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LAUNCHXL-F28379D: CAN CODING

Karthikeya Sharma
Prodigy 70 points

Part Number: LAUNCHXL-F28379D

Hi,

I have a doubt in the code below. I am unable to understand the entry condition of the " if " block. I know that RXOK is the bit that has to be checked to confirm that the receiver has received the data with no errors. Isn't if (CAN_ES_RXOK) condition sufficient?

if(((HWREGH(CANA_BASE + CAN_O_ES) & CAN_ES_RXOK)) == CAN_ES_RXOK)
{
//
// Get the received message
//
CAN_readMessage(CANA_BASE, RX_MSG_OBJ_ID, rxMsgData);
GPIO_togglePin(65U);
rxMsgCount++;
}

Also, it would be helpful if you could define HWREGH and CAN_O_ES in short. I couldn't find it anywhere in the technical reference manual.

Thank you,

Karthikeya

  • 0
    TI__Guru* 95315 points
    Karthikeya Sharma said:
    Isn't if (CAN_ES_RXOK) condition sufficient?

    if (CAN_ES_RXOK) condition is not sufficient. You need to read the CANES register first. Only then the code can determine the status of the RXOK bit.

    Karthikeya Sharma said:
    it would be helpful if you could define HWREGH and CAN_O_ES in short.

    HWREGH is used to directly write/read registers.

    How to directly write/read registers:

    For accessing lower or upper 16-bits of a register, use HWREGH. (Have to add 2 to access upper 16-bits when dealing with byte peripherals such as CAN).

    HWREGH(ui32Base + CAN_O_IF1ARB) = 0x4321;     // Write 0x4321 to LOWER 16-bit

HWREGH(ui32Base + CAN_O_IF1ARB + 2) = 0x8765; // Write 0x8765 to UPPER 16-bit

    After executing the above 2 lines, CAN_0_IF1ARB should contain 0x87654321.

    For all 32-bit access, use HWREG_BP.

    HWREG_BP(ui32Base + CAN_O_IF1ARB) = 0x87654321;     // Write 0x87654321 to the 32 bits

    After executing the above line, CAN_0_IF1ARB should contain 0x87654321.

    CAN_O_ES refers to the CANES register.

  • 0 in reply to Hareesh Janakiraman
    Prodigy 70 points

    Thank you for responding sir.

    In this code snippet ((HWREGH (CANA_BASE + CAN_O_ES) & CAN_ES_RXOK)) == CAN_ES_RXOK, the lower 16 bits of the CANES register are read and a bitwise AND operation is performed on it. I did not understand what was going on here. Could you please explain it?

    Also, are CAN_O_ES and CAN_ES the same?

    Thank you

    Karthikeya

  • +1 in reply to Karthikeya Sharma
    TI__Guru* 95315 points
    Karthikeya Sharma said:
    In this code snippet ((HWREGH (CANA_BASE + CAN_O_ES) & CAN_ES_RXOK)) == CAN_ES_RXOK, the lower 16 bits of the CANES register are read and a bitwise AND operation is performed on it.

    Correct. It takes some effort to learn the coding style used in Driverlib, since multiple files are involved. 

    Karthikeya Sharma said:
    Also, are CAN_O_ES and CAN_ES the same?

    Already answered in the previous post. They are the same.