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Where is the problem with SN65HVD232 ?

Metin KOC
Intellectual 610 points
Other Parts Discussed in Thread: LM3S8962

Hi everyone ;

I have a problem about canbus. I developed code at the LM3S8962 development board then i create my custom schematic. Now I can't get any data from LM3S5791. Do you think where is the problem ? 

My schematic is 

  • 0
    TI__Mastermind 20590 points

    Basic schematic seems okay, but you have to give a lot more information than just a basic schematic if you think it is with the transceivers which is this forum.  Did you terminate the CAN bus at the 2 ends (ie 120 ohm resistors at both ends).  Have you hooked up an oscilloscope and made sure data is actually being driven to the TXD (D) pins?  What do wave forms on  the bus look like?  Are you sure the s/w is configured correctly?

    -- Scott

  • 0 in reply to Scott Monroe
    Intellectual 610 points

    Yes , I terminated the bus with 2 120 resistor. And i measure the resistance like 60 ohm. Then i hooked up CAN L with oscilloscpe , it like that attachment picture.

    And software ;

    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
    GPIOPinTypeCAN(GPIO_PORTD_BASE, GPIO_PIN_0 | GPIO_PIN_1);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_CAN0);
    CANInit(CAN0_BASE);
    CANBitRateSet(CAN0_BASE, 8000000, 500000);
    CANEnable(CAN0_BASE);
    CANIntEnable(CAN0_BASE, CAN_INT_MASTER );
    IntEnable(INT_CAN0);

  • 0 in reply to Metin KOC
    TI__Mastermind 20590 points

    you really need to use CANH and CAN L as a pair to see if the differential output is being generated on the bus at the same time as monitoring TXD and RXD so you know if the bus matches the data being tramsitted.  If you think it is a s/w issue then please post questions about the s/w to the appropriated microprocessor forum.   Based on this scope shot it doesn't really help.  We really need to see what the bus is doing vs an active and valid TXD signal.  Keep in mind the CAN bus is a differential pair so you should see CANH = CANL = ~2.5V at recessive (logic 1) and CANH = ~3.2V and CANL = ~1.5V when dominant (logic 0).

    Is this the only device in a network, or are you inserting it with other operating CAN nodes? 

    -- Scott