Sorry for my bad english first.
I'm currently working on an Arduino project which is really simple.
I'm working on an attendance logger for my school to know how much time students are spending studying.
The RFID Reader part is working fine. When a tag is detected, I'm storing the value and the time in a SD Card.
Every hour, my system have to send the logs to a web server to store it in a database and here come my problem. I'm struggling with the ethernet part.
Indeed, when I'm performing a HTTP Request, my sketch is "blocked" and students can't use the system anymore.
It's a real big problem, because if there are like 200 lines in my logs, sending those throught a request, one by one, will take really long.
I'm already aware of using millis() to use "multi-tasking".
I have absolutly no idea about how to send requests without "blocking" my sketch.. I'm not looking for someone to write my sketch. I just want to know if there is a way to avoid the "blocking" effect of the ethernet shield when I'm performing a request.
Thanks for your help.
Even if you send one by one, you dont have control over the server side. you have no gurantee that the server will Always response within a certain timeframe.
if your system is very busy, then this may not be your perfect solution.
on other hand, just a thought though, (I dont have personal experience with ethernet shield.)
you could send data serially from first arduino to second ardiuno, individually, every time RFID is detected. This should not take much time compare to the time to send 100 lines of logs. Now, one by one, second ardiuno can save these data in its memory until it is finally sent to server.
now when second arduino is busy sending data to server, we can collect some those RFID reading in first arduino's memory, and pass to, when the things with server is done.
to check if second arduino is bg, we could set a pin high in second arduino until the server part is done.
but still, I dont see why do you have to send it every one hour. I am asuming you have your reason.
If you still want to save some time, the make a parallel data transfer between two arduino, instead of serially.
Related
I am a beginner in Android and testing Android code in which I am receiving and sending data through UART communication.
Hardware for communication- MAX232 device which is connected to Raspberry Pi3 Model B and the other part of MAX232 is connected to Vending Machine Port(Rx,Tx,Gnd to communicate my android app with the Vending Machine). My communication breaks SPORADICALLY and then starts communicating.
I do not know what the reason is
If anyone can help me in this, please suggest. Or any other information will be needed,I will share
private static final String UART_DEVICE_NAME = "UART0"; // define in my code.
**
I have to use ttyAMA0(PL011 UART) port because baudrate does not
change with the core frequency like with ttyS0(MIniUART)
**
For example: If I send 100 commands one by one, I get 2-5 times this
error.
**
> ERROR: Failed to open /dev/ttyAMA0: No such file or directory
**
Same thing happens to me reading data. I do not talk to the device (particle photon) connected to it, just listen. Since i'm expecting a response frequently, anything more than a couple seconds means things have gone south on one side or the other. It didn't seem likely though that my photon code was bad, as I had done many day-long tests with other things reading the data (arduino IDE, whatever).
Anyway, I created a runnable that fires every few seconds and checks when the last received response was. If it exceeds 60 seconds (things are most certainly wrecked and not going to get any better), I'll attempt to start up the connection again (Periperhal manager's openUartDevice). The main code waits another 60 seconds before trying again if it still has not received a response.
I also added code in 'onUartDeviceError' to trigger a callback the second that goes bad (not really sure if that's ever been the culprit in this), which will attempt the same restart logic but with a much smaller wait (like 5 seconds).
Lastly I made the Pi reboot itself (and thus the attached photon) so everything starts fresh, every morning at 6am. This has solved the issue for my purposes and its been in service for somewhere in the neighborhood of two years. Due to this reliability issue I don't do anything important with the pi, it simply exists to aggregate data from a few places and provide JSON. The photon is much more reliable even if the pi stops listening to it, so it controls the important/dangerous stuff (heaters, lithium batteries). Hopes this helps a little, but maybe some reconnect logic would solve the problem.
We have a system with two micro-controllers and we are developing a simulation environment. In the real system the micro-controllers communicate trough UARTs sending small data back and forth all the time every millisecond (asking for variable values, sending commands, etc.).
In the simulation each micro-controller is a different application and we must find a way to communicate them. I have tried TCP/IP before but I notice from time to time there are very long time delays - for example it works ok and after 20 messages there is a second delay. I assume this is because TCP/IP is not designed to send small packets of ~10 bytes of data every millisecond. I have found some information about the issue but nothing conclusive on how to avoid the problem.
I was wondering if NamedPipes will work better. Will there be a huge performance hit when using NamedPipes to communicate back and forth ~10 bytes of data every ms? Should we look into another alternative? In the past the company has used virtual serial ports but that requires special third-party software and is too cumbersome to set up.
I'm working with 2 little machines with limited unix tools. Both are conected between each other via serial. I'm transfering binary data, so the devices are on raw mode. The sending machine is sending files to the other one and between there's a delay of X ms (specified as parameter). I would like to know if it's possible to measure those delays on destination machine in order to identify how many files are coming. Till now i was using cat < /dev/ttyS5, but this is not a option to my purpose.
Any idea?
Thanks
IMHO the easiest way is to write a little program which is waiting for bytes on the serial line.
Everytime a character arrives some sort of timer/timestamp is reset.
Another thread could be evaluation this timer/timestamp in a loop and increment a counter if it's larger than a defined value.
But please be aware that you might experience delays from the serial line as there's the kernel and its scheduler "in between". Furthermore you'll need appropriate locking of course!
I get how to calculate ping - current time minus the time stamp of the packet - but how do I create a time stamp in the first place? What synchronized concept of time can I use? Note: I use .NET 2.0.
It could be as simple as when you issue your ping request (I will explain this in more detail in a moment), you make note of the current time, and then, when the server/client responds with a pong, you make note of the time again. Subtracting the pong time from the ping time gives you the amount of time for the communication to go between the two applications.
Wikipedia describes ping in the following way:
In multiplayer online video games, MMOs, MMORPGs, MMOFPSs and FPSs ping (not to be confused with frames per second) refers to the network latency between a player's computer (client), and either the game server or another client (i.e. peer). This could be reported quantitatively as an average time in milliseconds... Rather than using the traditional ICMP echo request and reply packets to determine ping times, game programmers often instead build their own latency detection into existing game packets
What I like to do, is when I make a client and a server, I always write in a simple 'ping/pong' command. In short, a ping request is made by one application, when the other application receives it, and sends back a pong confirmation command. This is good for debugging, but for actual development and depending on the game, I usually piggy back this with a heart beat to make sure everything is running as it should. Hope that helps!
I am doing a measurement project where I send and receive data from numerous devices on my network. The send/receive can be considered fast and intensive, as there is almost no pause and a continuous flow of data. However, the data to/from each device is quite small, on the order of a couple of bytes each. For some reason, I am experiencing a reset of my entire ethernet connection where my internet connection also goes down, and I lose connection to all my devices as well. I have never experienced such a situation and am wondering what are some of the common situations that might lead to resets like this?
Actually, it turns out this had to do with the way I constructed my thread, in which I would create a new socket continuously without discarding the previous one. Stupid right? Well I fixed the code and the ethernet no longer crashes.