https://forge.codesys.com/forge/talk/Runtime/thread/d2c0450a44/2020-02-27T16:56:54.996000ZRecent posts to RS232 maximizing communication speed?2020-02-27T16:56:54.996000Z2020-02-27T16:56:54.996000ZLMDaniel999https://forge.codesys.com/u/lmdaniel999/https://forge.codesys.comef721e3b20a01130eca32f07381974c615cc4fb3

<div class="markdown_content"><p>Hi,</p> <p>i got a question about the serial communication in Codesys with the raspberry pi and an usb/serial converter:<br/> <strong>How can i maximize the communication speed?</strong><br/> I request a measuring value by sending a symbol to an measuring system.</p> <p>More infos about the setting:<br/> For sending and reading I use an edited SERIAL_LINE function block, i got at this thread: <a class="" href="https://forum.codesys.com/viewtopic.php?t=5699" rel="nofollow">https://forum.codesys.com/viewtopic.php?t=5699</a><br/> i added a new mode, wich sends first and reads the returning value after sending the request symbol.<br/> The waiting timers in the serial connection I minimized to 80ms. If I use shorter times, I get no values.<br/> Also I tried different values for the timers after sending and reading and tried different cycle times down to 8ms.<br/> Changing the cycle times and waiting times simultaneously didn´t work, too.</p> <p>The baud rate of the measuring system is fixed to 4800 baud.<br/> It uses 7 bits, even parity and 2 stop bits.<br/> If I send a "?", i get a value back like this: "+xxx.xxx$R"</p> <p>Requesting and reading a value takes at least about 200ms.<br/> So i can only transfer 5 values a second, but i need a faster communication.</p> <p>How can I improve the communication speed?<br/> I know that there are limits for this communication, but I want to know where´s the problem and the bottleneck.<br/> At another sample I read, that the serial communication can only transfer one symbol at one cycle. Is this right? The 80ms waiting time seems to fit to this expectation...<br/> If this is true, why the communication can´t be improved by reducing the cycle time?<br/> The baud rate might be big enough to transfer more values a second...</p> <p>Or is the serial communication implemented in the raspbian os?</p> <p>Why does the serial communication need the waiting timers?</p> <p>Thanks a lot! </p></div>