5/14/2019 0 Comments Qt Serial Port Baud Rates 115200[quote author='arianoo' date=']it means that when i get notified that data is available on the port by ready read and call readAll immediately,it reads the data incorrectly while i see what there is on my port the function has changed it.what should i do?[/quote] The readyRead signal is issued when some data ist available. Ac run active content js. This does not mean the sequence is already completed. As a matter of fact with low baud rates it might take considerable time to receive even short sequences. As I understand your data is partially corrupted, but not completely. This does not sound like a wrong baud rate, but may be other settings as suggestesd above. The question is what you are trying to achieve. If you want to communicate as in a dialog with a device, the approach with readAll may be feasible. Providing that the sequences send by the other device are reasonably short. You may wait some time after you have received readyRead and then start reading (e.g. However, in my opinion this approach will be very fast at its limits. If you have varying length of information which cannot be determined beforehand. The higher rates 115200 upwards (once again doubling starting at 57600) are used for hard-wired connections. As mikeselectricstuff mentioned, 14400 and 28800 bps were introduced as 1.5 x 9600 and 1.5 x 19200 when modems speeds couldn't be doubled at the time, but are seldom used anymore. In computing, a serial port is a serial communication interface through which information transfers in or out one bit at a time (in contrast to a parallel port). Throughout most of the history of personal computers. Especially, if you are doing some real-time communication with some sensor sending information at specific rate but different information length, you will run into trouble. I would read the device in smaller chunks and store the data in a buffer myself. You may do this bytewise or in chunks based on the return of bytesAvailable. Thank u all so much for considering my question and answering it. The settings of the port are all correct as i am able to communicate with devices by the commands i send to them and i also monitor the port by an interface device with the same settings and it works correctly and the problem is absolutely the way i read data from the port. Dear koahnig u have mentioned many points that can help me understand how serial ports work,the bytesAvailable function always returns exactly the number of bytes that readAll would read and i have tried to read that size of data each time with read() function and it hasnt helped problem with waiting is that for a good result and a high percentage of getting correct data i have to wait 3 seconds every time something is available on my port and it makes my program run too slow.i was using this approach up to last week but its really impossible to have this much delay. The way that has answered for me by now and is not yet reliable at all, is that i am opening the port in buffered mode and calling readall. Most of the times it returns the exact data which is available on the port but this also has its own problems. Im truely confused with this issue i have to work with two different devices through serial port and getting correct data from them is so important for me:( ill be thankfull if u tell me the ideas that come to ur mind so that my problem gets fixed. Thanks alot for your attention. Dear arianoo at first I like to mention two major differences. The experiences I collected on windows and wince. Futhermore, I had retrieved an old version of QExtSerialDevice. The project has been part of SourceForge at a time. Later I have found out that the project has been moved to google. I just saw that you are refering to QSerialDevice. I do not know if the roots are the same. However, it seem to be newer than QExtSerialDevice. I have a program reading data from a device in real-time. The information is of the form prefix-data-suffix. Initially the program used only TCP/IP for reading the data. It basically scans the input for the starting bytes of the prefix where also the also the complete record length can be found. This led to reading the input bytewise until the starting character found. The remainder will be read bytewise as well until bytesAvailable are read or the complete record has been received. The collected record will be processed immediately. Initially QExtSerialDevice could substitute the QTcpSocket since both are derived from QIODevice. The only difference was the opposite definition of atEnd() in QExtSerialDevice. Later I ported to WinCE where the API functions are completely different. Nevertheless, I maintained the bytewise copying process. A port to linux never happened and probably will never. Since the information records are rather short, it was never an issue with TCP/IP. Depending on the baudrate it becomes an issue with serial comms. I personally would prefer the bytewise reading especialyl for my application. I need to buffer anyway, because half a record is a lost record. I have no experience with QSerialDevice. Probably the readAll implementation is save, but I would be careful until I know. Only the developers working on it can tell what is happening during readAll and additional information is received. Or you have to dig into that yourself. Hi Koahnig I'm really thankful for your post i read it 10 days ago but didn't have time to your advice I started using buffered mode but I still have to add some delay before reading long data because if i read it immediately it gets damaged I also increased the time of setcharintervaltimeout which i don't know what exactly it does and i didn't realize if it changed anything.I want to thank u again cuz your ideas and information u wrote were truely helpful for me.
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