I would like to connect 2 usb webcams to a RaspberryPI and be able to get at least 1920 x 1080 frames at 10 fps using OpenCV. Has anyone done this and knows if this is possible? I am worried that the PI has only 1 usb bus?? (usb2) and might get a usb bandwidth problem.
Currently I am using an Odroid and it has a usb2 and usb3 bus so I can connect 1 camera to each without any problemo..
What i have found in the past with this is no matter what you select using OpenCV for bandwidth options the cameras try to take up as much bandwidth as they want.
This has led to multiple cameras on a single USB port being a no-no.
That being said, this will depend on your camera and is very likely worth testing. I regularly use HD-3000 Microsoft cameras and they do not like working on the same port, even on my beefy i7 laptop. This is because the limitation is in the USB Host Bandwidth and not processing power etc.
I have had a similar development process to you inthe past though, and selected an Odroid XU4 because it had the multiple USB hosts for the cameras. It also means you have a metric tonne more processing power available and more importantly can buy and use the on-board chip if you want to create a custom electronics design.
Related
I'm deciding between the MiniPCIe and USB accelerators for a home Linux CCTV project. The host has both USB3 and a MiniPCIe socket. The host's physical environment will range from an ambient 20C up to a potential 35C (during the summer).
I'm struggling to determine the pros and cons for each. I have gotten this far, although many are guesses:
USB:
Supports Windows and MacOS as well as Linux
Appears to have greater mindshare/use/community support on the Internet
External so can be placed to optimise heat dissipation
Heatsink
Two manual performance modes, highest requires ambient temp of max 25C
Can use up to 4.5W (900mA # 5V)
Mini PCie:
Cheaper (25%)
Lower power consumption (1.4W for 416 fps)
Automatic thermal throttling via driver
Relies on host system for active cooling
Will maintain max operation at 85C
There's probably many I've missed. In particular I can't determine if there's any limitations on throughput/capacity using USB vs PCIe. If there is no difference, then I suspect the USB form factor is the better option, if only for the mindshare, although the power usage/heat generated may be a concern.
To whittle this down to an actual question: in what cases would the Mini PCIe interace be a preferred option to the USB one?
If you are looking for a plug&play solution, then I definitely suggest the USB Accelerator. Overall, as long as you have the system requirements then it'll always works (maybe with some modifications to the standard linux configs like adding your user to the plugdev group, ...). Then the software for the CCTV is all up to you :)
PCIes sometimes need extra works like adding extra kernel arguments and modules to keep the pcie modules happy. If you are looking to launch a huge product where volumes are expected, then it is worth investigating it since it's cheaper and more compact. However, the power usage is a must for consideration as the USB Accelerator could uses up to 900mA, so that could play a factor.
May I know what host are you trying to attach the accelerators to?
I'm wondering if I can do something like this:
Do some image processing with opencv on my pc, do some math and send data to RaspberyPi to PID controller and then control servos, in real time.
UART wolud be the best connection?
In principle you can use any means to communicate from the PC to the Raspberry PI that are available (UART, ethernet, etc.).
However, you just have to be careful about any time requirements you have in the system you are controlling and check whether the communication rate is suitable.
For instance, you can use 9600 baud UART to temperature control, as the dynamics of such systems are usually slow. If your servos control an inverted pendulum, then the communication speed might make it impossible to control.
I have recently came across an adaptor that would allow me to use laptop memory on my desktop. See item below:
http://www.amazon.co.uk/Laptop-Desktop-Adapter-Connector-Converter/dp/B009N7XX4Q/ref=sr_1_1?ie=UTF8&qid=1382361582&sr=8-1&keywords=Laptop+to+desktop+memory
Both the desktop and the laptop use DDR3.
My question is, are this adapters reliable?
I have 8 GB available and I was wondering if they could be put to use in my gaming rig.
The desktop is an i7 machine generally used for gaming and some basic development.
The adapter should be reliable based on how it looks. There is not much to it only that it extends the "mini" RAM block to a bigger one. You can make the analog with A-B USB cables.
What you should also consider is if both RAM devices use the same frequency and possible heat issues as you will have to cool down the laptop memory more that if it was desktop size. This is because a lot of current goes trough smaller size compared to the desktop based RAM blocks. Then again you have the extension board to handle and disperse some of the heat so if you are not having some really extensive RAM operations you should be fine but you should check what is the working frequency on both of them. For example if the laptop one is faster than the maximum one your computer can support then you won't get that faster performance and the RAM block will work with the frequency of the system bus but if it is slower then the system bus will work on that frequency.
Use standard things on this module as reference to calculate the width. Measure it on image and scale to a reference item and check on your system. Use contacts or the lock in grooves to do the scaling since they are of standard dimensions on all modules. Or the module length...
I'm working on an engineering project where I want a go-kart to maintain a direct connection with a base station. The base and go-kart can be separated by about a half mile (with lots of obstacles in between) which is too far for WiFi.
I'm thinking about using 3G/4G to directly connect the two. Does anyone have any resources or ideas that might help?
Or, alternatively, a better way to connect them? I'm just trying to send some sensor data (pretty low bandwidth) in real-time.
The biggest problem you face is radio spectrum that you are allowed to use. All 3G/4G spectrum is licensed to some firm and they get really unhappy (e.g. have you hunted down and fined) when you transmit in their space.
I did find DASH7 which
is an open source wireless sensor networking standard … which operates in the 433 MHz unlicensed ISM band. DASH7 provides multi-year battery life, range of up to 2 km, indoor location with 1 meter accuracy, low latency for connecting with moving things, a very small open source protocol stack …
with a parts cost around US$ 10. This sounds like it satisfies your requirements and keeps the local constabulary from bothering you.
You could maybe use SMS, between a modem on the kart and a mobile phone or modem at the base.
A mobile data connection like a telephone call isn't possible directly between the two; you have to make a data connection from the kart to a server in your operator's core network, identified by the APN. Then you can access IP addresses as for a normal internet connection - so the base computer would have to be a web server.
My project is to capture images and process them to move a wheelchair accordingly. I am using Nexys2 FPGA board for this purpose. Nexys2 has a usb port and the camera is also a usb camera. but i dont have the drivers in verilog which will make nexys2 and the camera communicate with each other. Please help me ill be very grateful.
Well, if you manage to write a driver for a USB camera in VErilog, you can sell that for a lot of money :)
Well, sarcasm aside, there is NO WAY you can access a USB camera in Verilog, unless you have a USB host implemented in your FPGA and have a CPU controlling it and have a SW driver for that camera.
There are alternatives to this, you can buy a camera which has an FPGA "friendly" connector like this one:
5 Mega Pixel Digital Camera Package
Which comes with the Verilog code that you can use in your project.
Sadly, the USB port on the Digilent Nexus 2 board does not have host capabilities, it can only act as a USB slave. The USB connection on the board is used for powering the board and configuring the FPGA and other onboard peripherals.
The newer Nexus 3 board has a second USB port however it has the same issue in that it can only act in slave mode. Also due to the configuration can only be used for mouse and keyboard input.