I had a look at this and this but no one sounded particularly sure of their ideas and I'm kind of after a different thing anyway. I want to hook my usb power cables (red and black) up to my phone so I don't have to use a battery (the battery is dead anyway and this is just an experiment). The problem is that USB standards ensure that a minimum of 4.35V is supplied, when I only want 3.7V. Does anyone know for sure that you can or cannot regulate power output programmatically? Some other queries I have are: What kind of power does the sleep mode provide? And what would I need to code something in to play with this, C++?
No, you won't find a computer that allows you to set this voltage in software. It would break the USB specification.
You can get 150mA by default, and 500mA if your USB device negotiates it with the computer (requiring a little bit of logic in the device). Multiply by 5V to get the provided power.
A bit more info on the answer from Pascal:
The normal operation (Non-Configured mode) is 100mA
In theory, the operating system should check the MaxPower value of the device's configuration descriptor to decide if to allow it to draw more than 100mA.
In practice, PCs do not do it (and have no way to control it). So you can try taking 500mA.
(Of course connecting a bus powered hub and linking more then one 500mA device, should, not work.)
If the device is not actively used, the OS may (and should) suspend it. When suspended the power is limited to 1-0.5mA (Again, in theory, since it can not be controlled by software).
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 am a physicist, and I had a revelation a few weeks ago about how I might be able to use my personal computer to get much finer control over laboratory experiments than is typically the case. Before I ran off to try this out though, I wanted to check the feasibility with people who have more expertise than myself in such matters.
The idea is to use the i/o ports---VGA, ethernet, speaker jacks, etc.---on the computer to talk directly to the sensors and actuators in the experimental setup. E.g. cut open one side of an ethernet cable (with the other end attached to the computer) and send each line to a different device. I knew a postdoc who did something very similar using a BeagleBone. He wrote some assembly code that let him sync everything with the internal clock and used the GPIO pins to effectively give him a hybrid signal generator/scope that was completely programmable. It seems like the same thing should be possible with a laptop, and this would have the additional benefit that you can do data analysis from the same device.
The main potential difficulty that I foresee is that the hardware on a BeagleBone is designed with this sort of i/o in mind, whereas I expect the hardware on a laptop will probably be harder to control directly. I know for example (from some preliminary investigation, http://ask.metafilter.com/125812/Simple-USB-control-how-to-blink-an-LED-via-code) that USB ports will be difficult to access this way, and VGA is (according to VGA 15 pin port data read and write using Matlab) impossible. I haven't found anything about using other ports like ethernet or speaker jacks, though.
So the main question is: will this idea be feasible (without investing many months for each new variation of the hardware), and if so what type of i/o (ethernet, speaker jacks, etc.) is likely to be the best bet?
Auxiliary questions are:
Where can I find material to learn how I might go about executing this plan? I'm not even sure what keywords to plug in on Google.
Will the ease with which I can do this depend strongly on operating system or hardware brand?
The only cable I can think of for a pc that can get close to this would be a parallel printer cable which is pretty much gone away. It's a 25 wire cable that data is spread across so that it can send more data at the same time. I'm just not sure if you can target a specific line or if it's more of a left to right fill as data is sent.
To use one on a laptop today would definitely be difficult. You won't find any laptops with parallel ports. There are usb to parallel cables and serial to parallel cables but I would guess that the only control you would have it to the usb or serial interface and not the parallel.
As for Ethernet, you have 4 twisted pair with only 2 pair in use and 2 pair that are extra.
There's some hardware that available called Zwave that you might want to look into. Zwave will allow you to build a network of devices that communicate in a mesh. I'm not sure what kind of response time you need.
I actually just thought of something that might be a good solution. Check out security equipment. There's a lot of equipment available for pc's that monitor doors, windows, sensors, etc. That industry might what your looking for.
I think the easiest way would be to use the USB port as a Human Interface Device (HID) and using a custom built PIC program and a PIC that includes the USB functionality to encode the data to be sent to the computer and in that way be able to program it independently from the OS due to the fact that all mayor OS have the HID USB functionality.
Anyways if you used your MIC/VGA/HDMI whatever other port you still need a device to encode the data or transmit it, and another program inside the computer to decode that data being sent.
And remember that different hardware has different software (drivers) that might decode the raw data in other odd ways rendering your IO hardware dependent.
Hope this helps, but thats why the USB was invented in the first place to make it hardware and os independent.
I would like to have Arduino operating in a CAN network. Does the software that provides OSI model network layer exist for Arduino? I would imagine detecting the HI/LOW levels with GPIO/ADC and sending the signal to the network with DAC. It would be nice to have that without any extra hardware attached. I don't mind to have a terminating resistor required by the CAN network though.
By Arduino I mean any of them. My intention is to keep the development environmen.
If such a software does not exist, is there any technical obstacle for that, like limited flash size (again, I don't mean particular board with certain Atmega chip).
You can write a bit banging CAN driver, but it has many limitations.
First it's the timeing, it's hard to achieve the bit timing and also the arbitration.
You will be able to get 10kb or perhaps even 50kb but that consumes a huge amount of your cpu time.
And the code itself is a pain.
You have to calculate the CRC on the fly (easy) but to implement the collision detection and all the timing parameters is not easy.
Once, I done this for a company, but it was a realy bad idea.
Better buy a chip for 1 Euro and be happy.
There are several CAN Bus Shield boards available (e.g: this, and this), and that would be a far better solution. It is not just a matter of the controller chip, the bus interface, line drivers, and power all need to be considered. If you have the resources and skills you can of course create your own board or bread-board for less.
Even if you bit-bang it via GPIO you would need some hardware mods I believe to handle bus contention detection, and it would be very slow and may not interoperate well with "real" CAN controllers on the bus.
If your aim is to communicate between devices of your own design rather than off-the shelf CAN devices, then you don't need CAN for that, and something proprietary will suffice, and a UART will perform faster that a bit-banged CAN implementation.
I don't think, that such software exists. CAN bus is more complex, than for example I2C. Basically you would have to implement functionality of both CAN controller and CAN transceiver. See this thread for more details (in German).
Alternatively you could use one of the CAN shields. Another option were to use BeagleBone with suitable CAN cape.
Also take a look at AVR-CAN.
Is it possible to program a wireless adapter attached to a computer?
I need to modify how they work, not just using them to perform a task such as scanning or connecting.
I have already tried the Native Wifi API, but that library is too high level. I cannot modify how exactly the wireless adapter works.
Any solution in any programming language in any operating system is very welcomed. (Sounds so desperate lol)
You need an open-source operating system then. Hardware varies in how programmable it is, but for example, Atheros wireless cards do not have an on-board processor, and therefore they do the absolute minimum of the 802.11 protocol in hardware, leaving everything else to the device driver. More info in these places: http://linuxwireless.org/ http://git.kernel.org/?p=linux/kernel/git/linville/wireless-testing.git;a=summary;
If you really need to go further that what commodity hardware can do, look in to GNU Radio and the USRP/USRP2: http://gnuradio.org/redmine/wiki/gnuradio
And yes, you do have to be careful about the legal implications of this stuff, but then if you don't turn off the regulatory framework, there is software to help with that.
Generally speaking, the manufacturer will attempt to prevent you from doing this. Since what you're working with is really a radio transceiver, its operation is regulated. In the US, for example, such things fall under the purview of the FCC. Depending on the country, changing how it operates (and then operating it) is likely to be illegal.
If you have an atheros chipset on your WLAN card then load up linux and install ath5k/ath9k or madwifi and you can do some interesting things with the driver.
In the world of embedded software (firmware) it is fairly common to observe the order of events, take timings and optimise a program by getting it to waggle PIO lines and capturing their behavior on an oscilloscope.
In days gone by it was possible to toggle pins on the serial and parallel ports to achieve much the same thing on PC-based software. This made it possible to capture host PC-based software events and firmware events on the same trace and examine host software/firmware interactions.
Now, my new laptop ... no serial or parallel ports! This is increasingly the case.
So, does anyone have any suggestions as to go about emitting accurate timing signals off a "modern" PC? It strikes me that we don't have any immediately programmable, lag-free output pins left.
The solution needs to run off a laptop, so using add-on cards that only plug into desktops are not permitted.
Laptop with a docking station and old-skool parallel port. An alternate is to use a "smart" box connected via USB that handles the timing for you and simply reports the results over USB.
You may want to look into some of the USB logic analyzers like the Saleae Logic kit.
You can get USB dongles that create serial and parallel ports. Make sure you do your homework though, as you want to be sure that you can get all the Pins and all their data, some of the cheaper units don't do everything you need.
I've got a PCMCIA parallel port from Quatech - model SPP-100. It is a "real" parallel port - not a USB-Parallel port one. It is "real" enough to allow me to use a parallel port dongle with Windows 7 x64 on my laptop which doesn't have a parallel port.
How about using the audio line-out port? That should at least have consistent latency since audio applications care about that. That's the only modern computer output I can think of that isn't packet-based or dedicated to other purposes. It only has two channels (though external USB audio devices could expand that, and hopefully also have consistent latency through whatever the protocol does), and there might be a DC filter, but you could at least produce reliably timed pulses.
USB logic analyzers exist, some are even chip. But keep in minds #xtofl's comment about timing.
sump.org
The Bus Pirate