[0x402DF854]

You are indeed missing something here :)

Long 1-wire networks are notoriously unreliable [1]. Something that works fine today can stop working tomorrow. That doesn't mean that they shouldn't be used anywhere. They have their niche.

If I want my heating system monitor to report temperatures once per hour and it takes me 5 tries and 10 seconds to read a sensor, I call it good enough. If monitor doesn't succeed after 20 retries, it sends an alert to replace the sensor (so far that only happened due to damaged wiring, not the sensor itself).

It is possible (and quite fun) to build reliable systems using somewhat reliable components :)

[1] https://www.maximintegrated.com/en/design/technical-document...

[metaphor]

Thanks for the perspective. 2 points in which I disagree: on design and on reliability.

First, on design. In your cited app note, Maxim explicitly denotes from the onset:

> Operating a 1-Wire network beyond the limits or disregarding advice given in this document may result in unreliable network performance.

The key operator that I see here is "beyond the limits", to which Maxim engineers appear to have done a fair job of specifying. Indeed, there's a lot of fine print in the published datasheet[1] alone on "parasite power mode", but a first pass suggests this is nothing more than a nuanced design challenge, not one of questionable reliability. If your long 1-wire network works today but not tomorrow, then it's difficult to swallow attribution of the issue to a singular authentic component constrained by documented performance specs rather than the system's overarching design.

Second, on reliability. Since practicing engineers don't have the leisure of independently validating every bit of specified electrical minutae, we generally have to extend some level of trust to what the component vendors specify in datasheets unless presented with evidence to the contrary (because bugs). I poke fun at your "works fine" remark above because it reads like what you care about is some semblance of establishing trivial, intermittent communication while handwaving the accuracy of the reported temperature measurement, especially given all the effort to demonstrate and document that the physical implementations of these counterfeits are clearly different...which renders the reference datasheet null and void in its entirety...which I therefore conclude nothing about these counterfeit sensors can be trusted in any application with meaningful skin in the game. To describe these counterfeits as "somewhat reliable" strikes me as somewhere between naively optimistic and outright delusional.

But hey, your hardware, your problems...just saying. :)

[1] https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf

[0x402DF854]

I am having troubles understanding your reply. You're saying that these counterfeit sensors cannot be used for anything critical with "meaningful skin in the game", which is an obvious statement. In fact, depending on definition of "critical" and "skin in the game", one can make an argument that authentic DS18B20 sensors also aren't good enough. So what?

This whole story about not using things where they shouldn't be used is like saying "don't use an arduino on a chemical plant". Thanks, we get it.

> The key operator that I see here is "beyond the limits", to which Maxim engineers appear to have done a fair job of specifying

Except that limits are not well specified since they depend on too many factors (ambient temperature, parasitic cable capacitance, noise pickup, etc). These are recommendations on improving reliability, not hard guarantees. I'd recommend actually reading that note.

> If your long 1-wire network works today but not tomorrow, then it's difficult to swallow attribution of the issue to a singular authentic component constrained by documented performance specs rather than the system's overarching design.

This is again a trivial statement. Where did I claim the opposite?

If a weather monitor equipped with 1-wire devices has intermittent communication issues, do you immediately replace the entire system? Good luck with that proposal :)

If you replace your 1-wire driver on the above mentioned system to the one with active pullup and issues go away, do you still scrap the system because it's "out of spec" according to recommendations?

> Since practicing engineers don't have the leisure of independently validating every bit of specified electrical minutae, we generally have to extend some level of trust to what the component vendors specify in datasheets unless presented with evidence to the contrary (because bugs).

Again not sure what's the point of this trivial statement. Yes, bugs. I, "practicing engineer", have the leisure to independently validate datasheets when required. I also rely on them when I can. So what?

> especially given all the effort to demonstrate and document that the physical implementations of these counterfeits are clearly different...which renders the reference datasheet null and void in its entirety...

I invite you to research re. FDTI-gate and its widespread use, including medical devices.

Are you comfortable using light bulbs purchased from amazon in your kitchen without looking at the reference datasheet?

If I need an accuracy of +/- 5 degrees for not critical monitoring purposes, can I use "counterfeit" DS18B20 sensors?

If I need an accuracy of +/- 0.1 degrees for critical monitoring purposes, can I use "authentic" DS18B20 sensors?

Answers are as obvious as your statement.

> which I therefore conclude nothing about these counterfeit sensors can be trusted in any application with meaningful skin in the game

Your subjective "meaningful skin in the game" doesn't tell much. What sensors do you trust? Do you require calibration certificates traceable to a secondary standard for each component for them to be blessed for "application with meaningful skin in the game"?