I have a device that came with an AC power adapter where the connector is a mini USB plug. The device however doesn't seem to power itself from a computer's USB port (using a standard USB-mini USB cable) unless a specific driver is installed. The driver is only available for Windows. I would like to charge the device from USB plugs on different platforms.
My question is: why isn't power getting to the device without the driver? Is a driver always required for a USB port to start giving power? Or is it this device that's specifically made not to take a charge unless some software routine triggers it to do so?
I guess my question can be summarized as: Is power not present on the USB cable or is it present but the device ignoring it. If the answer is the former, I'll be trying to figure out how to write software that will enable the voltage to always be present.
Thanks
Why isn't power getting to the device without the driver?
USB ports are always powered when the computer is on and the USB control software hasn't detected current overdraw.
Is a driver always required for a USB port to start giving power?
No, the USB port is always required to start off providing power to the device, otherwise the device could never initiate a connection.
Or is it this device that's specifically made not to take a charge unless some software routine triggers it to do so?
This can be complex. To meet the USB spec a device cannot pull more than a few mA until it's registered with the computer.
However, nearly every computer allows the USB port to pull the full 500mA (and more) before it'll shut the power off.
The device you're charging is being nice by not pulling any significant power until the computer gives permission.
Writing software won't help, the device has to register with the USB bus, which will best be done with the driver.
However, the plug in charger doesn't do that. It likely has shorted the two data lines of the USB plug together, which signals the USB device that it's not connected to a computer and can pull the full 500mA without waiting.
Take a USB extension cable, cut off the jacket, and short the data lines (green and yellow, sometimes) together on the end going to the USB device, and leave them cut without touching anything on the end going to the PC, and leave the read and black power wires connected through.
It might work. If not, take the wall charger apart and find out what it's doing with each of the four USB wires, and see if you can duplicate that.
This might be helpful if you are targeting a linux system.
This seems to be platform-specific. In Linux, USB ports are always energized, while on Windows they don't. Thumbdrives with LEDs turn off when unmounted in windows, but in Linux they stay lit. My cellphone's manual says that it can't be charged by a PC, but I regularly do on my linux machine, I guess that's because they don't have a driver and windows won't power up without one.
Have you tried plugging it into a 'dumb' USB port - like the one on a car charger? Those ports are pure power and don't create a USB network. I think.
Unless you have the hardware specs from the manufacturer, I think you are out of luck. You could try reverse engineering the driver to see what it does, but I'd expect it would be cheaper and easier just to buy one with cross platform drivers or charges without the driver.
Related
I have a USB lamp,which just switches on when plugged into a USB port. I connected it to my computer and ran lsusb, but could not find the device. How does the OS handle these devices? Are the USB power pins always powered with 5V, or does it get powered when the OS detects a device? If the OS detects a device and then supplies power to the USB slot, how do I locate the drivers associated with the device?
The device is something similar to the device listed here:
https://www.amazon.in/Codered-Portable-Flexible-Light-Colors/dp/B078N9DQ8B
From the image and description below, the product in question looks like a "dumb" device to me. By dumb i mean it only uses the +5V and GND lines from the USB connector. The D+/D- used to communicate are not connected and therefore no drivers are required/applicable. Given USB is a fairly complex and comprehensive protocol, you could probably pick up a copy of USB Complete: the first few chapters should get you started in the right direction.
I have also found this helpful.
BTW, external links (esp amazon products) tend to die, so upload and include a picture (when you have the reputation points) otherwise the context of the question can be lost.
I work with an embedded device that has a USB host port. I would like to connect an iPhone to it and communicate via USB. I have done development on this and ported the functionality to connect to usbmux on the iPhone and have successful communication, however there is another problem.
All development was done with the iPhone connected to a powered USB hub that was connected to my device, as soon as I connected it directly, after enumeration it starts to drain the battery of my embedded device and causes a tension (voltage) drop that causes my device to turn off.
I know that after enumeration usb devices can draw up to 500 mA from the usb port, but I was wondering if there was a way to limit that to 100 mA (while still having the iPhone registered).
I found various questions regarding controlling voltage on the data pins or vcc from the usb port and I understand that's not possible, I'm looking for a software solution (although hardware solutions are welcome).
tl;dr: Is there a way to supply the iPhone with less than 500 mA after enumeration? Could I do this in software? Or do I need a hardware solution? I don't want to turn the port on/off, just limit the power draw of the iPhone.
NOTE: I am using Windows CE 6.0, if it is something that can only be done by modifying the drivers, or having direct access, there is no problem.
P.S. also, if there is a way to do this in *nix (or some other open source OS) that I could look at the source code and port it to Windows CE please let me know.
When a device shares its available configurations (see USB chapter 9), it specifies how much power it requires for each configuration. The host should look at all the available configurations and choose which one it wants.
In practice, however, these things don't work so smoothly.
The last time I looked at this, Windows always chose the first configuration. MacOS always chose the lowest power configuration (or highest, I can't remember). I never looked at WinCE or Linux.
If you're writing/modifying the driver, you can set your own rules for which configuration to choose, including looking for one that's 'self powered'. The iPhone, however, might only have one descriptor that always requests 500mA, bus powered. If so, then you're pretty much screwed since there's no way to let the iPhone know it's not OK to draw power.
That being said, I believe all the iPhone accessories are actually USB host (as opposed to USB device), and given that they don't always supply power, the iPhone must be capable of enumerating self powered.
I like the answer by Russ Schultz but I want to add another one:
No.
The descriptor of the peripheral device, iPhone in this case contains bMaxPower. If you enumerate this device, you also accept the power demand. It is not possible to only supply less, lets say 300 mA, if you already enumerated the device with the 500 mA desriptor. If this is what you wanted.
If the device provides multiple configurations, you are as mentioned by Russ free to write a driver which selects the configuration with less power. Hopefully, the device will then only consume the granted power.
Many peripheral devices just don't care. Most devices only provide one configuration with 500 mA. And there are a lot of devices which just consume more than they say ...
I'm looking to control a mains powered light from a simple relay switch connected via USB to the computer.
The relay switch isn't even a USB device, it's just a simple switch that requires the USB voltage to turn it on. When the voltage drops below a threshold, the switch will turn the light off.
My problem is that I can't control the power output of a USB port. I'm happy to do it using any language on Windows or Linux (but preferably Java because I'm used to it).
Unfortunately, in most cases you cannot control the power supply to the USB port. The power supply is usually hardwired through, and not switchable in software. You can send a reset to a USB device, but that won't work in your case.
There are a number of projects on instructables that do similar to what you describe, but unfortunately they seem to either be quite complicated or require expensive parts.
EDIT: There is actually a product currently in the news which would do want you want, but it doesn't appear to be shipping yet: http://www.pwrusb.com/
EDIT (again): Apparently you can do this with some usb hubs. This post sugggests the Linksys USB2HUB4 is one that works.
EDIT (and again): Apparently there are a number of similar questions, but there don't seem to be any more useful answers:
https://stackoverflow.com/questions/405269/custom-usb-device-that-disables-power-to-usb-devices-plugged-into-it
Power off an USB device in software on Windows
Is there software or code to alter USB power output
Can I write a program that swiches USB on/off
Most of the USB to Serial or USB to RS232 $10 converters support hardware handshaking. Use one of those as a single channel digital io.
Connect your transistor that will drive the relay to DTR on the converter board and command DTR ON/OFF with the converters driver.
A 2N7002 is a good transistor to use (FET actually) since it will work from 3V and doesnt need any resistors anywhere.
Here is a complete solution.
It uses an Arduino board, with a USB connection, (and Uno for example) to control the relay and combines this with pfod (Protocol for Operation Discovery) www.pfod.com.au which will let you control the board/relay from either the Arduino IDE SerialMonitor, or a terminal window (TeraTerm) or a Java program. The message protocol encloses commands in { }, think simplified html for micros, and provides numerous screens, menus, sliders, text and numeric inputs, etc. A detailed protocol spec is available
See Garage Door Remote for a detailed example, with full Arduino code and an example of controlling the relay from TeraTerm as well as the Arduino IDE SerialMonitor.
There is also an Android app, pfodApp, which will do general purpose control via bluetooth, or wifi/internet with 128 bit security. The pfodApp does all the Android stuff, you only need to code some simple strings in your Arduino code to get any menu system you want. See www.pfod.com.au for numerous examples.
You need a USB-GPIO microcontroller:
Adafruit FT232H (about $15)
Arduino Nano ATmega328 (about $7)
See this answer
I would suggest placing a separate Raspberry Pi unit with a wake-on-lan feature activated so you can ping it off and on.
You could do it by combining these two products from Pololu, for about $25:
Micro Maestro (assembled)
Basic SPDT Relay Carrier with 5VDC Relay (Assembled)
The Maestro is mainly a servo controller but you can set any of its channels to be simple digital outputs instead. The output can be controlled from the Maestro Control Center software or you can write your own software. A digital output from a Maestro is suitable to turn on the relay on the relay carrier. The relay could be powered from USB through the Maestro; I think it draws about 100 mA of current so that probably will not be a problem for most USB ports, though it would not be USB-compliant because the total current drawn by the Maestro and the relay would be over 100 mA. You could supply your own power source for the relay if you are worried about that.
I want to be able to turn my PC on and off using an IR-remote sensor that is connected via USB to the PC. The sensor is a custom PCB implemented with an AVR microprocessor and V-USB software USB-implementation.
Now, turning off the PC is no problem with software, but is there any way to turn ON the PC using USB?
(Please note, I'm not talking about booting from USB-stick or USB-power supply ...)
There seem to be two problems:
keeping the USB powered on while the PC is off. It seems that most mainboard have a jumper for this functionality.
bringing the PC back to life. There seems to be no standard functionality for this. The solution is to "press" the PCs power button through the AVR on the USB board. I know, this means extra cable from the USB to the PC, but it seems to be the easiest solution.
Another workaround could be to send the power-on signal to the PC over ethernet. But I guess this will be more complicated than the power button solution and it involves extra cables too.
This Microsoft knowledgebase article describes how to enable "wake on USB" for a USB mouse. I just checked, and my keyboard device entry (on Windows Vista) has the same choice, already checked.
So, if your AVR is emulating a USB keyboard or mouse, it should be possible to wake the computer by sending the proper data.
there must be a way to do this with USB, since some PCs can be switched on with the keyboard. I think this will be some looking whether your mainboard/BIOS support it (it may be you need to turn it on in BIOS, this will probably also ensure your device gets power from USB although the PC is switched off), and whether that V-USB (unknown to me) can send the "wakeup"-signal.
good luck !
How "off" does the PC need to be? Is waking from sleep/suspend enough? The USB standard describes "remote wake-up".
Aside from enabling remote-wakeup, like unwind mentions, software on the PC is not involved in making this work.
I have a piece of hardware that sends USB data over ethernet (only the data stored in the package will be send). On a remote PC the data is recieved via ethernet. How can I send this data to the USB driver so it translates the data into commands applications can use?
You're better off getting hardware that does the reciprocal, sends the IP-based USB information to the USB subsystem, rather than try and hack the software driver itself. I can't imagine your hardware vendor doesn't have a device that does this.
You need a server listening on whatever port/socket that you are trying to connect to. Twisted Matrix makes decent Python libraries for network communications.
I think this is going to be troublesome.
USB is generally set up to associate a driver with a connected device, based on the device's various ID numbers, as discovered during bus traversal.
Your data comes in over Ethernet, so the platform's USB driver stack won't know anything about the device in question. This means you somehow need to directly talk to the proper driver, and also get it prepared to handle events from a (from its point of view) non-connected device.
I can think of several reasons why even a well-designed USB stack won't handle this happily.
On Linux, you might be able to "cheat" by interpreting the data yourself and sending it on, using the same API:s the actual driver would have used. That won't work for any USB device of course, it requires you know what the device is.
It's doable on windows as well, but you need a lot of kernel/usb knowledge to make it work i don't think i will be wrong by estimating this task as few man years (you can reduce this estimation dramatically if you have a limited selection of devices/types of device to support.
You will need to develop a bus driver that will simulate the host controller driver to the native usb host, unfortunately this interface is not public and we did not managed to get MS cooperation on that.
There is additional option to work on hub level, instead on controller level, this interface is available, but i did not managed to find my notes on that.
You can download the evaluation version and investigate the driver stack it might give you a clue where to start.