On Mon, Dec 13, 2010 at 3:30 PM, Atkinson, Lee <
Lee.Atkinson@xxxxxx> wrote:
> Edgar, in fact the only guy I know using a digital communication method for
> ID is Dell. To Gary V's question, have we rationalized the messages that we
> want to send to the sink, with expected latency ? Have we also confirmed
> what kinds of devices would use active messaging?
>
> My thinking on a few topics;
> a. There is no A/D or microprocessor needed for a simple proportional
> signal. Though A/D and processors are common in notebooks, simpler devices
> could use as little as a transistor and resistor (if they need to discern
> the power capability of the AC adapter at all).
>
> b. The only negotiation for power is simply to declare a connected load; we
> are on the path of a single terminal voltage and not a sink programmable
> voltage (as was contemplated at first and would have required the more
> complex signaling).
> Spark Free does not need the ID pin, certainly our Cupertino friends vary
> to terminal voltage as a function of VCC load (the spark in this case is
> particularly interesting, since they are the only notebook company I know
> that positions its output voltage when connected).
>
> c. If the communications protocol needs to announce the power capability of
> the AC adapter, it can do so in a number of ways (by either static or
> dynamic signaling, via either the ID pin or the VCC mains). We don't really
> even need an ID pin to confirm basic power capabilities.
> One area that has not been confirmed is the need to build UPAMD around
> infinite gradients of power capability; I agree that a static analog ID is
> going to have problems discriminating a 53watt adapter from a 54watt
> adapter. But if we believe that a finite set of power capabilities (eg, 20w,
> 40w, 65w, 90w, 130w) then an analog method will be sufficient (we only need
> the equivalent of a 3 or 4 bits of data).
> HP Smart actually becomes digital (low impedance to VCC) at the power
> limit, so an arbitrary power capability can be messaged. If we want
> messaging of a change in power capabilities we could achieve this
> dynamically thru the same analog signal.
>
> d. There is nothing to prevent digital communication on the same path as an
> analog descriptor. A pullup is a pretty benign thing on a digital path.
>
> I laughed out loud when I saw Garry's mail (that 'a resistor and a wire are
> a big deal'). I think Garry has been spying on emails with my marketing,
> who have perpetually questioned any value towards even our 10 cent solution
> in HP Smart. To a degree, I cannot argue with my marketing's argument
> against a "scale of dis-economy;" meaning, volume never erases the cost of
> real material. I am not HP's AC adapter purchasing or development engineer,
> but I can tell you exactly how many cents we pay for the connector and wire.
> I can tell you as well the increased failure rate in the field by just 1
> added wire on the connector. Pretty much the world except for Dell and HP
> don't deploy any kind of ID. Volume cannot erase real costs for copper,
> epoxy and silicon.
>
> The truth is that unless I can prove to my own marketing that we've
> enabled a really compelling feature for the AC adapter, I will be unable to
> get their support for the UPAMD effort. What can we do to make a convincing
> story that we've been sensitive to the value requirements of mainstream
> consumer products ? Lee
>
>
> -----Original Message-----
> From:
upamd@xxxxxxxx [mailto:
upamd@xxxxxxxx] On Behalf Of Edgar Brown
> Sent: Monday, December 13, 2010 12:03 AM
> To:
upamd-comms@xxxxxxxx> Cc:
garrytomlins@xxxxxx; Piotr Karocki;
upamd@xxxxxxxx; Leonard Tsai
> Subject: Re: Simple analog signaling for an AC adapter
>
> As an analog and mixed-mode designer I learned quite some time ago that it
> is preferable not to use an analog system when a digital one can do a better
> job. Tolerances, repertoire of possible responses, long time constants, and
> safety are all rather easy to handle and expand through digital means, but
> can become very complicated and costly through analog ones. My fears in
> allowing for a completely analog 'communications' system to coexist with a
> digital one would be:
>
> (1) we compromise overall safety
> (2) we make it harder to satisfy the stated goals (e.g., life expectancy of
> standard, adapter/device compatibility over life of standard, and
> certification support)
> (3) we could be hindering standard adoption rather than promoting it.
> (4) we might have to create a full digital communications standard from
> scratch (thus increasing overall cost)
> (5) we would be increasing the cost of adapters and devices that wish to
> implement the digital parts of the standard.
> (6) we could be limiting what can be accomplished by the digital
> communication system (e.g., speed, compatibility)
>
> We have to keep in mind the point that Leonard and Piotr have made, once
> devices and adapters are being produced in quantity, the differential cost
> between an analog method and a digital one will mostly disappear. At that
> point, all adapters and devices will have to keep around analog
> communications subsystems just to remain compatible, with no real added
> benefit.
>
> I would expect the cost curve to follow the same adoption path as many other
> technologies (1) first the high-cost high-margin devices will adopt the
> standard (for which functionality would be key), (2) added-value multi-port
> adapters will follow suit, (3) both of these will create a market for ICs
> and off-the shelf subsystems for UPAMD thus reducing implementation costs,
> (4) lower cost devices and adapters will start adopting the standard. I
> would expect such adoption curve to be followed with or without analog
> communications, and I actually see that requiring analog communications as
> part of the standard could hinder rather than accelerate adoption.
>
> Although I can see how a purely analog system can work, I cannot see how it
> can easily satisfy goal 5 (higher power applied only when it is safe to do
> so); goal 4, as the aging of analog components will make it harder to
> guarantee safety or compliance for the life of the adapter; or goal 6, as
> the certification of analog systems across age and component variations
> would become harder to accomplish. (An example that comes to mind is the
> UCD9248 IC from TI, as it states in its errata that it cannot reliably
> identify a considerable section of its address range because it relies on
> resistors and analog values to set it.)
>
> Gary and/or Arjan, can you come up with a more fleshed-out proposal on
> alternatives for how this analog communications would work? A reference
> design would be ideal, but at the very least it should attempt to address
> safety and digital communications compatibility.
>
> For the sake of argument, if we assume that digital communications would be
> following a differential CAN standard over a separate pair, what
> modifications would be required to make analog communications work?
>
> We can discuss on this Tuesday's communications subgroup meeting.
>
> Edgar
>
>
> On Dec 8, 2010, at 8:00 PM, <
Leonard_Tsai@xxxxxxxxxx>
> <
Leonard_Tsai@xxxxxxxxxx> wrote:
>
>> Coming from ODM point of view, the digital communication cost will
>> disappear
>> fast than you expect. Most of the power adapter today already include
>> digitally control IC. Adding an interface of digital communication channel
>> may increase small $ in the beginning but will disappear once healthy
>> competition starts.
>>
>> Analog way is a bigger problem as it creates testing requirement for
>> production line and room for error.
>>
>> Leonard
>>
>> -----Original Message-----
>> From:
upamd@xxxxxxxx [mailto:
upamd@xxxxxxxx] On Behalf Of Tomlins, Garry
>> Sent: Wednesday, December 08, 2010 8:20 PM
>> To: Piotr Karocki;
upamd@xxxxxxxx>> Subject: RE: Simple analog signaling for an AC adapter
>>
>> I agree with Lee and Arjan:
>> This is heading down a path of unnecessary and complex functionality that
>> leads in turn to a complex and expensive implementation. I beleive it will
>> not be attractive to the major equipment ODM's who will need to adopt this
>> if
>> it is to be a success.
>> We should have a simple analog low cost option.
>> In my experience in servicing the adapter market for high volume
>> electronics
>> adding a pin, a wire, a resistor a pin to an IC is a big deal - let alone
>> a
>> separate communications system!
>> My vote is for a simple analog option as described. I believe this will
>> have
>> a good chance of adoption and would be a success for the project.
>> Garry
>>
>>
>>
>> Texas Instruments (Cork) Limited, Registered in Ireland under Registration
>> Number: 294554, Registered Office: Riverside One, Sir John Rogerson's
>> Quay,
>> Dublin 2
>>
>> -----Original Message-----
>>
>> From:
upamd@xxxxxxxx [mailto:
upamd@xxxxxxxx] On Behalf Of Piotr Karocki
>> Sent: 08 December 2010 11:50
>> To:
upamd@xxxxxxxx>> Subject: Re: Simple analog signaling for an AC adapter
>>
>> I don't agree with Arjan.
>>
>> We could either "describe current situation" or "shape the future".
>>
>> Our standard could allow resistor-based "communication", something,
>> something, and full communication (required voltage etc.).
>> But as one of goals is to allow to connect every device to every supply
>> (and,
>> in near future, connections in form of grid; power hubs, power storage
>> etc.),
>> every supply has to have full communication option. Making provision to
>> understand simpler communication (as resistor based) makes supply more
>> costly.
>> Say, we have hundred million devices. Half of them - resistor based
>> communication, and tenth of them - full model of communication (4/10 of
>> them
>> some 'in-between' form).
>> Or, we could force whole 100 000 000 devices to have full model of
>> communication.
>>
>> But it is the only way to make this full communication cheaper - as it
>> would
>> be "more mass" production. It would be ONE standard...
>> And the only way to make possible to connect device from 2010 to power
>> supply
>> from 2050 or vice versa. This scenario is not impossible - when standard
>> becomes "grid version"... How often you change wiring in your house?
>>
>> ________________________________
>> From:
upamd@xxxxxxxx [
upamd@xxxxxxxx] On Behalf Of arjan strijker
>> [
arjan.strijker@xxxxxxx]
>> Sent: Wednesday, December 08, 2010 12:26 PM
>> To: Atkinson, Lee; Bob Davis;
upamd@xxxxxxxx
>> Subject: RE: Simple analog signaling for an AC adapter
>>
>> I agree with Lee that UPAMD should also support low cost devices.
>> A simple resistor to ground inside the device could tell the adapter what
>> voltage it requires.
>> More sophisticated device can still do power negotiation etc.
>>
>> With regards,
>> Arjan Strijker
>>
>> From:
upamd@xxxxxxxx [mailto:
upamd@xxxxxxxx] On Behalf Of Atkinson, Lee
>> Sent: Wednesday, December 08, 2010 12:08 AM
>> To: Bob Davis;
upamd@xxxxxxxx>> Subject: Simple analog signaling for an AC adapter
>>
>> Bob, here is a quick presentation on the method that HP uses for
>> signaling from the adapter to the notebook. We've had this system in place
>> since 2005 or 2006, and have shipped maybe close to 150million systems
>> that
>> use the common "HP Smart" system (including notebooks, all in one
>> desktops,
>> and small form-factor desktops).
>>
>> My suggestion is that we at least baseline a system that will allow
>> some
>> scalability of the communication method; at least, allow very low cost
>> devices to connect to a UPAMD power source and work reliably even if their
>> functionality is limited. I'm not sure that a lot of simple devices that
>> would use UPAMD have a need for all the messages that the adapter could
>> provide, or would be able to negotiate variable power consumption. I think
>> we
>> all agree, there is very little precedence for using sophisticated
>> signaling
>> in the common DC powered devices now in the market. Though I agree the
>> simple
>> methods are limited, if we can deliver a scalable solution there will be
>> fewer reasons for the industry to not adopt UPAMD.
>>
>> Thanks again--Lee
>>
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