Hi Chirs,
I understand that you are attempting to read “modbus” registers at a frequency of 2 Hz using a timer object. However, you mentioned that the recorded sampling intervals vary and are not consistent with the desired sampling period of 0.5 seconds.
The MATLAB timer object is implemented using a combination of MATLAB's event-driven architecture and the underlying operating system's timer mechanisms. It internally utilizes the operating system's timer mechanisms to trigger timer events. However, the actual timing may be affected by factors such as system load, other tasks running concurrently, handling timer queuing conflicts, and the underlying hardware capabilities. Avoid using timer objects for real-time applications.
To address this issue and achieve more accurate timing, you can consider the following suggestions:
- Use the “tic” and “toc” functions: Instead of relying solely on the timer object's fixed rate, you can use the tic and toc functions to measure the elapsed time within each iteration. Internally, tic and toc do not rely on the operating system for timing. Instead, they use the high-resolution performance counter of the CPU to measure the elapsed time. It typically has a much higher resolution than the system clock used by the operating system. Here's an example:
desiredPeriod = 0.5; % desired sampling interval in seconds
numReadings = 10; % number of readings to take
tic;
for i = 1:numReadings
% Perform your modbus register reading here
% Calculate the elapsed time
elapsedTime = toc;
% Wait for the remaining time to achieve the desired period
remainingTime = desiredPeriod - elapsedTime;
if remainingTime > 0
pause(remainingTime);
end
% Reset the timer
tic;
end
2. Consider using the timer object's “StartDelay” property: You can set the “StartDelay” property of the timer object to delay the start of the timer execution, allowing for a more accurate initial timing. This can help compensate for any initialization or setup delays.
Please refer the following pages to learn more on the Limitations of “timer” object and Handling Timer Queuing Conflicts:
