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Gretchev
Associate II
Sep 13, 2025 4:45 PM UTC
Solved

Simple Classic CAN + FreeRTOS Demo simulating OBD and a vehicle

Building upon my previous post, "Bidirectional Serial Communication with ST-Link using FreeRTOS on NUCLEO Boards," this code demonstrates a Simulator component and an Application component operating on two separate NUCLEO-C092RC boards. Please note that this project is intended for educational use and is not designed as robust production code; some errors or omissions may remain that users will need to address. This initial demonstration should function as described when configured according to the provided instructions, and it may serve as a foundational template for future development and enhancements.

Val Gretchev

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    mƎALLEm
    mƎALLEmBest answer
    ST Technical Moderator
    Sep 17, 2025 9:58 AM UTC

    Hello @Gretchev and thank you for your contribution.

    I tested the two projects and they work well.
    If I summurize: the first CAN node, the "simulator" (as a car simulator), is diagnosed by the second CAN node, the "application" (simulating the OBD) which simulates the On-Board Diagnostics, diagnosing the car. NUCLEO-C092RC boards were used: one used to simulate a vehicle and the second one to simulate the OBD.

    This is the log obtained when sending different commends from the PC to the "application" over USART2 to request data from the vehicle (the simulator) over CAN.

    Welcome to STlink PC-to-MCU command interpreter
Starting default task
Starting UART command task
Starting CAN receive task
Starting CAN transmit task
A: toggle green LED
B: toggle blue LED
C: How now brown cow?
D: Same way black bull
R: Retrieve RPM
RX: 11b 0x7E8 41 0C RPM: 1500
S: Retrieve vehicle speed
RX: 11b 0x7E8 41 0D Speed: 60 km/h
T: Retrieve coolant temperature
RX: 11b 0x7E8 41 05 Coolant: 85B0 C

    r: to request the current engine RPM
    s: to request the current vehicle speed
    t: to request the current coolant temperature value

    Other commands, like a, b, c, d are miscs and used to toggle leds etc ..

    I will mark this comment as solution to give it more visibility for other users to help them to find efficiently this solution.

     

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    4 replies

    Ghofrane GSOURI
    Ghofrane GSOURI
    ST Technical Moderator
    Sep 15, 2025 8:56 AM UTC

    Hello @Gretchev 

    Thank you for sharing your project, "Bidirectional Serial Communication with ST-Link using FreeRTOS on NUCLEO Boards," on the ST Community. Your willingness to openly share your work and insights is truly appreciated.

    Thank you again for your contribution your efforts are making a positive impact and helping others learn and grow!

    THX

    Ghofrane

    To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
      mƎALLEm
      mƎALLEmBest answer
      ST Technical Moderator
      Sep 17, 2025 9:58 AM UTC

      Hello @Gretchev and thank you for your contribution.

      I tested the two projects and they work well.
      If I summurize: the first CAN node, the "simulator" (as a car simulator), is diagnosed by the second CAN node, the "application" (simulating the OBD) which simulates the On-Board Diagnostics, diagnosing the car. NUCLEO-C092RC boards were used: one used to simulate a vehicle and the second one to simulate the OBD.

      This is the log obtained when sending different commends from the PC to the "application" over USART2 to request data from the vehicle (the simulator) over CAN.

      Welcome to STlink PC-to-MCU command interpreter
Starting default task
Starting UART command task
Starting CAN receive task
Starting CAN transmit task
A: toggle green LED
B: toggle blue LED
C: How now brown cow?
D: Same way black bull
R: Retrieve RPM
RX: 11b 0x7E8 41 0C RPM: 1500
S: Retrieve vehicle speed
RX: 11b 0x7E8 41 0D Speed: 60 km/h
T: Retrieve coolant temperature
RX: 11b 0x7E8 41 05 Coolant: 85B0 C

      r: to request the current engine RPM
      s: to request the current vehicle speed
      t: to request the current coolant temperature value

      Other commands, like a, b, c, d are miscs and used to toggle leds etc ..

      I will mark this comment as solution to give it more visibility for other users to help them to find efficiently this solution.

       

      To give better visibility on the answered topics, please click "Best answer" on the reply which solved your issue or answered your question.
      GretchevAuthor
      Associate II
      Sep 17, 2025 1:49 PM UTC

      For the coolant temperature, I get:

      t
      T: Retrieve coolant temperature
      RX: 11b 0x7E8 41 05 Coolant: 85° C

      I guess not all PCs handle special characters the same way.

      Val

        GretchevAuthor
        Associate II
        Sep 17, 2025 2:17 PM UTC

        Although I haven’t tested this code in a vehicle, it should be able to retrieve those parameters from the car's OBD connector under the dash. All you need is an OBD cable. Dozens are available at Amazon.com. You only connect CAN High, CAN Low, and signal ground. Because the parameters retrieved from the OBD connector are dynamic, such as vehicle speed, the car must be in motion to obtain readings other than zero. For safety reasons, ensure a passenger is responsible for monitoring the laptop output at all times while the driver focuses on operating the vehicle.

        Val

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