- USB power to external device
- Posted by martin griffith on February 15th, 2007
Not sure if this is the right place , but:
I need to power some analogue stuff from a USB port, and AFAIU the USB
on the PC/MAC will limit the current available to 100mA on connect. I
think I will need about 200mA, so how do I "simply" inform the source
to let me have it?
This is mainly to power a transformer isolated smps +-12v for opamps,
a (nonPIC) micro could be powered from the USB source.
Clutching at straws again.......
martin
- Posted by Andy Peters on February 15th, 2007
On Feb 15, 2:38 pm, martin griffith <mart_in_medina@ya___.es> wrote:
You "inform" the bus by properly enumerating your gizmo as a valid USB
device.
-a
- Posted by martin griffith on February 15th, 2007
On 15 Feb 2007 14:20:40 -0800, in comp.arch.embedded "Andy Peters"
<google@latke.net> wrote:
do the enumeration?
martin
- Posted by Steve Calfee on February 16th, 2007
On Fri, 16 Feb 2007 00:51:00 +0100, martin griffith
<mart_in_medina@ya___.es> wrote:
"power required" field in milliamps. Any powered port (including the
root hub in the pc) must be able to provide 500 ma. An unpowered hub
port can only provide 100 ma. So you should be able to do what you
want, but you will restrict the usb topology.
Regards, Steve
- Posted by galapogos on February 16th, 2007
On Feb 16, 9:46 am, nospamcal...@yahoo.com (Steve Calfee) wrote:
Here's a question. How about those USB enclosures or other USB devices
that use a USB Y-cable? Presumably 1 device can only enumerate once,
so it'll get 500mA on 1 cable, but the other cable will only get
100mA? Or also 500mA? I believe it's 500mA since most drives will need
more that much(or even more) to work? How does it work then?
- Posted by Andy Peters on February 16th, 2007
On Feb 15, 4:51 pm, martin griffith <mart_in_medina@ya___.es> wrote:
There are various micros from Cypress, Microchip, Silicon Labs, TI,
Atmel, etc, which have USB device interfaces. Choose one. Choose a
device class with which your device will conform (HID is probably
simplest), and be sure to include the desired current draw in the
device/configuration descriptor. Once the device enumerates, which
means it's recognized by the operating system and the device driver is
loaded, then you'll be able to use the 500 mA available to the port.
The point here is that you can't "steal" power from the bus ... you
need to have a proper device connected to the bus before you are able
to use all of the power.
-a
- Posted by Andy Peters on February 16th, 2007
On Feb 16, 12:30 am, "galapogos" <gois...@gmail.com> wrote:
There's no such thing as a USB Y cable.
And before you jump my shit: I'm sure somebody's out there making
them, but I wouldn't plug one into my computer or my device and expect
anything to work (or not explode).
They're kinda like those USB turnaround thingies you see ... utterly
pointless.
-a
- Posted by martin griffith on February 16th, 2007
On 16 Feb 2007 09:19:44 -0800, in comp.arch.embedded "Andy Peters"
<google@latke.net> wrote:
crossed my mind.
martin
- Posted by martin griffith on February 16th, 2007
On 16 Feb 2007 09:19:44 -0800, in comp.arch.embedded "Andy Peters"
<google@latke.net> wrote:
http://www.ti.com/litv/pdf/slyt118
martin
- Posted by Don McKenzie on February 16th, 2007
martin griffith wrote:
Have a look at:
http://www.dontronics-shop.com/produ...roductid=16456
100ma
and
http://www.dontronics-shop.com/produ...roductid=16141
500ma, 5V, 3.3V, and USB RX and TX at TTL levels if you need them.
May be an overkill for what you want, may not be, but at least an
alternative.
Don...
--
Don McKenzie
E-Mail Contact Page: http://www.dontronics.com/e-mail.html
Crystal clear, super bright OLED LCD (128x128) for your microcontroller.
Simple serial RX/TX interface. Many memory sizes.
http://www.dontronics-shop.com/produ...roductid=16460
No More Damn Spam: http://www.wizard-of-oz.com
- Posted by martin griffith on February 16th, 2007
On Sat, 17 Feb 2007 08:15:28 +1100, in comp.arch.embedded Don McKenzie
<look@mysig.com> wrote:
had a couple of vino's, so I read it in the am
anyway, done some diging and found
http://www.obdev.at/products/avrusb/index.html
might be something in it for you?
martin
- Posted by Don McKenzie on February 17th, 2007
martin griffith wrote:
Thanks for the good feed back Martin.
I'll have a good read of it shortly also.
I do have a couple of alternatives here as well:
15-Feb-2007
The FTDI VDIP1 module is an MCU to USB host controller development
module for the VNC1L device. VDIP1 is supplied on a PCB designed to fit
a 24-pin DIP socket and provides access to all UART, SPI and FIFO
interface pins of the VNC1L device.
http://www.dontronics-shop.com/produ...roductid=16621
15-Feb-2007
The FTDI VNC1L USB Host Controller ICs not only handle the USB Host
Interface, and data transfer functions but owing to the inbuilt 8/32-bit
MCU and embedded Flash memory, VNC1L encapsulates the USB device classes
as well. When interfacing to mass storage devices such as USB Flash
drives, VNC1L also transparently handles the FAT file structure
communicating via UART, SPI or parallel FIFO interfaces via a simple to
implement command set.
http://www.dontronics-shop.com/produ...roductid=16620
Don...
--
Don McKenzie
E-Mail Contact Page: http://www.dontronics.com/e-mail.html
Crystal clear, super bright OLED LCD (128x128) for your microcontroller.
Simple serial RX/TX interface. Many memory sizes.
http://www.dontronics-shop.com/produ...roductid=16460
No More Damn Spam: http://www.wizard-of-oz.com
