Thanks for the words. But, I think my days are numbered here.
Gerald
That’s a shame. Truly. You’ve contributed much in the last several years since the original beagleboard. I can imagine without project like this that many other boards like the nVidia Jetson K1 would not be available.
But . . . I think I understand where you’re coming form. Aside from the thanklessness.
When you design low cost hardware, you have to make certain decisions to
get the cost down.1) As few components as possible.
granted, no problem with that.
2) Limit the application. Only one application,
do we know what the application is? Apparently people tend to think
that this can do anything.
3) Push as much cost outside, for example the power supply.
hmmm, then that says you have not as much control over the power
supply as you might want. Certainly not as much as you may like.
4) Lowest cost components.
no problem.
5) Limit the features.
no problem. It does what it does.
6) Cut the profit.
diminishing returns.
Yes, there are several things I could have done different. Many of these no
one has even identified.
Perhaps it might be interesting to know what they were... Not
criticizing, but to know design alternatives might be nice.
But if I had, you would not have bought it because
it cost too much. After all hardware is supposed to be cheap.
I'd personally disagree. Hardware costs as much as you pay for, and
does what you design it to do. I, for one, am willing to pay more for
more capability, within reason. Not your typical consumer,
though.....
That is where
the value is, in the price. Not the value..
Then you're designing to a price point, and that's a different thing
entirely.
Nobody asked how I took it from $89 to $49. They just bought them up and
complained that it didn't do all the things they wanted it to do for $49.
I'm not even aware that your initial design was 89 dollars. I might
not have bought it for that, but that would have been my decision. "I"
however, am not "they".... but there are a lot more of "them" than
there are of me....
Not practical for you to put too many blank pads on a board and expect
the user to solder parts in. I do, because I can build the boards.
Your average hobby type... not likely I suspect.
If anyone of you want to change the design, add more features, make it more
robust, add more cost, increase the price, manufacture it and sell it, by
all means, go ahead. I am sure there will b a few folks that value the
hardware and recognize that value, and will pay for it.
If I needed something with that capability, I'd probably buy it
because my cost preference on a PC board is 2 layers and not 4 or 6. I
don't have the money to develop a product at this level, nor do I have
the desire, nor perhaps the time or expertise.
The cost would, of course, determine how many I'd use, and for what,
but that's a simple economic decision. Then there's the engineering
decision.
But, I suspect the majority will complain that it is too expensive and will
stay with the BBB and instead ask how to flash the latest image in the BBB
and why does my my GPIO does not work..
Can't help you with that....
Harvey
@William
The part I was referring to is your constant need to second guess peoples motives and intentions. This is an open forum and developers are always welcome to provide their input. I don’t know why you constantly have this compelling need to denigrate people on this forum. Gerald doesn’t need you to protect him. He is more than capable of defending himself and his product. I acknowledge your contributions to helping people on this forum, but it pisses me off when I see you tear into people for no apparent reason. Stay away from the personal stuff.
Regards,
John
HI Harvey,
I’d personally disagree. Hardware costs as much as you pay for, and
does what you design it to do. I, for one, am willing to pay more for
more capability, within reason. Not your typical consumer,
though…
Id disagree with you. Only because we can second guess each other until the end of time. But the point here that this was part of the reasoning for the design behind the BBB, and without it we would not be where we are.
I’m not even aware that your initial design was 89 dollars. I might
not have bought it for that, but that would have been my decision. “I”
however, am not “they”… but there are a lot more of “them” than
there are of me…
The initial design discussed here is the BBW I believe. By the time my biddy and I priced the BBW actually, the cost was $99.
If I needed something with that capability, I’d probably buy it
because my cost preference on a PC board is 2 layers and not 4 or 6. I
don’t have the money to develop a product at this level, nor do I have
the desire, nor perhaps the time or expertise.The cost would, of course, determine how many I’d use, and for what,
but that’s a simple economic decision. Then there’s the engineering
decision.
Problem is, if this design was only a 2 layer design. the actual board dimensions probably would have increased 5x or more.
But, I suspect the majority will complain that it is too expensive and will
stay with the BBB and instead ask how to flash the latest image in the BBB
and why does my my GPIO does not work…Can’t help you with that…
If you want my take on this situation . . . it’s because the I.Q. of the average person posting on theses forums seems to have diminished in the last couple of years. These people can not understand that the software people on this project are not paid and offer their service for free to the community. As well as software upgrades are not the responsibility of the community, nor are these upgrade required for the software that third parties have written to work properly. Nor, do these third parties take responsibility for doing so . . . I could go on all day . . .
And, of course, I’m sure John has something to say, about what I have to say. Good thing for me, and everyone else who reads these posts. that I have blocked his posts on this forum. Globally.
You cannot get the board layout done with 2 layers and you would have all kind of issues with power supply noise, ground bounce, etc. You have to start with 2 power planes and then you need at least 4 layers to get the signals out from the processor. You will not be able to route the board on 2 layers. You need a minimum of 4 routing layers and add 2 power planes and so you have a minimum of 6 layers.
Regards,
John
HI Harvey,
I'd personally disagree. Hardware costs as much as you pay for, and
does what you design it to do. I, for one, am willing to pay more for
more capability, within reason. Not your typical consumer,
though.....Id disagree with you. Only because we can second guess each other until the
end of time. But the point here that this was part of the reasoning for the
design behind the BBB, and without it we would not be where we are.
It's not second guessing. We're (to me) looking at different design
goals. I'm willing to pay more to have a feature if I want it. Price
point is simply that, 5 more dollars and who knows how many customers
you lose?
Because I design *my* stuff (to my own price points....) it's a matter
of divergent design goals. Not right or wrong, just different.
I'm not even aware that your initial design was 89 dollars. I might
not have bought it for that, but that would have been my decision. "I"
however, am not "they".... but there are a lot more of "them" than
there are of me....The initial design discussed here is the BBW I believe. By the time my
biddy and I priced the BBW actually, the cost was $99.
Ah, now that is a different product. Different design goals.
If I needed something with that capability, I'd probably buy it
because my cost preference on a PC board is 2 layers and not 4 or 6. I
don't have the money to develop a product at this level, nor do I have
the desire, nor perhaps the time or expertise.The cost would, of course, determine how many I'd use, and for what,
but that's a simple economic decision. Then there's the engineering
decision.Problem is, if this design was only a 2 layer design. the actual board
dimensions probably would have increased 5x or more.
properly. With added layers, there's a factor that makes the board
more stable, gives better performance (due to transmission line
effects and signal isolation), and is often easier to route in a
particular size. The physical cost is that the board can cost twice
as much (at least).
But, I suspect the majority will complain that it is too expensive and will
stay with the BBB and instead ask how to flash the latest image in the BBB
and why does my my GPIO does not work..Can't help you with that...
If you want my take on this situation . . . it's because the I.Q. of the
average person posting on theses forums seems to have diminished in the
last couple of years. These people can not understand that the software
people on this project are not paid and offer their service for free to the
community. As well as software upgrades are not the responsibility of the
community, nor are these upgrade required for the software that third
parties have written to work properly. Nor, do these third parties take
responsibility for doing so . . . I could go on all day . . .
I think that the BBB has transitioned from a somewhat specialized
product supported by hobbyists to a commodity. Commodities are bought
by appliance users (a term borrowed from the amateur radio community).
The mindset is quite different. The expectations of the consumer are
also quite different.
If you think the BBB is bad, I think we should both consider the
Arduino world....
Harvey
You cannot get the board layout done with 2 layers and you would have all kind of issues with power supply noise, ground bounce, etc. You have to start with 2 power planes and then you need at least 4 layers to get the signals out from the processor. You will not be able to route the board on 2 layers. You need a minimum of 4 routing layers and add 2 power planes and so you have a minimum of 6 layers.
I wasn't considering a modification of an ARM design, I was thinking
more of different processors. My preference (and cost limitations) as
well as what I already have software for, point me to other
processors. If I were to use ARM processors ( a possibility), I'd be
working with a pre-made board of some sort, due to manufacturing
difficulties.
Harvey
It’s not second guessing. We’re (to me) looking at different design
goals. I’m willing to pay more to have a feature if I want it. Price
point is simply that, 5 more dollars and who knows how many customers
you lose?Because I design my stuff (to my own price points…) it’s a matter
of divergent design goals. Not right or wrong, just different.
Ah, ok, I get that.
Ah, now that is a different product. Different design goals
Absolutely. The BBW for us would have worked fine, but many of the cool features like onboard JTAG simply was not needed for our design goals, but seemed to have added a lot of costs that we would have preferred not to pay. So for us, in this context, Gerald was bang on with his designed goals. But was it perfect ? Probably not, but how many here would profess to “looking a gift horse in the eye” ? Also, many of use could look at these so called design flaws as an opportunity. I’m already making money from one such “flaw”, that is actually not a flaw. But a design / cost decision.
From my experience, perhaps a factor of 2 IF the board could be routed
properly. With added layers, there’s a factor that makes the board
more stable, gives better performance (due to transmission line
effects and signal isolation), and is often easier to route in a
particular size. The physical cost is that the board can cost twice
as much (at least).
Well my own comments here were rather . . . yeah I do not know what. I’m not an EE, with experience in design layout. But I do have some understanding of the process, as one of my long time friends is very good with orcad, and design layout. So, I’m sure there is more than dimensions to consider in this design. For instance, I know that the DDR traces have to be very exact. A two layer design would surely have an impact on that, if not more . . .
I think that the BBB has transitioned from a somewhat specialized
product supported by hobbyists to a commodity. Commodities are bought
by appliance users (a term borrowed from the amateur radio community).
The mindset is quite different. The expectations of the consumer are
also quite different.If you think the BBB is bad, I think we should both consider the
Arduino world…
I do not know much about the Arduino world. I prefer not to think about Arduino’s period. My buddy here who is a very good EE, and has been an EE for 35+ years tells me he thinks the Arduino is awesome. Because it puts hardware in the hands of novices, and give them the ability to “make”. My take on this is quite the opposite actually . . .
But here is the thing, 3.5+ year ago I entered into the world of Beagle knowing nothing. So I can understand the frustration of not knowing how to deal with a given situation. I have even once or twice “bitten someones head off” because I was frustrated. The thing is, my inability to understand something is not someone elses problem, or responsibility. Which I realized even as I complained silently to myself . . .so I forced myself to learn, instead of blaming someone else for my inabilities. Now, I understand more about this hardware, and perhaps a good bit more about embedded Linux. But ONLY because I put effort into it. Well, others have helped some too, but no one did anything for me. Others helped as I helped myself to learn enough to ask a smart question.
Honestly I think I can count the “real” questions I’ve asked on these groups on one hand. I’ve asked Robert many questions in relation to other posts he replied to from others. But questions I started myself . . . very few. So why is this important ? It’s important because 99% of the time it’s best to go out and find the answer for yourself, and make sure you get the correct answer. Versus getting the wrong answer right away from someone else. There are of course exceptions, such as asking Robert specific questions about things in his domain. Not only that, but going out and finding your own answers sets you up as a problem solver. Someone who can think their own way out of things, versus being a hindrance on the community.
Anyway, this all ties to people making false assumptions on these groups and getting huffy / puffy, and claiming that x.y.z platform is better because of a.b.c. But guess what ? Beagle hardware has no direct comparison out there. So if peopel in this situation do as they claim, they’re only hurting themselves. Most of these people though , , I tend to view as dim witted want-to-be’s. People who want to run a media player app/ shell / whatever, and nothing else WHICH, in this persons humble opinion is not where this hardware shines . . .anyway, I’m starting to rant. Perhaps I should call it quites for now.
By the way, Happy 4th to all you ‘Merican’s’ of which I am one too 
John Syne writes:
a power supply that is spec’d at 4A should not shutdown when it sees a 4A load, but rather, it should current limit at 4A. If the power supply is spec’d at 4A, then 4A should not be treated as a short circuit.
That’s impossible. You can’t recommend that fundamental electrical laws be overridden. 
If a PSU current limits at 4A, it can do so only by reducing its output voltage. This may then drop below specification for its load and this can have very bad consequences such as non-stop rebooting. There is no way for the voltage to be maintained above its minimum spec while still providing a current limit.
This is the reason why ensuring that startup inrush transients cause no harm must always be handled within the design of the load, ie. the BBB in this case. The load is a black box as far as the external PSU is concerned, so the external PSU has no means to perform this protective function while still maintaining regulation. (Blowing a fuse does not maintain regulation, but is sometimes the only practical alternative.)
In other words, a load can demand a minimum current capability under a rated voltage specification, but it cannot demand a maximum current capability unless it can cope with arbitrary drops in supply voltage. Such voltage tolerance is generally not available in electronic circuitry today, certainly not in BBB.
Nonsense. This is how the vast majority of power supplies work. The voltage ramps up while the current is maintained at it’s maximum current. When the voltage reaches the regulation voltage, the current is reduced. What the OP proposed is that 4A was regarded as a short circuit and hence the power supply shutdown. This is not normal.
Regards,
John
I’ve often wondered how many people post in here trying to be seen as knowledgeable. Great comments William
Nonsense. This is how the vast majority of power supplies work. The voltage ramps up while the current is maintained at its maximum current. When the voltage reaches the regulation voltage, the current is reduced. What the OP proposed is that 4A was regarded as a short circuit and hence the power supply shutdown. This is not normal.
Much of this depends on the type of supply.
A bulk supply provides unregulated current to the limit of its
capacity. Voltage decreases as current is drawn. There are no
voltage or current regulating elements. Obviously not used for the
BBB.
A voltage regulated supply may or may not have a current limit
circuit.
If not, then the supply current is limited by the resistance of the
parts. From zero, the supply will try to charge up whatever
capacitance is on the output. Large startup currents can happen,
similar to a bulk supply. The voltage regulator does keep the output
voltage from rising past a set point, however.
A voltage and current regulated supply may operate in two ways
depending on the current limiter design.
If the supply is only current limited, then the supply is a constant
current supply at startup, supplying the maximum current it can
(depending on load) until the nominal voltage is reached (assuming
we're charging capacitors). Under normal operation, the supply is a
voltage regulated supply. Should current demand exceed (or try to)
the current limit, the supply becomes a constant current supply. The
voltage drops to the point where the rated maximum current flows.
For instance, 5 volts 4 amps. Put a 2 ohm load on the supply and you
have 5 volts at 2.5 amps load. Put a 1 ohm load on it, and you will
have a 4 volt supply at 4 amps.
It is possible for a supply to have foldback current limiting. In
that case, the maximum supply current changes on maximum draw. In
this case, you may have a 200 ma current foldback limit. Try to draw
4 amps and the supply changes its limit to 200 ma and adjusts the
output voltage to maintain that lower limit. Depending on the design
of the foldback, the load may have to be reduced or disconnected to
restore the regulated voltage.
Constant voltage with constant current limiting is common on lab
supplies, higher quality wall-wart power supplies, and is not common
on straight battery supplies, or bulk supplies, and some older (and
cheaper) power adaptors.
Power limiting can be built in rather easily, though, if you have the
right parts.
Harvey
John Syne writes:
Nonsense. This is how the vast majority of power supplies work. The voltage ramps up while the current is maintained at it’s maximum current. When the voltage reaches the regulation voltage, the current is reduced.
How? By magic?
You appear to think that current limiting “just happens”, without understanding how it’s actually done. It cannot be done without affecting the supplied voltage, as that is core electrical theory.
It doesn’t matter how a PSU implements current limiting internally. It could be manipulating effective internal resistance with linear devices, or it could be altering buck/boost frequencies or duty cycles, or it could be controlling linear or packetized charge injection into a capacitive tank, or in a fun Heath Robinson world it could even be using stepper motors to switch between transformer or inductor windings, but it really doesn’t matter how. Regardless of the internal technique in use, the end result is that when the current limit is reached and fractionally exceeded, the PSU will always and under all circumstances reduce the voltage supplied to the load that is demanding the excess current. There is no alternative available in circuit theory.
And if the load keeps on demanding more current, that supply voltage will keep on dropping, until it goes out of spec and then “bad things happen”.
You won’t understand this until you check it out yourself — easily done, just grab a programmable PSU, set a current limit on it, watch the voltage on a separate DVM, and reduce your load resistance to demand more current. Good luck trying to keep the voltage fixed when you hit the current limit. Not gonna happen. 
Incidentally, it’s very important that you try this and understand it. Nothing in electronics will make any sense to you until this is fully comprehended, as it’s such a fundamental part of circuit theory.
Perhaps a poor choice of words . . .but both definitely know more about power electronics than I. Which I’m afraid isn’t saying much.
Clearly you are not listening. I already said the voltage will drop and then rise as the capacitor charges, but the current will be constant until the voltage reaches the regulator voltage. All these references to all kinds of power supplies is senseless. We are only talking about the 5V2A supply recommended for the BBB, or the 5V4A supply suggested by the OP. If the power supply is spec’d at 2A, you are not going to get 10A because the power supply will protect itself and reduce the voltage to maintain the 2A limit. If this protection was not available, the power supply would just die. Your argument is this is a 10Watt supply, so if you drop the voltage to 0.1V, you can achieve 100A make no sense whatsoever. The maximum current is defined by the size of the wire in the coil or transformer and the size of the PCB traces. To prevent exceeding this max current, the regulator will reduce the voltage and maintain a constant current, thereby protecting the power supply from a dangerous failure.
Regards,
John
John, thank you for your feedback!
Looks like the central question what is the “correct power supply”, moreover what is the standard to protect from overcurrent by power supply.
1). Oldest method is: fuse.
2). Old method is: if the load heavy than power supply capability then limit current to maximum (decrease output voltage).
3). if the load heavy than power supply capability then decrease output voltage using diffrent characteristic.
4). If power supply detect overcurrent, then switch of output voltage for specifyed time and then try it again.
Next question is: how long overcurrent is overcurrent?
a). Overcurrent for 1ms?
b). Overcurrent for 100ms?
c). Overcurrent for 1s?
Present method used by BBB is match just for power suppy which use method 2b and c.
That is why I say, moving “CAP” from TPS2051 IN to OUT make board compatible power suppy which use method 1-4 (near all).
But the main probelm is: manufacturers not specify what is the current protection method for its power supply. Therefore you cannot select “correct power supply” which use method 2.
Othersides I understand your cost problem. But current board has enough space to place one more 10uF 10V capacitor (see C7, C8, C10, C13). And it is cost less than 0,01USD. I think is this worh for mouch wide power supply compatbility.
Yes, but remember that the problem here is a startup inrush current,
which would be handled properly by current limiting. After all, that's
what the 2A current supply is doing: essentially, it soft-starts,
providing limited current charging the input caps, while ramping up
the voltage. Once the caps are charged and the supply voltage
stabilizes at the nominal value, the system progresses to boot.
Your discussion makes the assumption that the power supply provided or
specified is current limited at the maximum output current. I
(without looking at PS specs) have no such assurance.
*with* such limiting, behavior is one way. Without that limiting,
behavior is quite something else.
I don't remember (particularly...) that the power supply specification
mentioned current limiting. I thought that I had read only a voltage
tolerance. People on this forum have mentioned using a particular
supply (not model number, simply rating). The normal problem I have
seen was the current supply rating, so that the BBB could boot as well
as have sufficient power to drive such things as hard drives.
It seems to me that this does not address the *maximum* current of the
supply, nor does it specify what kind of supply is expected to supply
that maximum.
If this current capacity (as in surge current or current limiting) is
a difficulty, then perhaps it needs to be addressed. I have not seen
(nor particularly searched for....) such limitations.
*if* they are important, then they need to be mentioned. If they are
not, then perhaps that needs to be mentioned as well.
Harvey