raspberry-pi - How do I use system time as a trigger in codesys ladder?

Question

Programming a raspberry pi with codesys, using mostly ladder, basically I need to write all data that is currently in a couple arrays to a csv file at midnight, so i'd like to be able to use a dt value as a trigger. I can't figure out how to use that value in ladder, however. I can display the local time on visualizer, but if i wanted something like "if localTime=#value" then coil 'Write' turns on, where is the actual variable for system time?

Answer 1

据我所知，您需要使用功能块从本地系统读取时钟，例如GetDateAndTime来自CAA DTUtil Extern Library。然后，您需要使用功能块（例如标准库RTC中的功能块）使其保持最新状态

下面读取系统本地时间，然后用RTC功能块对其进行更新。至少在 Windows 上工作，无法用 Raspberry 进行测试。请注意，如果本地时间因某种原因发生更改，则不会再次更新。因此，例如，您需要时不时地运行GetDateAndTime呼叫。

首先，一个更新并提供本地时间的程序：

PROGRAM PRG_UpdateSystemTime
VAR_OUTPUT
    SystemDateTime      : DT;
END_VAR
VAR
    ReadLocalTime       : DTU.GetDateAndTime; //Reads local time from system
    RtcBlock            : RTC; //Real-time clock - updates the previously received local time
END_VAR

//NOTE: Output is UTC time

//The block that reads local time. NOTE: Error handling is missing
ReadLocalTime(xExecute:= TRUE);

//Running real-time clock
RtcBlock(
    EN  := ReadLocalTime.xDone AND NOT ReadLocalTime.xError,
    PDT := ReadLocalTime.dtDateAndTime,
    CDT => SystemDateTime 
);

然后是梯子的一个例子。我认为有数百万种方法。请注意，“DoSomething”将在整个秒内为 TRUE，因此您可能应该使用上升沿检测。