@MikeyH Hi Mike,
We found out that there were changes to systemd in Bookworm. On the clean image, there is a problem in DNS after installing DWM. We will adjust the DWM installation accordingly so that everything works on Bookworm and older distributions. We'll let you know when we have a solution.

Cheers,
Jan

@stepan-ozana
Thanks, that looks great! I'll modify the schema a little more to match the conventions of the other blocks and include it in the installation.

@stepan-ozana Thank you for your valuable insights! Your contribution to the collection of examples is greatly appreciated.

In the original 'EKF.zip' file mentioned at the beginning of this thread, the timing parameters were incorrectly set—my apologies for that. The best way to correct them is by changing the start and stop values in the task1 block to -1, as outlined in the manual. The log message 'CoreWarning GTimer: Period overtime.' appears whenever the task execution exceeds the maximum allowed time, which can be observed in Diagnostics. If this warning appears in the log while the Max time in Diagnostics does not exceed the allocated execution time (20 ms in the case of EKF.zip), it indicates an error.

We would greatly appreciate any further insights and improvements from your side. I had planned to simulate measurement noise similarly to your approach—by adding white noise to the measurement vector—but I hadn’t considered process noise. For your reference, I’m sharing the updated version of the example, which includes your reference model and the corrected timing parameters.

Linear system.zip

@stepan-ozana
First of all, thank you very much for adding the reference model. If you agree, I would like to add this model to the example on EKF, which is already part of the daily version of REXYGEN.

As for the timing. I think the problem may be in the Python block, which takes significantly longer to execute than the native blocks. Try looking in the Diagnostics and at the statistics on the execution of the task.

EKF - Linear System Model

This document describes the use of the Extended Kalman Filter (EKF) in the REXYGEN environment for state estimation of a linear system.

System Description

The system is described by the following differential equations:

\begin{aligned}
\frac{dx(t)}{dt} &= f(x(t), u(t)) + w(t),\\
y(t) &= h(x(t), u(t)) + v(t),\\
\hat{x}(t) &\sim \mathcal{N}(x, P),\\
w(t) &\sim \mathcal{N}(0, Q),\\
v(t) &\sim \mathcal{N}(0, R).
\end{aligned}

where:

• $ x(t) $ is the state vector,
• $ u(t) $ is the input vector,
• $ y(t) $ is the output vector,
• $ w(t) $ is the process noise,
• $ v(t) $ is the measurement noise,
• $ \hat{x}(t) $ is the estimated state vector,
• $ x $ is the mean (expected value),
• $ P $ is the state estimation covariance matrix,
• $ Q $ is the process noise covariance matrix,
• $ R $ is the measurement noise covariance matrix.

State Model of the System

The system dynamics are defined by the function $ f(x(t), u(t)) $:

f(x(t), u(t)) =
\begin{bmatrix}
\frac{dx_1(t)}{dt} \\
\frac{dx_2(t)}{dt} \\
\frac{dx_3(t)}{dt} \\
\frac{dx_4(t)}{dt}
\end{bmatrix}
=
\begin{bmatrix}
-x_1(t) + x_2(t) \\
-x_2(t) + x_3(t) \\
-x_3(t) + x_4(t) \\
-x_4(t) + u_1(t)
\end{bmatrix}.

Jacobian of the State Function

The Jacobian $ f(x, u) $ with respect to the state vector $ x $ is given as:

\frac{df(x(t), u(t))}{dx} =
\begin{bmatrix}
-1 & 1 & 0 & 0 \\
0 & -1 & 1 & 0 \\
0 & 0 & -1 & 1 \\
0 & 0 & 0 & -1
\end{bmatrix}

Output Measurements

The first set of output measurements (which, in this example, depend linearly on the state variables) for input EKF:nz = 1 is defined as:

y(t) = h_1(x(t), u(t)) = 
\begin{bmatrix}
x_1(t) \\
2 x_2(t) + 0.5 x_4(t)
\end{bmatrix},

with the corresponding Jacobian:

\frac{dh_1(x(t), u(t))}{dt} =
\begin{bmatrix}
1 & 0 & 0 & 0 \\
0 & 2 & 0 & 0.5 \\
\end{bmatrix}.

The second set of output measurements (for input EKF:nz = 2) is not used.

The system description is programmed into the REXLANG block.

This description serves as a basis for implementing the EKF in REXYGEN using the EKF function block. Further details can be found in the official documentation: EKF Block in REXYGEN.

@bech Hi,
here is a Markdown file describing the system, which is implemented in the REXLANG block. To view the equations correctly, copy the file's contents into an online editor, such as this one: https://markdownlivepreview.org

@bech Hi,

I'm sending an example of using EKF for a linear model. Please take a look at the code in the REXLANG block. Unfortunately, I don't have time to document the example in more detail right now. However, I should have time next week, so I'll send an improved version then.

Best regards,
Jan
EKF.zip

@mtomek Hello,
I'm really sorry—I somehow overlooked the fact that you were posting in this old thread. The "Warning 1 1" indicates that the buffer for serial communication between the Master and Slave devices is full:

#define WARNING_SERIAL 1
#define WARNING_SERIAL_BUFFER_FULL 1

Have you added any new data communication or changed the communication speed recently? I’d also like to point out that REXduino is a third-party project, and we don’t have direct control over it. I found the explanation for the warning directly in the source code here:
https://github.com/jaroslavs/REXduino/blob/master/REXduino_slave/REXduino_slave.ino

Cheers,
Jan

Hi @stepan-ozana,

The delay you're observing in Windows is likely due to process prioritization and interruption handling, which are less efficient and harder to control compared to a Linux-based system like Debian or Raspberry Pi OS. In Linux, you have better control over how processes are scheduled and managed, allowing the system to run more smoothly and minimizing the BUSY signal duration. Windows, on the other hand, tends to introduce more overhead when executing external processes, even if the script itself does nothing, due to the way it handles process management at the system level.

Additionally, our systems on Raspberry Pi use a real-time kernel, which further improves the timing and responsiveness of processes. That's why we recommend running time-critical processes on Debian-based systems.

Cheers,
Jan

@MikeyH Hi Mike,
The driver for controlling the GPIO pins on the Raspberry Pi 5 is finally available. I apologize for the delay. In the end, we had to develop an entirely new driver. This driver can also be used on older versions of Raspberry Pi, provided they are running Linux 5.10 or newer. The documentation for the driver is still being developed. However, everything should be described in the 0410_GPIO and 0411_PWM examples if you install the latest daily build of REXYGEN: https://download.rexcontrols.cz/partner/daily/

Cheers,
Jan

@Scoobsalamander Hi Kris,
I am sending the promised example from our developers: ethercat_basic_example.zip. A readme file with a brief description is included. Please let us know if anything is unclear.

Cheers,
Jan