, to be reliable, you need some sort of error checking scheme. As this is a school project and you can't use a micro controller, you may be able to ignore any errors introduced by spotty RF signals.

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Gordz

Use two 74LS164's ( 8 bit serial in and parallel out) for the reciever and two 74LS165's ( 8 bit parallel in and serial out) for the transmiter. They are pretty straight forward and easily stacked, and of course not expensive. If you have pretty good filtering and you remember to always send 16 blanks first before the actual data stream you should be fine.