[sdiy] Four bit to serial translator

[Peter Grenader]

wait wait wait...Rene, you always talk too fast for me.  Are you saying the
same bit connected to each input of the XORs, except one has an R/C?

sort of like the old freq2uncy doubler trick....hmmm.  Spike determined by
the R/C....hmmm.  this sound nice and easy.

Harry - I tried the magnitude comparator, but with a 74HC85 in conjunction
with a 4042 latch.  I thought this was my ticket at first, but I was having
misreads all over the place.





René Schmitz wrote:

> Hi Peter and Harry,
> 
> Even simpler same principal concept, but without the register:
> 
> Use an X(N)OR gate for each bit, and put an RC combination at one of the
> inputs, and feed the bit directly to the other. Result is a short spike
> when that bit changes. replicate n times. OR all XORs together.
> 
> Cheers,
> René
> 
> harrybissell wrote:
>> Magnitude Comparator ??? CD4585B
>> 
>> Make an n-1 copy of your word (it could be generated by a high speed
>> clock or the falling edge of your existing clock, whatever...
>> 
>> compare the new word with the n-1 word for equality. If it is equal
>> there is no change, if not equal, it changed.
>> 
>> This is basically an array of x-or gates, you could do it that way too...
>> 
>> H^) harry
>> 
>> 
>> Peter Grenader wrote:
>> 
>> 
>>> Guys and gal,
>>> 
>>> I'm in a bit of a pickle and it's getting sour here - thought you cold throw
>>> me a life raft.
>>> 
>>> I've added an asynchronous VC to Milton.  Quite the bomb.  It doesn't give
>>> two sheets what the incoming pulse is doing, or even if there IS an incoming
>>> pulse for that matter - when the VC input's A to D changes state, the
>>> counter immediately reacts.  With this you can now set the start and end
>>> step to wherever you want, plus achieve some amazing non-linear
>>> progressions. Driving it with a sine wave being particularly interesting as
>>> the sequence accelerates at both ends.
>>> 
>>> Problem is, as the name implies -  it's asynchronous. It functionally
>>> remains a bit of a lame duck as there no way of syncing anything to it.  So,
>>> unless you're planning on a legato glissandi, you're screwed.
>>> 
>>> I've worked out a way to extract a timing pulse, but its involving more
>>> parts than I like, and I'm certain there's an easier way.
>>> 
>>> What I need is a short pulse each time the 4 bit word changes.  I tried just
>>> monitoring the LSB, that works until it jumps to another of the same parity
>>> and then it's lost.  I tired doubling the speed of the LSB to synthesize it
>>> and that was totally the wrong direction.  I've thought through parity
>>> comparators, but again, that leaves holes.
>>> 
>>> So what I've ended up doing is taking the outputs of the 4050 (all sixteen
>>> of them) and shaping those into pulses rather than gates and summing them
>>> into one continuos stream, each with a 50ms on time.
>>> 
>>> Although it took only one sentence to describe it, that function requires
>>> sixteen transistors, 52 resistors, 22caps and 5 ICs.  In short - forget it.
>>> 
>>> Any competent PIC programmers out there who are up for a challenge?
>>> 
>>> If nay - anyone have a CMOS logic level solution???
>>> 
>>> thanks in advance,
>>> 
>>> Peter
>> 
>> 
>> 
>