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Another question involving a monostable.

Started by Pimpom January 31, 2013
Scheme: I have these three different sources of irregular 
low-repetition-rate pulses, no two occurring at the same 
time, and I want to send them over a long 2-core shielded 
cable. I suppose they could be sent as serial data, but my 
knowledge of MCUs is limited and dedicated encoder-decoder 
pair ICs introduce uncertainty periods of tens of 
milliseconds. Such periods can be tolerated but undesireable 
if they can be avoided.

I thought I'd found a clever solution by encoding the 
signals to 01, 10 and 11 signals and decoding them at the 
receiving end with a 2-to-4 line decoder like the CD4555. 
Then it occurred to me that slight differences in wire 
length and cable and stray capacitances could introduce 
different time delays between the two lines and cause 
decoding errors. The 11 signal in particular could be 
mistaken for a momentary 01 or 10 pulse. Subsequent 
controlled stages will not be adversely affected by an 
erronous sub-millisecond 01 or 10 pulse at the rising edge 
of the 11 signal, but the falling edge could cause problems.

Proposed solution: Have the decoded 11 pulse at the receiver 
trigger a monostable. The 11 pulse is a reset signal and 
will override the effect of any spurious 01 or 10 signal 
during the mono period..

Have I missed anything? 


On 2013-01-31, Pimpom <Pimpom@invalid.invalid> wrote:

> Proposed solution: Have the decoded 11 pulse at the receiver > trigger a monostable. The 11 pulse is a reset signal and > will override the effect of any spurious 01 or 10 signal > during the mono period.. > > Have I missed anything?
how about voltage levels. signal the third state by a half-voltage on both wires, that way timing irregularities give a phantom signal. -- &#9858;&#9859; 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
On Thu, 31 Jan 2013 09:31:30 +0530, "Pimpom" <Pimpom@invalid.invalid>
wrote:

>Scheme: I have these three different sources of irregular >low-repetition-rate pulses, no two occurring at the same >time, and I want to send them over a long 2-core shielded >cable. I suppose they could be sent as serial data, but my >knowledge of MCUs is limited and dedicated encoder-decoder >pair ICs introduce uncertainty periods of tens of >milliseconds. Such periods can be tolerated but undesireable >if they can be avoided. > >I thought I'd found a clever solution by encoding the >signals to 01, 10 and 11 signals and decoding them at the >receiving end with a 2-to-4 line decoder like the CD4555. >Then it occurred to me that slight differences in wire >length and cable and stray capacitances could introduce >different time delays between the two lines and cause >decoding errors. The 11 signal in particular could be >mistaken for a momentary 01 or 10 pulse. Subsequent >controlled stages will not be adversely affected by an >erronous sub-millisecond 01 or 10 pulse at the rising edge >of the 11 signal, but the falling edge could cause problems. > >Proposed solution: Have the decoded 11 pulse at the receiver >trigger a monostable. The 11 pulse is a reset signal and >will override the effect of any spurious 01 or 10 signal >during the mono period.. > >Have I missed anything? >
Since all "desired" signals contain a "1", use that transition to trigger a monostable that samples both lines at time-out. But that will force/require a minimum signal time length. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Thu, 31 Jan 2013 08:48:20 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Thu, 31 Jan 2013 09:31:30 +0530, "Pimpom" <Pimpom@invalid.invalid> >wrote: > >>Scheme: I have these three different sources of irregular >>low-repetition-rate pulses, no two occurring at the same >>time, and I want to send them over a long 2-core shielded >>cable. I suppose they could be sent as serial data, but my >>knowledge of MCUs is limited and dedicated encoder-decoder >>pair ICs introduce uncertainty periods of tens of >>milliseconds. Such periods can be tolerated but undesireable >>if they can be avoided. >> >>I thought I'd found a clever solution by encoding the >>signals to 01, 10 and 11 signals and decoding them at the >>receiving end with a 2-to-4 line decoder like the CD4555. >>Then it occurred to me that slight differences in wire >>length and cable and stray capacitances could introduce >>different time delays between the two lines and cause >>decoding errors. The 11 signal in particular could be >>mistaken for a momentary 01 or 10 pulse. Subsequent >>controlled stages will not be adversely affected by an >>erronous sub-millisecond 01 or 10 pulse at the rising edge >>of the 11 signal, but the falling edge could cause problems. >> >>Proposed solution: Have the decoded 11 pulse at the receiver >>trigger a monostable. The 11 pulse is a reset signal and >>will override the effect of any spurious 01 or 10 signal >>during the mono period.. >> >>Have I missed anything? >> > >Since all "desired" signals contain a "1", use that transition to >trigger a monostable that samples both lines at time-out. > >But that will force/require a minimum signal time length. > > ...Jim Thompson
As in... http://www.analog-innovations.com/SED/Pimpom_Decoder.pdf Reset is via the 0-0 state. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Maybe send the signal with a gray code, that is, just avoid the 01 to 10 
transition.


Offhand:

- AC modulate (using a variety of encodings).  A simple example would be 
keyed tones, one oscillator and one decoder for each signal.

- Make a simple DAC: combine the pulses, with binary weighted resistors, 
into a summing amp.  Receive with comparators.  As miso said, Gray code 
helps here.

- Do it in serial, but make it a real hack job, way fewer transistors than 
a uC.  Example: send a long pulse to reset the receiver (use a timer to 
measure the pulse width).  Then send a series of pulses, which are gated 
into a counter.  Counter increments to whatever bit pattern is required 
(you might use a "one-hot" shift register since your signals are 
one-at-a-time).  When counting is done, another long pulse (of opposite 
polarity or different time length) can be used to clock a second register, 
buffering the data, or to enable the outputs for the pulse.

Regular (asynchronous) serial can be used, too, but you need more accurate 
timing.  Over a couple of bits, it's probably not a problem to use an RC 
oscillator for the job.  In which case, you could use the start bit as an 
enable to start the timer, which keeps ticking for a certain number of 
cycles (an analog counter can be made with a couple of transistors, by the 
way, so you don't have to wire up a counter and gates to do it).

Note these will work with a single conductor (and ground) transmission 
line, and can be suitable for any combination of signal lines, not just 
one-at-a-time (you can usually squeeze them together with an N-to-2^N 
decoder, as you noted).

Tim

-- 
Deep Friar: a very philosophical monk.
Website: http://seventransistorlabs.com

"Pimpom" <Pimpom@invalid.invalid> wrote in message 
news:ked3up$p09$1@news.albasani.net...
> Scheme: I have these three different sources of irregular > low-repetition-rate pulses, no two occurring at the same time, and I > want to send them over a long 2-core shielded cable. I suppose they > could be sent as serial data, but my knowledge of MCUs is limited and > dedicated encoder-decoder pair ICs introduce uncertainty periods of tens > of milliseconds. Such periods can be tolerated but undesireable if they > can be avoided. > > I thought I'd found a clever solution by encoding the signals to 01, 10 > and 11 signals and decoding them at the receiving end with a 2-to-4 line > decoder like the CD4555. Then it occurred to me that slight differences > in wire length and cable and stray capacitances could introduce > different time delays between the two lines and cause decoding errors. > The 11 signal in particular could be mistaken for a momentary 01 or 10 > pulse. Subsequent controlled stages will not be adversely affected by an > erronous sub-millisecond 01 or 10 pulse at the rising edge of the 11 > signal, but the falling edge could cause problems. > > Proposed solution: Have the decoded 11 pulse at the receiver trigger a > monostable. The 11 pulse is a reset signal and will override the effect > of any spurious 01 or 10 signal during the mono period.. > > Have I missed anything? >
On Thu, 31 Jan 2013 13:21:41 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Thu, 31 Jan 2013 08:48:20 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Thu, 31 Jan 2013 09:31:30 +0530, "Pimpom" <Pimpom@invalid.invalid> >>wrote: >> >>>Scheme: I have these three different sources of irregular >>>low-repetition-rate pulses, no two occurring at the same >>>time, and I want to send them over a long 2-core shielded >>>cable. I suppose they could be sent as serial data, but my >>>knowledge of MCUs is limited and dedicated encoder-decoder >>>pair ICs introduce uncertainty periods of tens of >>>milliseconds. Such periods can be tolerated but undesireable >>>if they can be avoided. >>> >>>I thought I'd found a clever solution by encoding the >>>signals to 01, 10 and 11 signals and decoding them at the >>>receiving end with a 2-to-4 line decoder like the CD4555. >>>Then it occurred to me that slight differences in wire >>>length and cable and stray capacitances could introduce >>>different time delays between the two lines and cause >>>decoding errors. The 11 signal in particular could be >>>mistaken for a momentary 01 or 10 pulse. Subsequent >>>controlled stages will not be adversely affected by an >>>erronous sub-millisecond 01 or 10 pulse at the rising edge >>>of the 11 signal, but the falling edge could cause problems. >>> >>>Proposed solution: Have the decoded 11 pulse at the receiver >>>trigger a monostable. The 11 pulse is a reset signal and >>>will override the effect of any spurious 01 or 10 signal >>>during the mono period.. >>> >>>Have I missed anything? >>> >> >>Since all "desired" signals contain a "1", use that transition to >>trigger a monostable that samples both lines at time-out. >> >>But that will force/require a minimum signal time length. >> >> ...Jim Thompson > >As in... > > http://www.analog-innovations.com/SED/Pimpom_Decoder.pdf > >Reset is via the 0-0 state. > > ...Jim Thompson
Now with a demonstration of one wire signal delayed relative to the other. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> schreef 
in bericht news:3hklg85c3qkki2hqosishgdranf5v1krbn@4ax.com...
> On Thu, 31 Jan 2013 08:48:20 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Thu, 31 Jan 2013 09:31:30 +0530, "Pimpom" <Pimpom@invalid.invalid> >>wrote: >> >>>Scheme: I have these three different sources of irregular >>>low-repetition-rate pulses, no two occurring at the same >>>time, and I want to send them over a long 2-core shielded >>>cable. I suppose they could be sent as serial data, but my >>>knowledge of MCUs is limited and dedicated encoder-decoder >>>pair ICs introduce uncertainty periods of tens of >>>milliseconds. Such periods can be tolerated but undesireable >>>if they can be avoided. >>> >>>I thought I'd found a clever solution by encoding the >>>signals to 01, 10 and 11 signals and decoding them at the >>>receiving end with a 2-to-4 line decoder like the CD4555. >>>Then it occurred to me that slight differences in wire >>>length and cable and stray capacitances could introduce >>>different time delays between the two lines and cause >>>decoding errors. The 11 signal in particular could be >>>mistaken for a momentary 01 or 10 pulse. Subsequent >>>controlled stages will not be adversely affected by an >>>erronous sub-millisecond 01 or 10 pulse at the rising edge >>>of the 11 signal, but the falling edge could cause problems. >>> >>>Proposed solution: Have the decoded 11 pulse at the receiver >>>trigger a monostable. The 11 pulse is a reset signal and >>>will override the effect of any spurious 01 or 10 signal >>>during the mono period.. >>> >>>Have I missed anything? >>> >> >>Since all "desired" signals contain a "1", use that transition to >>trigger a monostable that samples both lines at time-out. >> >>But that will force/require a minimum signal time length. >> >> ...Jim Thompson > > As in... > > http://www.analog-innovations.com/SED/Pimpom_Decoder.pdf > > Reset is via the 0-0 state. > > ...Jim Thompson > -- > | James E.Thompson, CTO | mens | > | Analog Innovations, Inc. | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | Phoenix, Arizona 85048 Skype: Contacts Only | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > I love to cook with wine. Sometimes I even put it in the food.
Suppose your encoding will fail Jim. A 08 AND gates output only goes high when both inputs are high. But this will never happen as according to the OPs question the pulses are separated in time. petrus bitbyter
"petrus bitbyter" <petrus.bitbyter@hotmail.com> wrote in 
message 
news:510b182a$0$6329$e4fe514c@dreader35.news.xs4all.nl...
> > "Jim Thompson" > <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> > schreef in bericht > news:3hklg85c3qkki2hqosishgdranf5v1krbn@4ax.com... >> On Thu, 31 Jan 2013 08:48:20 -0700, Jim Thompson >> <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> >> wrote: >> >>>On Thu, 31 Jan 2013 09:31:30 +0530, "Pimpom" >>><Pimpom@invalid.invalid> >>>wrote: >>> >>>>Scheme: I have these three different sources of >>>>irregular >>>>low-repetition-rate pulses, no two occurring at the same >>>>time, and I want to send them over a long 2-core >>>>shielded >>>>cable. I suppose they could be sent as serial data, but >>>>my >>>>knowledge of MCUs is limited and dedicated >>>>encoder-decoder >>>>pair ICs introduce uncertainty periods of tens of >>>>milliseconds. Such periods can be tolerated but >>>>undesireable >>>>if they can be avoided. >>>> >>>>I thought I'd found a clever solution by encoding the >>>>signals to 01, 10 and 11 signals and decoding them at >>>>the >>>>receiving end with a 2-to-4 line decoder like the >>>>CD4555. >>>>Then it occurred to me that slight differences in wire >>>>length and cable and stray capacitances could introduce >>>>different time delays between the two lines and cause >>>>decoding errors. The 11 signal in particular could be >>>>mistaken for a momentary 01 or 10 pulse. Subsequent >>>>controlled stages will not be adversely affected by an >>>>erronous sub-millisecond 01 or 10 pulse at the rising >>>>edge >>>>of the 11 signal, but the falling edge could cause >>>>problems. >>>> >>>>Proposed solution: Have the decoded 11 pulse at the >>>>receiver >>>>trigger a monostable. The 11 pulse is a reset signal and >>>>will override the effect of any spurious 01 or 10 signal >>>>during the mono period.. >>>> >>>>Have I missed anything? >>>> >>> >>>Since all "desired" signals contain a "1", use that >>>transition to >>>trigger a monostable that samples both lines at time-out. >>> >>>But that will force/require a minimum signal time length. >>> >>> ...Jim Thompson >> >> As in... >> >> >> http://www.analog-innovations.com/SED/Pimpom_Decoder.pdf >> >> Reset is via the 0-0 state. >> > > Suppose your encoding will fail Jim. A 08 AND gates output > only goes high when both inputs are high. But this will > never happen as according to the OPs question the pulses > are separated in time. > > petrus bitbyter
That's right.
"Pimpom" <Pimpom@invalid.invalid> wrote in message 
news:ked3up$p09$1@news.albasani.net...
> Scheme: I have these three different sources of irregular > low-repetition-rate pulses, no two occurring at the same > time, and I want to send them over a long 2-core shielded > cable. I suppose they could be sent as serial data, but my > knowledge of MCUs is limited and dedicated encoder-decoder > pair ICs introduce uncertainty periods of tens of > milliseconds. Such periods can be tolerated but > undesireable if they can be avoided. > > I thought I'd found a clever solution by encoding the > signals to 01, 10 and 11 signals and decoding them at the > receiving end with a 2-to-4 line decoder like the CD4555. > Then it occurred to me that slight differences in wire > length and cable and stray capacitances could introduce > different time delays between the two lines and cause > decoding errors. The 11 signal in particular could be > mistaken for a momentary 01 or 10 pulse. Subsequent > controlled stages will not be adversely affected by an > erronous sub-millisecond 01 or 10 pulse at the rising edge > of the 11 signal, but the falling edge could cause > problems. > > Proposed solution: Have the decoded 11 pulse at the > receiver trigger a monostable. The 11 pulse is a reset > signal and will override the effect of any spurious 01 or > 10 signal during the mono period.. > > Have I missed anything? >
Thanks for your interest, everyone and sorry about the late reply. Different time zones and some social obligations. Jim, I'm afraid petrus is right. The AND gates will never change state with my signals. Jasen, Tim & miso, each of your ideas has its own merit. But my application can tolerate certain glitches as explained earlier and I want to keep things as simple as possible. Here's a simplified diagram of the scheme I had in mind. Do you see anything wrong with it? http://img248.imageshack.us/img248/1835/323encodedecode.png