# convert...

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#### bogdanfirst

##### New Member
well, basicly, i need to convert the 8 bits of a paralel port to 4 or less bits, then send the data to a 4 channel transmitter/receiver i got from a radiu controlled car and then decode back to 8 bits.
i think i will need some multiplexers/demultiplexers. :?: :!:
i got some 64153, 74251 and other decoder ics. please can anyone tell me how to build this, i am not so sure.(also the circuits could use some other ICs.
also, i have another question, 74164 serial to paralel converter. can i use this to convert from the serial port of the computer to 8 bit paralel? :?:
anybody got any schematics?

#### kinjalgp

##### Active Member
You can use 8 line to 4 line multiplexer IC 74157.
Regarding conversion of serial port data to parallel, it cannot be ahieved using 74164, you'll require a special time-synchronised (according to baud rates) converter. One other reason is also that serial ports send start and stop bits along with data bits which will be wrongly interpreted by 74164 as data bits. You can serach the net for PIC16F84 or 89C2051 based serial to parallel converters. I had found some while surfing.

#### bogdanfirst

##### New Member
ok, thanks.
i know about pics, but the cheapaest i could find here, 16F84 is around $10, so it is quite expensive and a programmer with some soft is more than$100, so threre is no posibility about this.
but here is about the converter. i use 74157 for encoding, but what do i use for decoding?
and also dont i need a clock line or something?
i only got a receiver-transmitter with 4 channele each can be H or L

#### kinjalgp

##### Active Member
I don't have any idea about the demultiplexer for 74157. You'll have to build on your own using discrete ICs and gates. But doing this thing will require a synchronization between transmitter and receiver which is not possible without use of either sync. pulses or some other method. So a better thing would be to use specially desined Tx Rx ICs from Holtek Semiconductors which are readily available. Some of tge members of this family are HT12D and HT12E or HT600 etc.

#### bogdanfirst

##### New Member
yes, but it is quite hard to build radio circuits, even though i only need some descrete components apart of the ics.
but what about other pair of multiplexer/demultiplexer, maybe convert from 6 to 3 bits and use another bit for sincronization....?

#### kinjalgp

##### Active Member
Yeah that can be done but I still doubt about its flaw-less functionality. You'll have tough time getting both Tx and Rx synchronised even though you use one bit as sync. bit. Since this bit is no different from other bits if you start the Tx and Rx at different times, the one of the data bit may also be wrongly interpreted as sync. bit.
I hope you are getting what I am trying to say.

#### bogdanfirst

##### New Member
what i am thikink is to generate a sinc signal and control the multiplexer then send that bit trough the radio and use it as a sinc bit for the demultiplexer.
and anyway, do you know any pair of multiplexers/demultiplexers i can use?
8 to 4, 6 to 3 anything, ill choose the best way.
thanks for yout time.
and have a happy women's day :lol:
just joking.

#### kinjalgp

##### Active Member
bogdanfirst said:
and have a happy women's day :lol:
just joking.
:lol: Let them enjoy this single day rest 364 are ours :wink: :lol:

Jokes apart, let me do some search on mux-demux pairs.

ok, thanks.

#### mechie

##### New Member
Parallel to serial

Why not use the good old 6402 UART ?
8 bits -to- serial (single transmitter channel).
Serial back to parallel with a second 6402.
You can add start and stop bits if you wish (easy wire links)
Choose a baud rate that suits your RC gear.

The worst error you can have (ignoring total radio failure) will be a single 8 bit byte as each is independantly coded, transmitted and (if you wish)parity checked.

#### bogdanfirst

##### New Member
yes, i thought of that in the first time.
the problem is that i cant find one to buy here.
what letters does it have before and after the 6402??
maybe you got some part numbers from manufacturers?

#### arcom

##### New Member
Hi there.

bogdanfirst, perhaps you can use HCF4034 (MC14034) to do the same
thing as 6402 UART. It's a parellel-to-serial & serial-to-parallel converter.
Haven't tested this, though...

#### mechie

##### New Member
6402 UART RIP

There I go again... talking out of date!
The good old 6402 has gone obsolite, I can't find a supplier with stocks of this superb component so if you see one for sale and you think it may be useful in the future ...

GRAB IT !

I am now looking for some sort of replacement for an up-n-coming project so I will play with a 4034 (thanx arcom for the suggestion) and see how well it fits in.

bogdanfirst, we seem to be on similar (par-ser-par) problems ... pm me if you find any new components, I'll do the same.

#### arcom

##### New Member
no problemos, glad I can help 8)

#### bogdanfirst

##### New Member
here is what i found , but no part name listed:
and
and ill keep looking

#### mechie

##### New Member
6402 UART

Bogdanfirst I have given up with the MC14034 as it requires too much support logic.
The FUART from www.chipcenter.com is a bit of code that can be written to a PLA or similar - not a component - doesn't seem a viable option.

As I see it there are now two options (soon there will only be one ...)
[1] program a microcontroller (could be done and could achieve additional coding/decoding/control) but if you aren't geared up to write and program it could be daunting.
[2] I have found a supplier with a limited stock of 6402 UARTs (UK price around £9). This could be the easiest option as there is no debugging of code and will require little more than an RC oscillator (remember a full circuit is required at both ends of the line.
**broken link removed** (8 lines from the bottom of the page).

#### bogdanfirst

##### New Member
yep....
anyway i have given up this idea......
think that i am going to use a DTMF...much better

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