Re: Understanding X10 Dims???

[nobody@xxxxxxxxxxxx (Dave Houston)]

I'm not sure I understand your question.

I have noticed anomolies in what the CM11A reports but I haven't determined
that there is any pattern (which doesn't mean there is none).

When sending, the CM11A only uses 5 bits for the Dim/Bright value which,
according to X-10 documentation, can only be 0-22. Other PLC interfaces send
N+1 contiguous DIM/BRT as I explained in the post that was quoted. I don't
think the variations you see are meaningful because none of the transmitters
have that kind of resolution but I've never tried measuring the voltage from
a lamp module. AFAIK the only way to get finer resolution at the receiver is
with a series of microsteps and that takes a great deal of time.

I have a CM15A and have made a ribbon cable extension so I could move the
MCU to a breadboard and expose all of the signal lines. I've used it with my
scope card to record the powerline signals when sending dim levels 0-22 with
a CM11A. I cannot convert them to GIFs and publish them because of the need
to scroll the scope display - 22 contiguous dims needs 22*11=242 half
cycles. It's easy to count the number of contiguous dims by just counting
the start codes. The number of contiguous dims is equal to the same 0-22
sent by the CM11A. Another CM11A that was reporting the same bitstream has
to be fudging the extra bits of resolution it reports as they are not on the
powerline.

Neil Cherry has modified a TW523 to report the powerline bitstream. Maybe he
could record some sequences for you.

If I remember, I'll try to connect a meter to the output side of a lamp
module and see whether I can plot voltage vs. microsteps as well as voltage
vs. 1-22 brights.

Charles Sullivan <cwsulliv@xxxxxxxxxxxx> wrote:

>Robert,
>Thanks for your response.  Yes, Dave's post is clear, but it
>doesn't answer my questions.
>
>I can direct the CM11A to send the same dims multiple times
>(with a few seconds delay in between) but the dims reported by
>another CM11A (looking at the actual byte reported, not converting
>to a percentage) vary by 1/210, occasionally 2/210. Why the
>variation?  And what exactly is being sent over the PL which
>accounts for the "retro" effect of the higher (by 1 or 2) dim
>value, which is most noticeable with the LM14A but also observable
>with a standard X10 lamp module.
>
>I was hoping that someone who had monitored the power line with
>something other than a CM11A, or who had knowledge of the
>hardware/firmware with regard to dims, could provide some insight
>into what's happening.
>
>Regards,
>Charles Sullivan
>
>On Mon, 08 Aug 2005 14:49:03 -0400, Robert Green wrote:
>
>> I am going to take the liberty of repeating a Dave Houston post from a while
>> back to hopefully free a little more time for him to design the "killer"
>> powerline analyzer.  :-)
>>
>> ----------------------------------------------------------------------------
>> ----
>>
>> Re: CM11A Protocol Question -- Posted by Dave Houston on 09-06-04 06:03
>>
>> It's been several years since I worked on this so the details are a bit hazy
>> and it's early AM (I'm only on my first dose of caffiene) so you might want
>> to look at my VB source code (cm11a.zip) for the CM11A at...
>>
>> http://www.mbx-usa.com/files.htm
>>
>> You cannot dim TO a specific value (unless you track the level of each
>> address). You can only dim BY a specific increment.
>>
>> Standard dim & bright use approximately 6% steps (i.e. 16 steps between min
>> & max). The CM11A documentation says there are 210 discrete levels. (It's
>> hard to discern more than about 150.) As best I recall, I used a little
>> trial and error to decide on the increments to use with the CM11A as the
>> CM11A converts them to standard steps. If you send an increment less than
>> 3-4% to the CM11A, you'll get a microstep (also demonstrated in the VB
>> source) of about 0.6% (i.e. 1/210).
>>
>> You really need to study the PLC documentation to understand what's actually
>> sent to the powerline for Dim/Bright - noting the fact that there's no gap
>> between multiple commands. Phil Kingery's articles (see the Home Toys
>> archives) also help but I never fully understood them (if I FULLY understand
>> them now) until Dan Lanciani explained them using the following simple
>> notation.
>>
>> DIM = 1 PLC dim command (Bright works the same)
>>
>> Sending a single DIM results in a microstep. Sending n contiguous DIMs
>> results in n-1 standard 6% steps. Below, I use _ to represent no GAP between
>> PLC commands.
>>
>> DIM_DIM = 6%
>> DIM_DIM_DIM = 12%
>> DIM_DIM_DIM_DIM = 18%
>> ...
>> 17 gapless DIMs = 100%
>>
>> But, using a space to indicate more than 3 idle cycles...
>>
>> DIM DIM = two microdims
>>
>> This is further complicated by the fact that a GAP is defined as 3 or more
>> idle cycles (6 or more idle half cycles) so a smaller gap between DIMs is
>> still seen as a contiguous stream.
>>
>> Another complication (for grasping the details) is that the CM11A only
>> reports the cumulative result for Dim/Bright - it doesn't report the number
>> of PLC commands. Those with the latest firmware wait for the end of the
>> stream (or until it's seen 100% worth) to report. You really need something
>> that gives you each bit at the PLC level to understand.
>>
>> Clear? ;)
>>
>>
>> "Charles Sullivan" <cwsulliv@xxxxxxxxxxxx> wrote in message
>> news:pan.2005.08.08.15.46.56.590079@xxxxxxxxxxxxxxx
>>> Using a CM11A to monitor dims (brights) on the power line, I notice
>>> that most X10 transmitters, e.g., CM11A, Mini/Maxi-controllers,
>>> RR501, send dims (brights) according to the formula:
>>>   dims = 11*N + X
>>> where N >= 0 and X varies randomly - usually 2 or 3, sometimes 4.
>>> The CM11A reports a maximum of 210 dims.
>>>
>>> The variation in X does not appear to be an imprecision in the
>>> monitoring interface circuitry - two CM11As on line simultaneously
>>> always report identical received values.
>>>
>>> A strange thing about X is that a value of 3 or 4 produces _less_
>>> actual dimming than 2.  The effect is difficult to see with a
>>> standard X10 lamp module (and digital RMS multimeter) because of
>>> short term fluctuations in line voltage, but is very dramatic
>>> with X10's LM14A 2-way lamp module.  With the LM14A, a plot of
>>> either extended level (0-63) or output voltage versus received
>>> dims (2-210 dims from the fully ON state) looks like a sawtooth
>>> curve with "tooth height" of as many as 6 extended levels or
>>> almost 10 percent.  (There's a similar sawtooth curve from the
>>> fully OFF state when brights are received.)
>>>
>>> Can any of the X10 hardware/firmware gurus on this newsgroup
>>> explain the reason for the variability of X in the transmitted
>>> dims and the strange retro effect of X = 3,4 versus X = 2 on X10
>>> modules?  Thanks for your help.
>>>
>>> Regards,
>>> Charles Sullivan
>>>
>>>
>>>
>>>
>>>
>>>
>>>