Re: PCB version control

On 2025-03-26, Don Y <blockedofcourse@foo.invalid> wrote:

On 3/26/2025 12:22 PM, Joe Gwinn wrote:

Form, Fit, and Function is now widely applied:
 
.<https://en.wikipedia.org/wiki/Form,_fit_and_function>

>
It is also how customers think of products.
>
Is your BMW 320i EXACTLY the same as the one that was
parked immediately adjacent to it on the dealer's lot
at the time of sale?  Are you *sure* all of the components
and subassemblies from which it was built are EXACTLY
the same (i.e., same rev levels of same part numbers?).
>
Do you, as a customer, *care*?  Or, do you have a notion
of what a "320i" is and are satisfied that the vehicle
you purchased fits that interpretation?
>
You likely would be upset if told that this particular
vehicle happened to have "rev A" subassemblies in it
while all the other units on the lot were rev B or later.
>
    "Do I get a discount for that?  Or, will you upgrade
    the assemblies to the latest AT NO COST TO ME?"
>
In general, people want the "latest and greatest".  You
sure wouldn't want to buy something with an OLD version
of firmware in it (as newer versions tend to fix bugs in
older versions and/or add features/functionality/performance).
>
In *regulated* markets, you may want to be able to purchase
a specific version of a product -- if only to ensure 100%
compatibility with other instances you'd already acquired.
As such, you want (need!) the vendor to be able to roll
back his CM system to any arbitrary point in time and
create "one of those" (obviously, for some financial
consideration).
>
E.g., in the gaming world, I need to be able to recreate
a particular make/model/*serialnumber* of a built game if
there is some concern that there may be a hardware or
software flaw in THAT particular instance:
     "Serial number 12345 has been paying out at a statistically
     significant higher level than the rest of the herd.  Can
     you explain why?  Was there any change in the production
     of that unit that might be suspect?  We've already
     PHYSICALLY examined the unit for signs of compromise..."
>
The military is particularly obsessive about this sort of thing.
*And*, saddled with older CM technology.
>
A well designed CM system can also be leveraged for marketing
and support purposes.  E.g., I can create a virtual part number
that represents "Joe's 320i" which is little more than a
wrapper around the purchase order he placed -- and delivery
manifest associated with -- for his vehicle.
>
Now, I can issue a query to identify all SALES and associated
customers who happen to have an instance of the vehicle (ANY
vehicle that I may have sold) that uses a bolt discovered to
be defective!  No need to create an entirely different system
to handle such queries!
>
Or, identify sales of vehicles that included navigation systems
so I can pitch a "map update" to them (I surely wouldn't want
to incur the cost of reaching out to folks who purchased
vehicles that DON'T have navigation systems -- the map update
wouldn't have any applicability, there!
>
A sale is just a different type of "relationship" with a
(top level) BoM.  (though I can likewise identify any customers
who purchased "spare parts" that include the items of concern
as well as the vendors f5rom which the parts were obtained)
>

A real example, that caused some pain, was the Raspberry Pi 3B+,
which at some point changed internally from rev. 1.3 to rev 1.4.
Unfortunately this was not made visible on purchase ("It's an RPi
3B+"), and the firmware image we were using wouldn't boot on the
rev. 1.4 hardware.

So, should they have sold the rev. 1.4 3B+ as something different
(3.1B+)?

No idea what changed, but it must have been significant enough
to require a change to the bootloader. I assume (hope) it was a
necessary change, i.e. it wasn't possible to make any more rev.
1.3 parts, and not just tinkering or cost reduction, though I
suspect the latter. In that case we'd happily pay (a little)
more for compatibility :(


--
Ian

"Tamahome!!!" - "Miaka!!!"