I live in a building where the laundry machine is a bit far away from my suite. There is only one machine there so only one person can use it at a time. Quite often I take my laundry there just to realize that the machine is in use so I have to go back defeated and try again later. I want to build a doodad that can detect when the machine is in use and broadcast that information throughout the building so that I know that the machine will be available before I go there.
This question is not about how to build the detector. I am planning on using a raspberry pi somehow. This question is about what do I do when I detect that the machine is in use. How do I broadcast that information mainly to myself or potentially to anyone in the building?
I need a cheap solution (< $100). It has to be wireless. The signal has to travel approximately 30 meters in one direction. The broadcast should be readable on any laptop or cell phone (not a requirement but nice to have).
I was considering making an android app using WiFi direct. I'm sure others in the building would be interested in this app and I can use them as peers to extend the range of the broadcast. But I don't like this solution because I know that wifi direct doesn't work with iOS devices. Also this solution will require others to side-load an apk which they might not know how to do.
Please let me know if you can come up with something a bit less reliant on p2p and more platform independent.
Related
As a final school-graduation project I try to develop a kind of spying-car. Which means there is an iPhone placed on a little LEGO-car and an iPad used as a "steering wheel" for the car. Also it is planned to transmit Audio and Video from the iPhone's microphone/camera to the iPad (more than the steering data vice versa).
In the first place the connection from iOS to iOS should be established over a local WiFi network and later - if possible - over 3G (by using the iOS devices network-IP and a DNS server to deal with frequently changing addresses).
My question is: which technology do you recommend using? I read about GameKit, peer-to-peer and so on, but I think these technologies are too abstract for later being able to communicate over 3G. I guess I need to go a little deeper into the low levels of the communication progress. Any suggestion that could bring me a step forward is highly appreciated! (also regarding other parts of my project)
One more thing: Some user suggested using a third party service and to route the sent (video) data over an external server. If possible, I'd rather not use any "middle man". It should just be a basic server-client communication where the iPad is the server and the iPhone the client.
It is kind of an open ended question, but interesting.
First of all, GameKit do have 3g p2p support, see here:
https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/GameKit_Guide/Matchmaking/Matchmaking.html
It will handle the peer-to-peer addressing and establisment of the socket. It can also handle voice chat, but I personally never tried this feature so I can't say if it is feasible in your case.
One idea is to leverage existing video-chat services. This will give you a low-latency audio/video channel with peer-to-peer addressing (well, likely using a central server).
Apple's FaceTime is such a service, but there is no public API to it (AFAIK). Same goes for Skype and Google.
There are some paid services that look like they have nice iOS APIs:
http://tokbox.com/platform
http://docs.weemo.com/sdk/ios/
You have to figure out a way to transmit control commands to the peer iPhone, I did not see if the services above had any possibility of sending text messages/arbitrary data.
Tokbox has a free trial so you could try it out and see if it works for you.
I would go for GameKit if this is a hobby project on a budget and there is time for hacking, and probably look into a more high-level API if there is a deadline...
sorry for writing this as an answer, but i don't have enough rep to comment...
i'm working on a similar project and i currently don't have any advice regrading video-streaming, however, from what i read (extensively) i came to the conclusion that i need to use p2p connection between devices for better performance and use socket programming in order to achieve this (although not the most easy to implement choice).
I considered using GameKit which i think will probably answer most of your needs as Krumelur pointed out. but in my case, eventually the app will be cross platform so i had to use low level network programming. you can check out my question here to see the sources i used to try and make the connection between 2 peers, hopefully you'll have better luck than me...
For those not in the know, Spaceteam is a very popular and very fun multiplayer game for iOS.
It allows for real time gameplay among multiple devices on an ad-hoc Wifi network - how does it do this?
Are there published libraries describing how to build protocols on top of ad-hoc networking libraries? Is it iOS specific, or would it be possible to build a variety of applications across different platforms?
Quickly, answer before we hit the asteroid!
Specifically which aspect are you interested in? There's nothing particularly special about mobile devices or ad hoc Wi-Fi networks (except in an ad hoc network, not all devices may be able to communicate with each other, so some mesh networking can help but unnecessarily complicates matters for the normal case).
I'll answer the broader question first, because it's more interesting. In my experience, there are a handful of major considerations:
Server/client or peer-to-peer? By this I mean whether there's a "master" deciding the true state of the world and communicating this to all clients. Avara is the only game I know of that is "peer-to-peer" in this sense (peers sent commands to all other peers; this proved bandwidth-heavy for modem users on 6-player games). I am not aware of games using more sophisticated network topologies to communicate game state (e.g. only sending data to one client on each LAN).
What do you do about latency? Avara is the only game I know of which lags everyone locally by the "latency tolerance" in order to get a consistent state of the world, which was terrible if someone was on a modem (turning off compression helped a lot). There are various ways to do "latency compensation" (e.g. in Half-Life/CS), some of which could also work on peer-to-peer games.
Time sync? For client-server games, you at least need to worry about a changing RTT. For peer-to-peer games, I think you also want to agree on timing that minimizes the effective maximum latency.
What if clients disagree about the state of the world? Avara just lets peers decide on their own state of the world (and displays "reality fragmentation detected" if it senses a mismatch, which might happen due to dropped packets or a too-low "latency tolerance").
What if a player leaves? For a P2P game, you might have to agree on a consistent game state (e.g. if the player was disconnected after sending commands to a subset of other peers). For a client-server game, you might have to elect a new master.
And now, after watching the Spaceteam trailer:
I have no idea how it works, since I haven't reverse-engineered the protocol. However, it's pretty simple to make something that works well enough:
Use some sort of P2P discovery to find players (e.g. Bonjour; there should be plenty of docs and samples out there).
Communicate with peers. I've done this with GameKit circa iOS 3/4 (I'm not sure if it still works over Wi-Fi).
Elect a master. This can be as simple as whoever presses "ready" last attempts to be the master. In some edge cases you might have to handle failure.
Let the master decide everything. Spaceteam is not latency-sensitive; Wi-Fi latency tends to be at most a handful of milliseconds, and nobody's really going to notice if one device is slower by 100 ms (as long as the UI responds fast enough).
There is a library made by Spaceteam that does this for Unity games.
https://github.com/hengineer/CaptainsMess
The creator of Spaceteam also wrote an old blog post about Networking in Spaceteam
http://spaceteamadmirals.club/blog/the-spaceteam-networking-post/
There is an iOS only library that will connect nearby devices easily called MultipeerConnectivity https://developer.apple.com/documentation/multipeerconnectivity
If you want something that will work cross-platform I have an example app here: https://github.com/brendaninnis/LocalNetworkingApp, which I explain in great detail here: http://brendaninnis.ca/connect-nearby-devices-part-1.html
I'm nxj beginner.
I have some questions about bluetooth communication between PC and brick.
First, when bluetooth communication occurs, where is the birthplace processing this datas?
In other words, I want to know whether these datas will be processed on CPU or brick.
Second, what is exact roles CPU and brick in bluethooth communication?
That means what is processed on CPU and what is processed on brick.
I have searched almost web site but I can't find this anywhere.
Please help me. Thanks.
You can see it in the package structure.
lejos.nxt.*
This package contains classes running on the NXT-brick. All code in this package will be compiled for the brick and will run on the brick.
lejos.pc.*
Here the difference is not that clear. This is java-code you compile for personal computer. So most code runs on your computer. But some classes (e.g: RemoteMotorController) only send messages to the NXT-brick which gives commands to the motors.
lejos.pc.comm provides API's that allow you to communicate/control the nxt robot from the PC.
When importing the the libs to an Android project, it allows you to build an instance of the same environment used on a pc, but within android.
I agree it can be tough finding some things out. It would be great if there was as stronger lejos presence on SO
This question is months old and has remained un-answered I actually have a lot of questions about it myself, but I might be able to provide some insight for utter novices.
when using bluetooth with Android and NXJ robots, you use either lejos.pc.comm or lejos.NXJ.
Both provide APi's to do almost the same thing, but work a little differently. I don't know nearly enough about the NXJ api, but I do know that it is the one that lets you manipulate the robot much more effectively, such as outputting data to it's LCD screen, which you can't do with the pc.comm api
As far as I can tell, the pc.comm API uses both Android Bluetooth API's and it's own protocols to allow communication with Lego LCP commands.
(I want to come back to this, but I'm writing a dissert on the topic so I'll try to update it in a couple of days. Seems not many are interested though, shame)
I want to port a good OpenCV code on an embedded platform. Earlier such stuffs were very difficult to perform but now TI has come up with nice embedded platforms which are comparatively hassle free as they say.
I want to know following things:
Given that :
The OpenCV code is already running on PC smoothly. (obviously)
Need to determine these before purchasing the device.
Can't put the code here in stackoverflow. :P
To chose from Texas Instruments: C6000.
Questions:
How to make it sure that the porting will be done?
What steps to be taken to make it sure that after porting the code, will run (at least).
to determine whether the code might require some changes to make its run smooth.
The point 3 above is optional.
I need info which will at least give me some start up in this regard.
What I thought I should do?
I am to list the inbuilt functions down.
Then to find available online bench marking for those functions for the particular device like as shown towards the end of this doc.
...
Need to know how to proceed further?
However C6-Integra™ DSP+ARM Processor seems the best.
The best you can do is to try a device simulator (if it is available), but what you'll see there is far from perfect.
Actually, nothing can tell you how fast and how well the app will run on the embedded device before running you specific app on that specific device.
So:
Step 1 Buy it
Step 2 Try it
Things to consider:
embedded CPU architecture: Your app needs a big cache? how big is the embedded cache?
algorithm: do you use a lot of floating point operations? how good is the device at floating point ops?
do you have memory transfers? data bus on a PC is waaay faster than on embedded
hardware support: do you use a lot of double-precision calculations? they are emulated on ARMs. They are gonna kill your app (from millisecons on a PC it can go to seconds on a ARM)
Acceleration. Do your functions use SSE? (many OpenCV funcs are SSEd, even if you don't know). Do you have the NEON counterpart? (OpenCV does not have much support for that). The difference can be orders of magnitude from x86 SSE to embedded without NEON.
and many, many others.
So, again: no one can tell you how it will work. Just the combination between the specific app and the real device tells the truth.
even a run on a similar device is not relevant. It can run smoothly on a given processor, and with another, with similar freq or listed memory, it will slow down too much
This is an interesting question but run is a very generic word in this context, therefore I feel the need to break it down to other 2 questions:
Will it compile in an embedded device?
Will it run as fast/smooth as in a PC?
I've used OpenCV in a lot of different devices, including ARM, SH4, MIPS and I found out that sometimes the manufacturer of the device itself provides a compiled version of OpenCV (for my surprise), which is great. That's something you can look into, maybe the manufacturer of your device provide OpenCV binaries.
There's no way to know for sure how smooth your OpenCV application will be on the target device unless you are able to find some benchmark of OpenCV running in there. PCs have far better processing power than embedded devices, so you can expect less performance from the target device.
There are 3rd party applications like opencv-performance, that you can use to test/benchmark the environment once you get your hands on it. And if performance is such a big deal in this project, you might also be interested in this nice article which explain some timing tests done on couple of OpenCV features comparing implementations using the C and C++ interfaces of OpenCV.
Is it possible to get location data out of Google Gears, Google Gelocation API or any other web location API (such as Fire Eagle) in such a format that it appears to other software as a GPS device?
It occured to me reading these answers to my question regarding WiFi location finding, on Super User, that if I could emulate a GPS unit, many of these web services could act as a 'poor-mans' GPS to otherwise less useful software that requires it.
Is GPSD an option?
Preferably OSX & Python, but I would be interested in any implementation.
There is a very similar thread on a Python mailinglist that mentions Windows virtual COM ports and discusses Unix's pseudo-tty capabilities. If the app(s) you want to use let you type in a specific tty device file, this may be the easiest route. (Short of asking the authors to provide a plugin API for what you're trying to do, or buying yourself a $20 bluetooth GPS mouse.)
Are you using OS X?
There is a project macosxvirtualserialport on Google code that provides a graphical wrapper around some of the features of a utility called socat. I'd recommend taking a look at socat if you see potential in the pseudo-tty route. I believe you could use socat to link a pipe from a Python program to a pseudo-tty.
Most native Mac apps will be querying IOServiceMatching for a device with kIOSerialBSDRS232Type, and I doubt that a pseudo-tty will show up as an IOKit service.
In this case, unless you can find a project that has already implemented such a thing, you will need to implement a driver as described in this How to create virtual COM port thread. If you're going to the trouble of create a device driver, you would want to base it on IOKit because of that likely IOServiceMatching query. You can find the Apple16X50Serial project mentioned in that post at the top of Apple's open source code list (go to the main page and pick an older OS release if you want to target something pre-10.6).
If your app is most useful with realtime data (e.g. the RouteBuddy app mentioned in the Python mailinglist thread can log current positions) then you will want to fetch updates from your web sources (hopefully they support long-polling) and convert them to basic NMEA RMC sentences. You do not want to do this from inside your driver code. Instead, divide your work up into kernel-land and user-land pieces that can communicate, and put as little of the code as possible into the kernel part.
If you want to let apps both read and write to these web services, your best bet would probably be to simulate a Garmin device. Garmin has more-or-less documented their protocol in the IntfSpec.pdf file included with their Device Interface SDK. Again, you'd want to split as much as you could into user-space code.
I was unable to find a project or utility that implements the kernel side of an IOKit-based virtual serial interface, but I'd be surprised if there wasn't one hiding somewhere out there. Unfortunately, most of the answers I found to that question were like this, with the developer being told to get busy writing a kext.
I'm not exactly sure how to accomplish what you're asking, but I may be able to lend some insight as to how you might begin to get it done. So here goes:
A GPS device shows up to most systems as nothing more than a serial device -- a.k.a. a COM port if you're dealing with Windows, /dev/ttySx if you're in *nix. By definition, a serial port's specific duty is to stream data across a bus, one block at a time. So, it would then follow logically that if you want to emulate the presence of a GPS device, you should gather the data you're consuming and put it into a stream that somehow acts like an active serial port.
There are, however, some complications you might want to consider:
Most GPS devices don't just send out location data; there's also information on satellite locations, fix quality, bearing, and so on. Then again, nobody's made any rules saying you have to make all that data available. There's probably more to this, but I'll admit that I need to do more research in this area myself.
I'm not sure how fast you can receive data when dealing with Google Latitude, etc., but any delays in receiving would definitely result in visible pauses in your "serial port"'s data stream. Again, this may not be as big a complication as it seems, because GPS devices are known to "burst" data across the bus anyway, but I'd definitely keep an eye on that. You want to make sure there's always a surplus of data coming across, not a shortage.
Along the way you'll also have to transform the coordinates you receive into valid GPS sentences, as well. You can find specifications for those, but I would definitely make friends with the NMEA standard -- even though it is a flawed standard, it's the one everyone seems to agree on anyway.
Hope this helped you, at least a little bit. Are there anymore details specific to your problem that you think could be useful in answering this question?
Take a look to Franson GPS Gate which allows you to connect to Google Earth among other things (like simulating GPS and so on). Is windows only though but I think you could get some useful ideas from it.
I haven't looked into it very much, but have you considered using Skyhook's SDK? It might provide you with some of what you are looking for. It's available for every major desktop and mobile OS.