我正在尝试从TwinCAT3项目中读取ADS数据流。
我编写的函数应该在CycleCount(来自SPS)更改其值时读取数据流-因此CycleCount是回调函数的触发器,并且每毫秒检查一次更改。
要读取的数据流由包含两个值“ nCycleCount”(DWORD-4Bytes)和“ TStamp”(ULINT-8Bytes)的结构组成。因此,整个流包含12个字节的数据。
TwinCAT中的一个周期配置为0.5毫秒,因此变量CycleCount应该每秒更改2次(如果PLC任务的周期时间为一个周期刻度)。当我的程序每毫秒检查一次变量CycleCount是否更改时,应每毫秒调用一次回调函数,并将时间戳记写入Buffer(“ myBuffer”)。但我注意到,在2秒的运行时间中,我仅收到1000个值(而不是预期的2000个值),而我找不到原因?
TwinCAT3中的PLC任务似乎显示了正确的值,但是当用MatLab读取它们时,时间戳值是不正确的,并且并非如前所述是每毫秒:
这些是Matlab的一些输出,其中CycleCounter被写入第1列,时间戳被写入第2列:
我在TwinCAT中使用以下代码来定义结构和主程序:
结构:
TYPE ST_CC :
STRUCT
nCycleCount : DWORD; //4Bytes
TStamp : ULINT; //8Bytes
//Stream with 12Bytes total
END_STRUCT
END_TYPE
MAIN_CC(用于PlcTask):
PROGRAM MAIN_CC
VAR
CC_struct : ST_CC;
END_VAR;
CC_struct.nCycleCount := _TaskInfo[1].CycleCount;
CC_struct.TStamp := IO_Mapping.ulint_i_TimeStamp;
要在通知上读取流的Matlab代码:
function ReadTwinCAT()
%% Import Ads.dll
AdsAssembly = NET.addAssembly('D:\TwinCat3\AdsApi\.NET\v4.0.30319\TwinCAT.Ads.dll');
import TwinCAT.Ads.*;
%% Create TcAdsClient instance
tcClient = TcAdsClient;
%% Connect to ADS port 851 on the local machine
tcClient.Connect(851);
%% ADS Device Notifications variables
% ADS stream
dataStream = AdsStream(12); %12Bytes necessary
% reader
binRead = AdsBinaryReader(dataStream);
% Variable to trigger notification
CCount = 'MAIN_CC.CC_struct.nCycleCount';
%% Create unique variable handles for structure
try
st_handle = tcClient.CreateVariableHandle('MAIN_CC.CC_struct');
catch err
tcClient.Dispose();
msgbox(err.message,'Fehler beim Erstellen des Variablenhandles','error');
error(err.message);
end
%% Create buffer for values
myBuffer = {};
MAXBUFFLEN = 1000;
%% Register ADS Device
try
% Register callback function
tcClient.addlistener('AdsNotification',@OnNotification);
% Register notifications
% %AddDeviceNotification( variableName As String,
% dataStream As AdsStream,
% offset As Integer,
% length As Integer (in Byte),
% transMode As AdsTransMode,
% cycleTime As Integer,
% maxDelay As Integer,
% userData As Object)
% Notification handle
hConnect = tcClient.AddDeviceNotification(CCount,dataStream,0,4,AdsTransMode.OnChange,1,0,CCount);
% Listen to ADS notifications for x seconds
pause(2);
catch err
msgbox(err.message,'Error reading array via ADS','error');
disp(['Error registering ADS notifications: ' err.message]);
end
%% Delete ADS notifications
for idx=1:length(hConnect)
tcClient.DeleteDeviceNotification(hConnect(idx));
end
%% Dispose ADS client
tcClient.Dispose();
%% MatlabAdsSample_Notification: OnNotification
function OnNotification(sender, e)
e.DataStream.Position = e.Offset; %Startposition = 0
%% load variables from workspace
hConnect = evalin('caller','hConnect');
binRead = evalin('caller','binRead');
%% assign to ADS variable and convert to string
if( e.NotificationHandle == hConnect )
%% Read timestamp and encodervalues & append to Buffer
tcClient.Read(st_handle, dataStream); %Read structure from stream
%nCycleCount
nCycleCount = binRead.ReadInt32;
[bufflen, ~] = size(myBuffer); %Get current buffer length
myBuffer{bufflen+1,1} = nCycleCount;
%Read & Append Timestamp to Buffer
tstamp = binRead.ReadInt64; %Read tstamp from dataStream and shift reading position by 8bytes (int64)
myBuffer{bufflen+1,2} = tstamp;
if bufflen < MAXBUFFLEN-1
return;
else
assignin('base','myBuffer', myBuffer);
disp("buffer assigned in workspace")
myBuffer = {}; %empty Buffer
end
else
%do nothing
end
end
希望您能帮助我解决我的问题-提前致谢!
据我所知,您的程序运行正常。
1)
您正在检查每个ms的时间戳,并且plc周期为0.5 ms,您将获得1000个2000 plc周期滴答的值。
您假设运行时间为2秒,但实际上只有1秒。
2)
转换错误必须与matlab解释8字节的方式有关。
[在twincat中,您正在使用UNSIGNED long int ..,在matlab中?根据值前面的减号,必须将其解释为8字节有符号整数。