One question please.
I have a program that makes analysis of an image coming from a camera (with opencv). It has to take the values from that analysis (at a specific "sampling time") and send it to a microcontroller. The analysis part cant stop making analysis because it will let the system "blind" (thats what we think). So...I have read that to pass values from one file to another, if "return" is used, the program stops that file, so one has to use threads...Is this the best way to adress this problem?. Or is there another way to do it in just one thread??
(The overall idea is to control a machine that uses motors with the analysis from a camera, the question is, should this be done with threads or linearly.)
Thanks in advance.
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I need to do some basic networking for a Pygame project.
Basically, it's a 2D single player or cooperative game. The networking only needs to support two players, with one as a host.
The only information that needs to be sent is the positions of players, creeps and bullets.
I've been reading around and Twisted keeps coming up, but I haven't done networking before, and I'm not sure if that might be an overkill.
So, is it possible for a relative newbie to implement networking in Pygame?
This was asked recently on Reddit, so I'll more or less just copy my answer over from there. I apologize for not being able to provide more links, I have <10 rep so I can only post two at a time.
Twisted might work, but I don't have a whole lot of experience with it. I'd recommend going with sockets, as that's what Twisted uses in the background anyway. Beej's guide (google it) is pretty much the Holy Bible of sockets if you want to learn how they work (in C++, but the concepts extend everywhere). Python does abstract some of the complexity away, but it's still a good idea to know what's going on in the background.
For Python specific sockets, you can go ahead and just use the howto (user745294 posted a link above). Here's a nice article titled "What every programmer needs to know about Game Networking". It goes into the different types of major networking styles (client-server, p2p, udp v. tcp, etc.) and the history behind what some major games used for their networking.
Below is a link to a demo I did on making a networked "game" in Python 2.6/Pygame. It's not actually a game, but each client you create connects to the server and controls a character. You can move your character with the arrow keys and the character will move on all connected clients. I tried commenting the source code with some indication of what I'm sending back and forth, but you may need a little knowledge about sockets to understand it.
The source code is provided in the codepad links in the comment below this post. You will need to provide two images in the same directory as the scripts:
bg.png is the background sprite. It should be an image 400px wide and 300px tall (this can be changed in the GameClient class if needed)
sprite.png is the player character. It should be smaller than the background so that you can see it moving around.
You can use Twisted for networking with Pygame. The "game" project on Launchpad has some examples of how one might integrate the main loops together; basically, use twisted.internet.task.LoopingCall to draw Pygame frames and handle input, while letting the Twisted reactor of your choice run normally.
Since you are already using Pygame, I think this light networking library made for Pygame will do what you need and teach you, but not overwhelm you.
"Mastermind Networking Lib" via pygame.org
There is Pyro (Python remote objects) as another solution for networking in Python.
http://irmen.home.xs4all.nl/pyro/
Using raw sockets is low-level and full of danger. As said before, Twisted is complex and takes to time get up and running. To save yourself some headaches I'd try something like zerorpc.
You need the following solutions:
discovering other player(s) on the (local) network, you don't want player to enter some IP address
handle network errors
serialize messages containing your data (positions, player name, etc.)
handle threading as networking is asynchronous I/O
Above should still be called 'basic', you should really use some fancy networking library with idiomatic API.
Essentially you need to expose the network service (in its own thread) that will push messages to Python's Queue, and then access this same queue from your Pygame code, and if there is a message then you update whatever structures you use to store player's position and draw it on screen.
You shouldn't send stuff like bullet positions over the network as they can be easily (and faster) calculated locally. You just send an event like bullet_shot over the network with a source position and velocity vector.
I'm working on the sound part of an interactive installation that would need an event to be triggered by osc an undefined number of times, making the sound linked to it overlaps instead of being rewinded and started again.
Would it be possible to do that without needing to make an array of loadings of the same sound?
I'm actually trying to do it with processing and minim library.
Do you think it would be easier to achieve it with another programming software? I've found myself in the same difficulties trying to do it with puredata. Any tip or clue would be extremely welcome.
Thanks a lot.
You will need multiple readers ([tabread~] resp [tabplay~] in Pd; i don't know about Processing/minim, but the same principle applies) to read the table multiple times (in parallel), where each one can be started separately.
However, you only need a single instance of your data array (e.g. [table]), as the various readers can access the same array independently.
Can you use Java libraries in Processing? Processing is built on Java, yes?
If you can, I have a library you can use, supporting a class I call AudioCue available via github. This is modeled on a Java Clip but with additional capabilities. It allows multiple, concurrent playback. AudioCue also has real time controls for volume, panning and playback speed, in case you want to play around with adding some more interactivity to your installation.
I would love to know if it can be used with Processing. Please follow up with me if you try this route. I'd like to see it done, and can possibly assist.
If Processing allows you to send PCM directly out for playback, then the basic algorithm is the store the audio data in an array, and create pointers or cursors (depending on your preferred terminology) that independently iterate through that array. This is the main basis of the algorithm I use for AudioCue, with the PCM being routed out via a Java SourceDataLine.
I've been trying to find a way to capture keyboard input during runtime simulation of my Verilog code. Is this even possible?
I have taken a look at resources like asic-world and the Quick Reference for Verilog found on Google, but found nothing regarding a way to take keyboard inputs.
There seems to be a fundamental misunderstanding here in the difference between a hardware description language used to simulate a design versus using that same description to implement a design in actual hardware. It's like drawing a picture of a pinwheel, blowing on that picture, and expecting the pinwheel to start turning.
You can certainly build a 3-D model of that pinwheel, simulate the force of the wind on that model and watch it turn, and then send that model to a 3-d printer to get your pinwheel. I suppose you could put wind sensors in front of your monitor, and write a program that converts a value from the sensor to a value used in the simulation. The point is, the simulator has no knowledge that the value came from someone blowing on the monitor, it just sees a parameter value change.
Unless you are designing the keyboard hardware yourself and simulating that, there really is not much point in taking keyboard input from a computer and using that to stimulate your design in simulation. The operating system has already abstracted away the keyboard hardware and provides you with a string of character codes. The reason you are simulating in the first place is to verify the functionality of your design. If you find a problem, you are going to want to replay the exact same stimulus until you fix your problem.
Just like the pinwheel example, I do know it's possible for someone to set up a program that reads keyboard input and provides that as stimulus to a simulation. But that involves inter-process communication(IPC) and specific tool knowledge to set that up.
I'm trying to interface a Nexys3 board with a VmodTFT via a VHDCI connector. I am pretty new to FPGA design, and although I have experience with micro-controllers. I am trying to approach the whole problem as a FSM. However, I've been stuck on this for quite some time now. What signals constitute my power up sequence? When do I start sampling data? I've looked at the relevant datasheets and they don't make things very clearer. Any help would be greatly appreciated (P.S : I use Verilog for the design).
EDIT:
Sorry for the vagueness of my question. Here's specifically what I am looking at.
For starters, I am going to overlook the touch module. I want to look at the whole setup as a FSM. I am assuming the following states:
1. Setup connection or handshake signals
2. Switch on the LCD
3. Receive pixel data
4. Display video
5. Power off the LCD
Would this be a reasonable FSM? My main concerns are with interpreting the signals. Table 5 in the VmodTFT_rm manual shows a list of signals; however, I am having trouble understanding what signals are for what (This is my first time with display modules). I am going to assume everything prefixed with TFT_ is for the display and everything with TP_ is for the touch panel (Please correct me if I'm wrong). So what signals would I be changing in each state and what would act as inputs?
Now what changes should I make to accommodate the touch panel too?
I understand I am probably asking for too much, but I would greatly appreciate a push in the right direction as I am pretty stuck with this for a long time.
Your question could be filled out a little better, it's not clear exactly what's giving you trouble.
I see two relevant docs online (you may have seen these):
Schematic: https://digilentinc.com/Data/Products/VMOD-TFT/VmodTFT_sch.pdf
User Guide: https://digilentinc.com/Data/Products/VMOD-TFT/VmodTFT_rm.pdf
The user guide explains what signals are part of the Power up sequence
you must wait between 0.5ms and 100ms after driving TFT-EN before you can drive DE and the pixel bus
You must wait 0 to 200ms after setting up valid pixel data to enable the display (with DISP)
You must wait 160ms after enabling DISP before you start pulsing LED-EN (PWM controls the backlight)
Admittedly the documentation doesn't look great and some of the signals names are not consistent, but I think you can figure it out from there.
After looking at the user guide to understand what the signals do, look at the schematic to find the mapping between the signal names and the VHDCI pinout. Then when you connect the VHDCI pinout to your FPGA, look at your FPGA's manual to find mapping between pins on the VHDCI connector and balls of the FPGA, and then you can use the fpga's configuration settings to map an FPGA ball to a logical verilog input to your top module.
Hope that clears things up a bit, but please clarify your question about what you don't understand.
This is one of my assignments and I need some help in getting started. The basic idea behind the assignment is that I have to design a self destructible email program that is capable of destructing the message after (n) time duration.
Speaking about self destructible emails, there are quite a few ones on the internet offering the same service. But what they do is, they just convert the email message into an image and store them on their servers. Now, they send the message attaching the image inline with it. After they receive a hit on that image (which means that the message was being opened), they simply delete the image and the inline image link breaks! BOOM!
IMO, that's not what a self destructing email should be like. Nevertheless, in my case, I have to take care of following points:
I have to do it for TEXT. No image, nothing else.
I have to assume that the systems used throughout the process will be UNIX based (I don't know how that is going to make a difference).
There are also some hints regarding the usage of various network layers in solving the problem.
This isn't supposed to be done "in general". What I mean by that is, I have to do that ONLY for one/two UNIX systems. Let me put it this way, all I have is two UNIX systems and nothing else. Now I want to create a program (in UNIX itself) that would do that self-destructing thing. I have total control of protocols and the network layers and I have to code anything and everything required at any level.
This is more geared towards the StackOverflow side of things but I have no problem getting you started.
The first thing I'd like to point out is that you seem to be heavily over-analyzing this. The services that have self-destructing e-mails which are image based are simply deleting a file after it is viewed. All you need to do differently is put that text in a file and get it's contents before deleting it. This fits well with the UNIX philosophy since so many programs already make use of flat files.
The part you seem to have left out is how you are building this. You describe it as an e-mail program and then talk about web services. Is this a web-based project or a program you are designing for Linux? Do you have to code everything from scratch or can you parse output from Linux utilities to grab the mail? These kinds of things really would simplify the process.