Help with cleaning up noisy 10 bps communication

On Tue, 12 Aug 2014 10:11:27 -0700, makolber wrote:

> On Tuesday, August 12, 2014 12:48:56 PM UTC-4, BasicPoke wrote:
>> Those are some great ideas, thanks guys.  I should have known about the
>> 
>> termination with characteristic impedance, but did not occur to me.  I
>> will
>> 
>> have to check this out, as I'm not the hardware guy on this.  I need to
>> 
>> figure out how much detail I can go into without getting into trouble.
>> 
>> 
>> 
>> We have control of the hardware on both ends of the cable, but
>> generally
>> 
>> not control over the cable and motor.  Not sure how the characteristics
>> 
>> change with the motor on, but I know there is lots of noise at various
>> 
>> frequencies.
>> 
>> Ron
>> 
>> 
>> 
> 
> So this brings up a question I have tried to raise here beofre.
> And nothing personal to Ron, this is a generic issue.
> 
> It seems clear Ron's task is in  a professional setting, i.e.  his
> empoyer is paying him to figure this out.  I'd like to hear a discussion
> about "giving away" this kind of information given the job market we are
> in.  If Ron were not able to come here and get this kind of help for
> free, Ron's employer might have to hire one of us.
> 
> This issue was brought up often the the alt.hvac group where the
> professional hvac guys would,  shall we say,  respond in a very impolite
> fashion, to "homeowners" looking for free help.  And after thinking
> about it, I think they may have a point.
> 
> I'd like to hear other opinions about giving away knowledge of one's
> craft.
> I like information to be free, but I also like to be paid for my
> expertiese.  How do we balance these?
> 
> Again, sorry Ron, I used your particular question as an example, nothing
> personal.

When you see me responding on this newsgroup, I'm in the role of the nice 
old lady at the supermarket who's handing out littly itty bitty yummy 
things on toothpicks, right next to the freezer case where you can buy 
whole boxes of the stuff.  You may notice that those nice little old 
ladies never say "GO BUY IT, BUSTER!"  That's because they're hired 
because they know that being nice sells.  And if one person comes around 
too much, they can always nicely say "oh, I'm sorry honey, we can't give 
away too much to any one person".

So here -- have another tiny tidbit of information on a toothpick.

My answers pop up in web searches, or the original poster decides he needs 
my help, and I get business.  This must be working, because nearly all of 
my business comes to me via email from people I don't know, rather than 
from a web of contacts.

It's quite easy to politely limit the amount of information going out 
while hinting that more could be had for a price, and I do just that: "the 
answer to your question is so involved that I would have to expend a 
significant amount of time on it, and I'll only do that if I'm under 
contract".  There's no need to be rude, or to accuse the OP of trying to 
gouge for information, or anything.

Frankly, being a rudesby, like the guys on alt.hvac, is just an indirect 
way of saying "please don't hire me, ever, for anything."

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Tue, 12 Aug 2014 17:36:44 +0000, Eric Jacobsen wrote:

> On Tue, 12 Aug 2014 10:11:27 -0700 (PDT), makolber@yahoo.com wrote:
> 
>>I'd like to hear other opinions about giving away knowledge of one's
>>craft.=
>>=20 I like information to be free, but I also like to be paid for my
>>expertiese=
>>.  How do we balance these?
>>
>>Again, sorry Ron, I used your particular question as an example, nothing
>>pe=
>>rsonal.
>>
>>Mark

<< snip >>

> I think it still boils down to a personal choice, though.   For the most
> part, I think the sort of people who hang out on comp.dsp are already
> the sort of people that are willing to help at least a certain amount,
> or it wouldn't exist as it does.

I use USENET as a pressure valve.  At the moment I'm trying to figure out 
a graceful way to test a rather complicated algorithm that involves 
several boards talking to each other via serial ports.  My self-imposed 
constraint is that it all has to happen successfully on a PC before it 
gets burned onto flash on an embedded processor, and at the moment I'm 
struggling with how to gracefully take my embedded timer class, which is 
perfectly suited to its environment, and make it work on a PC, for which 
environment it isn't well suited at all.

Rather than screaming or beating the walls, or going and building model 
airplanes for hours, I take a break and answer questions here.  When I was 
in the corporate world, I was one of those guys who'd get up and interrupt 
other people's work at times like this (and, usually, accept it when the 
guys I tended to bug came and bugged me).

(in point of fact, as I was writing that first paragraph I think I figured 
out how to break the ice on my test development and move forward -- so 
USENET does have its uses beyond just puffing myself off to a world of 
potential customers).

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Tim Wescott <seemywebsite@myfooter.really> wrote:

> On Tue, 12 Aug 2014 10:11:27 -0700, makolber wrote:
(snip)
>> So this brings up a question I have tried to raise here beofre.
>> And nothing personal to Ron, this is a generic issue.
 
>> It seems clear Ron's task is in  a professional setting, i.e.  his
>> empoyer is paying him to figure this out.  I'd like to hear a discussion
>> about "giving away" this kind of information given the job market we are
>> in.  If Ron were not able to come here and get this kind of help for
>> free, Ron's employer might have to hire one of us.
 
(snip)

> When you see me responding on this newsgroup, I'm in the role of the nice 
> old lady at the supermarket who's handing out littly itty bitty yummy 
> things on toothpicks, right next to the freezer case where you can buy 
> whole boxes of the stuff.  You may notice that those nice little old 
> ladies never say "GO BUY IT, BUSTER!"  That's because they're hired 
> because they know that being nice sells.  And if one person comes around 
> too much, they can always nicely say "oh, I'm sorry honey, we can't give 
> away too much to any one person".

I don't watch it all that often, but there is "What would you do?".

One time they had someone (who worked for the show, in case you
don't know how it works) go in to the store and take the whole
plate if samples and toothpicks. (No lady around.) 
Even took that plate!  Then watch what other customers say.

As I remember it, one figured that she (I think it was a she)
had a starving family at home, and needed the food.

Reminds me of wondering about Coursera, giving away for free
courses that others are paying for. Are there schools complaining
about the loss of business, as students take the Coursera course
instead of attending school?  (Not to mention writing books 
where people could learn instead of attending class.)

How about if someone posts an idea so useful that someone else
goes out and patents it? 

-- glen

On 12/08/14 21:28, glen herrmannsfeldt wrote:
> How about if someone posts an idea so useful that someone else
> goes out and patents it?

Lawyers get a lot of money before the patent is ruled invalid
because the idea wasn't novel since it had been published.

On Tue, 12 Aug 2014 23:12:48 +0100, Tom Gardner
<spamjunk@blueyonder.co.uk> wrote:

>On 12/08/14 21:28, glen herrmannsfeldt wrote:
>> How about if someone posts an idea so useful that someone else
>> goes out and patents it?
>
>Lawyers get a lot of money before the patent is ruled invalid
>because the idea wasn't novel since it had been published.
>

Yeah, it'd be pretty easy to show prior art by pointing to the post in
comp.dsp with a date and time stamp.  ;)



Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com

Hi,

"characteristic impedance" is a dead end at 10 Hz.
It matters when the cable is not short anymore compared to the wavelength.
Which, at 10 Hz, is several thousands of kilometers.

A proper termination of the signal source is another matter. If, say, the
source is designed to drive a 100 ohms resistance, the receiver should
implement that, regardless of the wire in-between.

One possible filter (and this might be the "windowed sinc" proposed
earlier) is moving average filtering over the symbol length.
The detector continuously averages the signal over the length of one pulse
(100 ms): For example, if the ADC runs at 100 kHz, store 10000 samples in a
FIFO and continuously average them. 
This can be done efficiently by adding the FIFO input samples into an
integrator, and subtracting the FIFO output samples (this is also known as
"CIC" filter),

It's a matched filter to the known rectangular pulse shape, and therefore,
under some standard assumptions (no ISI, white noise) optimal. As you
described, the situation may be more complex, but I'd use this as a
starting point.
	 

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mnentwig <24789@dsprelated> wrote:
 
> "characteristic impedance" is a dead end at 10 Hz.
> It matters when the cable is not short anymore compared to the 
> wavelength. Which, at 10 Hz, is several thousands of kilometers.

Yes, but you have to be a little careful. If, for example, you have
a 10 baud system, but the signal transitions in 100ns, then there
are frequencies up to 10MHz or more that matter. 

Series termination (a resistor between the source and the transmission
line) is sometimes used. It is, for example, commonly used on the
data bus driving SDRAM on modern systems. It reduces the high
frequency components generated and, even more reduces the reflections
if there is a reflection from the other end.
 
> A proper termination of the signal source is another matter. If, say, the
> source is designed to drive a 100 ohms resistance, the receiver should
> implement that, regardless of the wire in-between.
 
> One possible filter (and this might be the "windowed sinc" proposed
> earlier) is moving average filtering over the symbol length.
> The detector continuously averages the signal over the length of 
> one pulse (100 ms): For example, if the ADC runs at 100 kHz, 
> store 10000 samples in a FIFO and continuously average them. 
> This can be done efficiently by adding the FIFO input samples 
> into an integrator, and subtracting the FIFO output samples 
> (this is also known as "CIC" filter),

(snip)

-- glen

>> then there are frequencies up to 10MHz or more that matter. 
Erm, no. That would be a million times the baud rate.

As a rule of thumb, fit two bits into one cycle (look at the fundamental
component of a 010101... sequence). Analog Telefax is the classical
textbook example. Some excess bandwidth is OK, a factor of 10 maybe.

Bandwidth must be limited, otherwise the cable becomes the antenna of a
long range thunderstorm detector.
	 

_____________________________		
Posted through www.DSPRelated.com

>So this brings up a question I have tried to raise here beofre.
>And nothing personal to Ron, this is a generic issue.
>
>It seems clear Ron's task is in  a professional setting, i.e.  his empoyer
=
>is paying him to figure this out.  I'd like to hear a discussion about
"giv=
>ing away" this kind of information given the job market we are in.  If Ron
=
>were not able to come here and get this kind of help for free, Ron's
employ=
>er might have to hire one of us.=20
>
>This issue was brought up often the the alt.hvac group where the
profession=
>al hvac guys would,  shall we say,  respond in a very impolite fashion, to
=
>"homeowners" looking for free help.  And after thinking about it, I think
t=
>hey may have a point.=20
>
>I'd like to hear other opinions about giving away knowledge of one's
craft.=
>=20
>I like information to be free, but I also like to be paid for my
expertiese=
>.  How do we balance these?
>
>Again, sorry Ron, I used your particular question as an example, nothing
pe=
>rsonal.
>
>Mark
>
>
Mark, you hijacked my thread.  When you want to change the topic of a
thread on an online forum, it is polite to start a new thread (this will be
your thread).
Ron	 

_____________________________		
Posted through www.DSPRelated.com

>>> then there are frequencies up to 10MHz or more that matter. 
>Erm, no. That would be a million times the baud rate.
>
>As a rule of thumb, fit two bits into one cycle (look at the fundamental
>component of a 010101... sequence). Analog Telefax is the classical
>textbook example. Some excess bandwidth is OK, a factor of 10 maybe.
>
>Bandwidth must be limited, otherwise the cable becomes the antenna of a
>long range thunderstorm detector.
>	 
That is something we were just talking about, limiting the rise and fall
time of the signal (at the driver), which is not being done now.  This
would reduce the ringing I believe.  But we are very reluctant to add
active components because of reliability issues.  We are working at high
temps.

The cable is underground, vertical, to a well motor, so I don't believe it
can act as an antenna.
Ron	 

_____________________________		
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