USB low level

[Drazen]

Hi everyone, I have to do a strange question about USB interface on P.C.

I should drive a USB port at low level on a P.C. I should drive directly
data signals.
I want to develope an interface that can be connected to a P.C. but also
that can be connected to a controller produced by me without develope the
USB host on my controller.

Someone know if is possible disable an USB port on Windows and use directly
USB signals, maybe whit a direct addressing on the Chipset on the
Motherboard ?

Thanks and sorry for my English.

Drazen.

 

[Ian Stirling]

Hi everyone, I have to do a strange question about USB interface on P.C.

I should drive a USB port at low level on a P.C. I should drive directly
data signals.
I want to develope an interface that can be connected to a P.C. but also
that can be connected to a controller produced by me without develope the
USB host on my controller.

Someone know if is possible disable an USB port on Windows and use directly
USB signals, maybe whit a direct addressing on the Chipset on the
Motherboard ?

Probably the simplest way is to just buy a $several USB-serial adaptor,
and use that.
Any reason why not?
ZZ

 

[Adrian Jansen]

The USB standards committee will not like you.

--
Regards,

Adrian Jansen
J & K MicroSystems
Microcomputer solutions for industrial control

 

[Joel Kolstad]

Someone know if is possible disable an USB port on Windows and use
Realistically, no. USB is only power, ground, and a sort-of differential
I/O line anyway. If you only need a single bit in and out, why not just use
RS-232? For that matter, take a look at FTDI's USB offerings -- they'll
sell you a single chip USB->RS-232 converter, so your product can easily
have both a RS-232 and USB interface.

 

[Denis Gleeson]

Hi Drazen

We are USB experts and have done a number of projects with it.
What you are suggesting doing is of course possible. But then isnt
everything.
Unfortunatly USB is a complex beast, particularly on the HOST side.
What you will find is that you will start to develop your own host
hardware and software despite your best efforts to create a simplified
interface.

Regrads

Denis

http://www.CentronSolutions.com
"From Concept to Production"

 

[Jan Panteltje]

The USB standards committee will not like you.

My PC fan, running from the USB took >600mA.
It only used the power lines.
I have been wondering WHO did it ;-) and HOW it got into the shops.
Finally the mobo switched the USB off.
I still have it, changed it a bit and it now runs on a DC adapter.
Also I can now control its speed with PWM and a PIC.
For the summenr time ;-)
Now that was something for the 'USB committee to think abot.

Next we will perhaps see battery chargers, desk lights, shavers, wht
not on USB power.
Someone REALLY has to stop that sort of stuff.
JP

 

[Spehro Pefhany]

My PC fan, running from the USB took >600mA.
It only used the power lines.
I have been wondering WHO did it ;-) and HOW it got into the shops.
Finally the mobo switched the USB off.
I still have it, changed it a bit and it now runs on a DC adapter.
Also I can now control its speed with PWM and a PIC.
For the summenr time ;-)
Now that was something for the 'USB committee to think abot.

Next we will perhaps see battery chargers, desk lights, shavers, wht
not on USB power.

I've seen all but the shaver already. USB battery chargers for your
laptop. Reading lights. Yup. That doesn't mean the shaver doesn't
exist, I've just not seen it. Why not a USB electric toothbrush.
There will probably end up being a defacto requirement to handle that
sort of crap, standards or not.

Someone REALLY has to stop that sort of stuff.
JP

Best regards,
Spehro Pefhany

 

[Ian Stirling]

Next we will perhaps see battery chargers, desk lights, shavers, wht
not on USB power.
Someone REALLY has to stop that sort of stuff.

I have a USB phone charger, bought for the princely sum of ninetynine pence.

It is a wonder of VLSI. (very low scale integration.)
The sole component is a resistor.

The nice thing about USB is it's a standard voltage, that's suitable for the
charging of a couple of NiMh or single Li-Ion cells found in most pocket-sized
devices.

There are AA/AAA battery chargers -
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=2989709574
and desk lights -
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=3463563019

It would have been nice if USB had some way to signal that a device
needed more power.
For example, a way to ask for 30V 0.5A, or to reverse the
direction of power flow, to allow charging of laptops through the
USB port, in a standard way that would work for any laptop.

For example, it'd be nice (at least I think so) if you could just plug
your laptop into a "high power" hub, and plug stuff like scanners/printers/
mice, all with just one cable, rather than needing a seperate power
cable.

 

[Jan Panteltje]

I have a USB phone charger, bought for the princely sum of ninetynine pence.

It is a wonder of VLSI. (very low scale integration.)
The sole component is a resistor.

The nice thing about USB is it's a standard voltage, that's suitable for the
charging of a couple of NiMh or single Li-Ion cells found in most pocket-sized
devices.

There are AA/AAA battery chargers -
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=2989709574
and desk lights -
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=3463563019

It would have been nice if USB had some way to signal that a device
needed more power.
For example, a way to ask for 30V 0.5A, or to reverse the

I see big problems there, suppose that request is honored.
Now you plug in some other device (mouse perhaps), it will fry.
Or it would have to have to regulator.
Also ground must make contact first.
And ;-) why stop at .5 A, PC supply can do many more amps at 5 V too,
and melt the cables.

I am very happy the mobos limit and switch of above 600mA

direction of power flow, to allow charging of laptops through the
USB port, in a standard way that would work for any laptop.

Lest keep those manufacturers of connectors going, separate
power connectors OK.

For example, it'd be nice (at least I think so) if you could just plug
your laptop into a "high power" hub, and plug stuff like scanners/printers/
mice, all with just one cable, rather than needing a seperate power
cable.

It is perhaps a bit of a dream, long ago I found out for me the 'all in one
power system' did not work.
Printers can take a **** lot of power, the voltage drops in those leads....
This resembles that thread on 12 V house supply a while ago after the power failure
in the US.
Too many practical hurdles.

I am for an optical cable, for chips interconnect, for peripherals, and separate
power supplies in each peripheral.
It always seems to make things really work well, complexity increases
I do agree that given the outrageous amount of adapters I now have,
solar power would get rid of a lot of stuff.
But we do not have enough sun here.
JP

 

[Ian Stirling]

I see big problems there, suppose that request is honored.
Now you plug in some other device (mouse perhaps), it will fry.

Not if it was originally specified.

Or it would have to have to regulator.

Regulators arn't very expensive.

Also ground must make contact first.
And ;-) why stop at .5 A, PC supply can do many more amps at 5 V too,
and melt the cables.

The connector issues and cable losses get nastier as you go above 0.5A
or so.

 

[Drazen]

Thank you for your soon reply, I would ask you other questions to best
understand.

We are USB experts and have done a number of projects with it.
What you are suggesting doing is of course possible.

Then you confirm that I can directly drive the USB motherboard chipset
bypassing tha USB protocol ?

Unfortunatly USB is a complex beast, particularly on the HOST side.

Why you tell me that USB is a complex beast if I want to completely bypass
the USB protocol ?
Maybe you intend that is difficult to bypass Windows and take a direct
control of the chipset ?

What you will find is that you will start to develop your own host
hardware and software despite your best efforts to create a simplified
interface.

I want to create a device that can be readed by my own controller and by a
PC but I search for a simplified way instead of developing USB protocol. I
don't want to use RS232 because is obsolete and it will quickly disappear
from PC. I wish to use USB port like a serial port using a personalized my
own protocol.
I know that this kind of device will not fit USB standards but is not a
problem. Any PC will use the dedicated USB port only for my device.
Do you have any other suggestion on how to solve this problem ? Also other
kind of suggetion are welcome !

Regards.

Drazen.

 

[Roger Hamlett]

Thank you for your soon reply, I would ask you other questions to best
understand.

Then you confirm that I can directly drive the USB motherboard chipset
bypassing tha USB protocol ?

Why you tell me that USB is a complex beast if I want to completely bypass
the USB protocol ?
Maybe you intend that is difficult to bypass Windows and take a direct
control of the chipset ?

I want to create a device that can be readed by my own controller and by a
PC but I search for a simplified way instead of developing USB protocol. I
don't want to use RS232 because is obsolete and it will quickly disappear
from PC. I wish to use USB port like a serial port using a personalized my
own protocol.
I know that this kind of device will not fit USB standards but is not a
problem. Any PC will use the dedicated USB port only for my device.
Do you have any other suggestion on how to solve this problem ? Also other
kind of suggetion are welcome !

Regards.

Drazen.

The problem you will have, is that to drive the chipset at the lowest level,
the addresses, instructions etc., needed, will change for different makes of
chipset. The only way I can think of being able to do this, and retain
compatibility on different boards, is to add a third party USB card, and
ensure that you are going to be able to source it for the lifetime of the
project. You can then deal with a single chipset, and write a driver to
operate this.
You are going to need to implement a fairly sophisticated protocol yourself
to do even a basic link, and you will have to cope with the situation of
other people attaching devices that are not the ones you expect.
I'd rate the development 'time', as possibly in the order of perhaps 6 'man
months', to code something to work for a single chipset. Seriously, you'd be
far better off, using an existing USB stack and driver (perhaps XP embedded
as an OS), and then just attaching your device using a USB-RS232 adapter
chipset (like the modules from FTDI). This could be operational in a few
days, and will give less problems, when in a few months time, a revision is
made to the USB chipset silicon, and the drivers need to be re-written...

Best Wishes

 

[Ian Stirling]

Thank you for your soon reply, I would ask you other questions to best
understand.

Then you confirm that I can directly drive the USB motherboard chipset
bypassing tha USB protocol ?

Why you tell me that USB is a complex beast if I want to completely bypass
the USB protocol ?
Maybe you intend that is difficult to bypass Windows and take a direct
control of the chipset ?

It is.
It may be impossible, if you want the device to be used by many.
A lot of the protocol is done in hardware.
There is relatively little software involvement.

PC but I search for a simplified way instead of developing USB protocol. I
don't want to use RS232 because is obsolete and it will quickly disappear
from PC. I wish to use USB port like a serial port using a personalized my
own protocol.
I know that this kind of device will not fit USB standards but is not a
problem. Any PC will use the dedicated USB port only for my device.
Do you have any other suggestion on how to solve this problem ? Also other
kind of suggetion are welcome !

http://www.ftdichip.com/
One chip that talks USB on one side, and either RS232, or an 8 bit
FIFO on the other.
Doesn't get much simpler.