According to net Raspberry Pi is like a tiny, cheap,affordable for everybody computer.It includes all
the components of a standard PC (processor,memory, USB ports, etc.), can run various operating systems
and can be used in many projects (desktop usage but also electronics, robotics, retro-gaming,
useful in large and small industries).It also has very low energy consumption.
Let's try to examine what is claimed one by one.
"Tiny": well I would say "small" compared to a motherboard of the same production year since you cannot
compare a Pi with a desktop computer or laptop box.That said leaving out the extra capabilities (many
times more) and extra hardware that a modern motherboard has.But just moment THINK:is it really small
compared to an average smartphone?Isn't a smartphone a tiny enough computer?The fact that it has
proprietary device drivers does not have an impact in its size.
"Cheap,affordable for everybody":You can certainly buy a 5 years old computer for the same price
(or get it for free), having more capabilities.Don't forget Pi has no peripherals.
"Computer":Yes,you can say this.But,what a user (even experienced one) has in mind or is accustomed to
when buys a product? Probably that someone else took care for its physical properties.Imagine Pi
connected with at least four cables (keyboard,mouse,HDMI and power) physically heavier and tougher than itself.
Mess!! How many people use a motherboard with out a box?
Cases and hats don't help too much either as they are light and completely useless if you try to connect an extra or
a custom hardware(s).
The above do no apply if you are going to use it headless in a FRIENDLY environment (e.g. home small
server). By the way this is probably the most useful thing Pi does.
"It includes all the components of a STANDARD PC":I shall not go deeper here.Simplification ,easily leads
to a point saying nonsense.
"can run various operating systems":NO.Despite claims,it runs only Linux operating systems.Perhaps
it is harsh (sales wise) to clearly state that it cannot run these "other" operating systems.Customers must
learn this "the hard way".
If someone needs full Linux power try booting Arch Linux or maybe a dual boot? but this not for the fainthearted.
"desktop usage":NO,see above.
"electronics usage":Possible,Personally I can't see any relative advantage other than it is cheap enough
to destroy,it can work offline with batteries (more off this later) or because of GPIO pins,
(supporting various communication protocols).
By the way do you know that with a simple parallel port (remember them?) you can control eight
input-output plus four input devices?Serial can do this also but with a much more difficult interface.
"robotics":Possible,in toy machines in education (can work offline). Specifically Linux has
a drawback here, most first-middle level education uses Windows.This is not a big problem since these
projects usually use high level programming languages.
Although Pi is capable to move a large CNC machine, since the machine doesn't care a lot for computer's
speed (the main problem of the designer is inertia of moving parts and high currents),it (Pi)
lacks a lot of ram and CPU for the design process of the product the machine produces.
"retro-gaming":Sure,the only gaming can handle.
"useful in large and small industries":There is absolutely no business man that will use Pi, no
matter what.No one is willing to depend its production line to an employee or two who "hacked" or designed
something using Pi or something like Pi.
If he does, he will discover why in the future "the hard way", no matter what happens,or whose fault was.
For simple machine alterations (e.g yes or no decisions) there are companies (e.g.SIEMENS)
which offer devices (microprocessor + hardware interface + easy programming platform) that
the local technician can handle.These (devices) usually are expensive,but business people don't care either way
because they are only conscious for the rate of return.
Small and large industries buy machines (hardware+software)from machine manufacturers.
In their turn assign to a different department or to another specialized company the software creation.
Small machines use microprocessors now days (even if they don't need them), large ones high-end computers both with
proprietary software having 1 or 2 years guarantee and a maybe 10 year support period.
After that the machine no matter its initial cost or its condition goes to scrap (no support),or sometimes sold
at a very depreciated value.There might be a few exceptions though.
I have countless,sometimes funny,storiesconcerning above.
I"ll stop here...
"low energy consumption":Certainly it is a low power device.It cannot be considered "green" since
nobody will leave the convenience of a full feature PC for a Pi.Again,compared to a smartphone is
lacking efficiency.Even if its consumption (when in line) is translated from a few cents to
1$ or 2$ per month working 24/7 (depends on the model),this deficiency (compared to a technological
advanced smartphone) plays a tremendous role when powered from batteries.
First of all Pi lacks a "watch-dog" feature (no-no,not the watchdog application).
This feature has to do with CPU architecture and Pi's "BIOS",putting CPU in a deep "sleep" mode,
having the least possible cycles,and providing an external interrupt that wakes up CPU.
Another problem is 5v power supply.Although we are able to produce transistors with very low
collector voltages (which by the way this is a nightmare for poor hobbyist and many professionals)
engineers keep the standard nominal ~3.6v supply for mobile devices (lithium Battery).
That said,one has two (at least) options.Use a buck regulator and at least two batteries
in series(the other being series/parallel) or boost regulator with batteries in parallel.
Buck regulator usually have better efficiency but you must add considerable amount of electronics
to charge batteries (if not willing to remove them every time need charging).
Personally I prefer a boost converter for the case.Tried several of them (even a discrete one)
I could not reach more than 75% efficiency decreased to 70% in full current.
Advice:Don't trust claimed efficiencies.They always talk for ideal conditions (if not cheating).
As a result,there is a lot of wasted energy before even supplied to Pi.
On the contrary Pi has a nice feature.You can easily turn off Ethernet port (if exits) which
consumes a considerable amount of energy.Unfortunately this turns off the whole internal boost
regulator (probably) so turns off USB ports also.
A few words about WiFi:Although the name Broadcom brings me memories of terror from the early
Linux WiFi era the card and driver seems to work O.K.I would prefer though a chipset that supports
monitor mode also.
Concluding,my belief is that most of these nice,small,underdeveloped computers end up in the drawer a few weeks time
(if not earlier) after the date of purchase.The sales rate doesn't change my opinion.
This is not to say is useless,after all, there are only a few options for well supported pure Linux small boxes capable of going mobile.
Regards