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.
Related
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 trying to configure/write VHDL code that would let me output or input data from the USB port on a Basys3 FPGA board. Problem is I have yet to found any threads or questions that talk about this topic.
The nearest thing to an answer I've found is this:
Provide input data to FPGA using USB
and it does not contain what I'm looking for.
Any clues anyone¿?
The Basys3 board has a usb-uart bridge chip as described in the reference manual. This will appear to a PC (or any device with a usb host and the appropriate usb-serial drivers) as a virtual com port. Sending data to and from a PC com port is quite easy.
You will need a uart implementation on the FPGA. There are lots of example designs on the web. One way is to implement a soft core microblaze processor with a uart peripheral in the FPGA. This example looks like it includes foundation for the functionality you desire.
The simplest implementation from the PC side is using a terminal program such as putty, Tera Term or realterm. Most languages include com(serial) port libraries or bindings. This type of interface tops out at a raw bandwidth of around 3-12Mbits per second depending on the drivers and implementation.
Read the manual for the Basys 3 board. It will explain how you can interface with USB devices plugged into the USB port. Be warned, however, that your options are pretty limited.
Short version: if you plug in a USB mouse or keyboard, they will be exposed to your design as an emulated PS/2 device. USB storage devices can be used to configure the FPGA. Other devices are not supported.
I am working on Xilinx Spartan 3E platform, using this development board:
http://www.xilinx.com/products/boards-and-kits/HW-SPAR3E-SK-US-G.htm
My program operates on certain data and then provides output. I wish to transfer the input signals externally. The input data is a stream of 8-bit signals.
So, how do I send the input signals from my laptop to the FPGA via USB? Does Xilinx support this or is there standard software to do this?
Thanks.
It sounds like you are describing a uart more than a native USB interface. You can get a USB to logic level serial adapter that will let you easily transfer data to and from a Pc at up to 921.6k baud. A uart/serial port is easy to implement in the Fpga and PCs are easy to use with serial ports.
Here is the cable:
http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm
If you have a development card it is very possible this type of interface is present.
On the software side you can use your programming language of choice as if it was interfacing with a seal port or use a terminal program like hyper terminal or Download teraterm http://ttssh2.sourceforge.jp/
Updated response:
100Hz is not a hard interface to make. At that rate you should use the serial interface if at all possible. The board you referenced has 2 full RS-232 connections. At that point you only need a way to connect that to your computer. If you have a PC with RS-232 connectors you only need a cable if you have a newer computer without you need a RS-232 to USB translator cable (like this one: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=768-1014-ND or google rs232 usb). This will give you a virtual com port on the pc to interface with the previously mentioned terminal programs or your custom software.
Update 2:
on the resource tab of the development board page you linked to there are several UART based fpga designs that you should be able to use as a starting point.
i.e. the "PicoBlaze Processor SPI Flash Programmer".
That board doesn't provide easy access to the USB interface from the FPGA as far as I can tell. It's just for configuration and debug.
Some of the newer boards and tools do allow something called hardware-in-the-loop testing where the simulator can upload data to the FPGA, wait it to calculate the results and then pull the data back. This is relatively common when using Xilinx's System Generator product as the simulations can be really long.
But I think with that board you'd be better off using the on board RS232 port to get data to and from the board. You will have to build the infrastructure to do it yourself though.
This may also give you some ideas:
http://www.1pin-interface.com/
I have a Korg NanoKey which I'd like to use to control a simple synthesizer I've designed on the Arduino platform. (I have an Arduino Uno.) Basically, I don't care about MIDI, I just want to read what note the keyboard has pressed down, but if MIDI is the only way I can do that, then it's okay with me. So my big question is, how do I do this? I haven't been able to find anyone else on the Internet who has already done this.
But more specifically, I see two challenges: First, I'd like to plug my NanoKey directly into the Arduino's USB port, but then I'm wondering if the Arduino would provide the necessary power to the NanoKey. Second, I'm not sure what protocol I would be reading. Can I just read MIDI signals as described in this tutorial?
I don't want to curb your enthusiasm but what you're attempting might be a bit hard basket. A USB system consists of a host controller and one or more peripheral devices. It's the host that controls traffic flow to the devices which means that devices can't transmit data on the bus without an explicit request from the host controller.
I'm not familiar with either the nanoKey or the Arduino platform but I'd be fairly confident that the nanoKey is a USB "device", normally connected to a computer which would act as the host. So what you would need for this system to work is for the Arduino to act as the host when communicating with the nanoKey. The Arduino schematic shows that the Arduino Uno uses an ATmega8U2 for USB coms. Unfortunately the ATmega8U2 is a USB device, so you've got two peripheral devices but no host controller to facilitate the transfer of data between them. You'd be better off using a development board for a micro that provides either USB Host or USB On-the-Go.
I opened up a Korg Nano controller yesterday and was surprised to discover that there's an AVR mega32 inside. It would be a significant undertaking, but with a bit of work you could probably work out the schematic and reprogram it yourself using their programming header breakout. You might not end up with much more functionality than you've got this other way, but it would be very educational.
I agree with the Jono - you are biting off a lot - it might even end up easiest to hook the keys up to the Arduino directly - tearing out the electronics and figuring out a way to multiplex the keys into a single channel without losing polyphony (resistor 'ladder' maybe). I any case, good luck. Amusingly, you'd making an analog keyboard to plug into a digital synthesizer.
Quick and Dirty Arduino MIDI Over USB demonstrates how to send/receive MIDI out over USB, but unfortunately, this probably isn't any help for what you are trying to do, since he's found a way to send and receive MIDI signals from a USB host, not act as a USB host himself - the opposite of your problem. However, I thought perhaps it would be of use, if you ever wanted to control your device from a computer.
As mentioned in the other posts, you would need to use a separate chip to provide the USB Host interface. Here's a great guide to using the USB Host shield by Circuits#Home to interface with an Akai LPK25 (USB Midi Keyboard).
http://blog.makezine.com/2010/11/30/usbhacking/
The Arduino sketch is provided, so you should be able to try it out, however debugging the USB Host connection could get tricky real fast if it doesn't work out of the box.
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.