I am looking into ways to stream a usb camera over long distances. The plan is to plug the USB into a raspberry pi2, then send it over wifi via TCP. Is this a viable plan?
I have found a few approaches like this:
https://www.virtualhere.com/
But They seem to be for printers and other 'static' devices. Will a streaming data connection work with this type of approach?
Thanks.
Yes, a USB camera uses the "isochronous" transfer mode of the USB protocol.
VirtualHere and most other usb/ip software support this mode.
The main issue is network latency. The lower the webcam resolution, the less latency will be a problem. Also, the pi2 has a fast CPU however the USB bus is shared with the Ethernet so by definition throughput is cut in half, perhaps looking at a embedded board that doesn't share the USB bus like a beaglebone or odroid-c1 or other board would provide better performance for the same price.
(I am the author of VirtualHere)
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 am working on a project that uses the Arduino Due (microcontroller ATSAM3X8E). My goal is to be able to track the values of some of the key variables I am using in my firmware in real time. The fact is that I need to plot the change in the values of the variables over time.
In order to do this, I have decided to send the data to my PC through the native USB port. The real time constraint I am having is that I need to send the values of 20 variables (each of them 8 bytes long) within 0.1 ms. There is a native USB port available on the Arduino Due, which is connected to the USB peripheral of the chip. I have tried using UART over USB by setting up the Due in USB device mode. I can only get up to speeds of 115200 baud using Serial (UART) communication (any higher speeds don't allow the Due or my host PC to send the data correctly).
So, I did some home work and found that USB based devices have different classifications based on what they do. I want to know if there is a high speed protocol with a speed of at least 2 M bits/sec I can use on top of USB to data across to my PC from the Due, and, if there is an equivalent driver I can use on my Windows PC to successfully capture that high speed data - any recommendations would be greatly helpful.
Thanks in advance!
Subramanian
The Arduino Due's native USB port is capable of high-speed USB (480 Mbps), and by default it will appear to the computer a USB virtual COM port. This is a virtual serial port, so you can send data as fast as the USB drivers will allow, and you are not limited by the virtual "baud rate" of the COM port, which is an irrelevant setting. I think the virtual COM port will be fast enough for you and you should try it before doing something more complicated.
To use this port, use the SerialUSB in your Arduino program. The object has the same interface as Serial. You should already have a drivers for it if you installed the Arduino IDE or you are running Windows 10.
Please note that USB virtual COM ports usually use USB bulk endpoints, which don't guarantee any paritcular latency or throughput. If your computer is busy talking to other devices on the bus, you might get less throughput then you were hoping for, but you have a lot of margin of error here so I don't think it will be a problem in practice. If you want to be safe, just make sure that you can buffer up a few milliseconds of data on the device side so you aren't losing any data. You might have to look at the internals of the Arduino core code to see how big its buffers are.
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 would like to implement usb communication at a speed of 30Mbit/sec. My hardware support "high speed usb" so the hardware platform will not limit me.
Can I implement this speed using USB CDC class, or Mass storage class, or are these usb classes speed limited?
In USB protocol who determines the bit rate, is it the device?
The USB CDC and mass storage classes do not have any kind of artificial speed limiting, so you can probably get a throughput of 30 Mbps on a high-speed USB connection (which uses 480 Mbps per second for timing bits on the wire). The throughput you get will be determined by how much bus bandwidth is being used by other devices and how efficiently your device-side firmware, host-side driver, and host-side software operate.
The bit rate is mostly determined by the device. The device basically signals to the host what USB speeds it supports, and the host picks one. The full story is a little bit more complicated, and there are a lot more details about how that works in the USB specification.
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.