Problem with RKS+CAN

Hello everyone,

I am currently trying to interface with an MB (Mercedes-Benz) control unit.
To achieve this, I work with the engine control unit (ECU), a digital oscilloscope (Hantek 6002BL), and RKS+CAN.

Unfortunately, when I connect RKS+CAN to the oscilloscope, I only get the following result.
Note: I desoldered the two 60 Ohm resistors (R1 & R2) from the RKS board because I read that they are mostly unnecessary for low-speed operation.

Furthermore, I can only send a maximum of 3 single messages using the KCANMonitor; after that, the tool stops responding; I then have to disconnect and reconnect the RKS in order to send more packets. Normal?

Thank you for the tips!
Best regards,
Johannes

P.S. Question: How can I encourage RKS to use Low-Speed CAN instead of always using High-Speed CAN?

Okay, I've managed to get a reasonably good signal for high-speed CAN again by adding an external termination resistor of approximately 150 ohms between CAN-H and CAN-L (see the image in the bottom right).

For me, the question remains why the KCANMonitor stops after three messages and doesn't continue (see the image on the left).

Sure, here are a few hints:

* The text is about a specific topic.
* The text is written in a formal style.
* The text is likely to be translated by a professional translator.

I hope these hints are helpful! Let me know if you have any other questions.

Thank you and best regards, - Johannes

Issue solved.

So, I learned two things:
1) The termination resistor is important (especially when working directly on a control unit without a vehicle).

"2) The correct bitrate must be known. Apparently, my car's main control unit (through sleep mode) consistently grounds the lines, resulting in no usable signal, and the RKS+CAN then (for unknown reasons) starts behaving erratically (namely, it simply shuts down after three packets). There may also be a logical and system-related explanation for this." For me, it meant: set the bitrate to 250 kbit, regularly send out the network manager package, and the MB control unit will become a chatterbox.

Topic can be closed.

Greetings - Johannes

Here are some more keywords for those interested in similar topics:
Mercedes, 213, CTRL, Push-to-talk, HMI, Head unit, Telematics, Wakeup, NM.

Thank you for the feedback .

Mercedes has not used a Low-Speed CAN bus for quite some time. And it's definitely not possible with 250 kbit/s; LowSpeed ends at 83.3 kbit/s.

The 213 typically uses a star termination, so you always need to terminate with 60 ohms.

The transceiver switches to low power (0 volts) when bus communication is no longer required.

If you simply send the highest NM value (0x57F) in the 1000ms cycle and set bit "0" in byte "0" to a logical 1, and set byte 1 to the NM address of your virtual NM node (0x7F), the control unit will remain in Repeat Message Mode.