Only three messages can be sent

I am using KCANMonitor, version RKS+CAN 2.70, build 403.

I have recorded some CAN messages and now I want to transmit them back onto the CAN bus.

To do this, I use "View" -> "Send and Replay". Next, use the "Import Frame List" function to read in the text file containing the recorded messages.

When I click the "Single" function, I see in the "Trace and Monitor" window that a message has been sent. Also, in the footer of the window, I see that the counter in the "Tx:" field increments by one. I can repeat this process as many times as I like, until I have used the "Single" function three times. Each subsequent click on the "Single" button has no effect.

I can only send three more messages after I disconnect and then reconnect to the interface.

Even when I use the "Send All" function, only three messages are sent.

Is this a known issue? I wanted to try an older version of KCANMonitor, but unfortunately, I can't find a suitable download link.

Can you help me?

Update from 08/12/2023 16:26: The problem only occurs when I have not connected the "RKS+CAN" cable to the vehicle's CAN bus, or when the vehicle has been turned off for a longer period of time (approximately 2 minutes). The problem occurs, for example, when the "RKS+CAN" cable is connected to the laptop via a USB A connector, but the OBD2 connector of the "RKS+CAN" cable is not connected to anything.

Why does the KCANMonitor program stop sending further messages after sending three messages? I don't understand that...

Hi,

There are no known issues related to this.
Please take a screenshot showing what you want to send.

The software doesn't really care whether a car is connected to the interface or not. It simply needs to be able to communicate with the interface. The interface is powered either via USB or the diagnostic port (diodes) when the interface is functioning correctly.

My suspicion leans more towards damage caused by a ground loop or some kind of standby function from the laptop or the USB device.

Best regards, Rainer.

Hello Rainer,

Thank you for taking the time to address my concern.

Quote:

Please take a screenshot showing what you want to send.

You will find the TXT file containing the recorded CAN bus messages in the attachment. I recorded this data by connecting the "RKS+CAN" interface to the drive's CAN bus (I used a multiplexer for this).

I also made a video for you so you can see how the problem manifests. The "RKS+CAN" interface was not connected to a CAN bus during the test.

In the video, it's clearly visible that the diode on the "RKS+CAN" interface initially lights up green, until the point where I use the "Connect CAN Interface" function. Subsequently, it starts blinking alternately red and orange. The interval pattern is:

long orange
long red
long orange
long red
long orange
short red

This pattern repeats until I click the "Single" button for the fourth time. With the fourth click on the "Single" button, you can observe that the diode remains orange, the Tx counter does not increment by 1, and a fourth message does not appear in the "Trace and Monitor" window.

I also tested the interface with a friend's laptop. However, even with my friend's laptop, I can only send three messages. So, it's the same behavior as with my laptop.

Do you have any suggestions for settings I could change to fix the problem?

Hi,

The LEDs indicate that transmission errors are occurring on the CAN bus. Nothing is being sent, and nothing is being received anywhere.

Quote:

Do you have any idea which setting I can change to fix the problem?

Connect/configure the CAN in such a way that the bus functions.

What you're doing is like trying to use a landline phone without a phone cable and then being surprised that it shows an "error."

Best regards, Rainer.

Hi Rainer,

Quote:

What you're doing is like having a landline phone that allows you to select a number without a phone cable, and then being surprised that it displays an "error"...

Thank you for your feedback. Therefore, my experimental setup, in which I do not connect the "RKS+CAN" interface anywhere, is not valid. I was not aware of this. Therefore, I wonder what is the minimum required to ensure the validity of the experimental setup.


Would the following experimental setup be valid?

Connect a
• 2-meter long cable to the CAN High connector of the multiplexer (connect to the blue fin connector).
  
  Connect a
• 2-meter long cable to the CAN High connector of the multiplexer (connect to the blue fin connector).
  
  
• Connect both ends of the two CAN bus cables with a 120 Ohm resistor.
  
  Connect the
• Interface "RKS+CAN" to the blue female OBD2 connector of the multiplexer.
  
  
• Messages that are stored in the file "Test CAN Bus Messages.txt" should be replayed using the "Send and Replay" function.
  

Do you think this experimental setup will be successful?

Hi.

To enable communication on a CAN bus, at least two nodes are required. Since a sent message must be acknowledged by the receiver via the ACK bit, the sending controller raises an error flag if the message was not properly acknowledged.

In addition, the bus termination with 120 ohms is important. However, in most cases, appropriate electronics are already installed at the relevant nodes when you are using control units from the car.

Sure, here's the translation:

"LG" translates to "Best regards" or "Sincerely" in English.

Quote:

Since a sent message must be acknowledged by a receiver through the ACK bit, the sending controller raises an error flag if the message was not properly ACKed.

Ah, I didn't know about the ACK bit (I still know a lot about the CAN bus ).

I'm going to set up another experiment and will get back to you with the results.

Excellent description of the CAN physical layer.
https://www.ti.com/lit/an/slla270/slla270.pdf

Quote:

I thank you .https://www.ti.com/lit/an/slla270/slla270.pdf{MARKER}