Implementation of CAN Driver on LPC1768

[Laxmi_Gangal]

I am implementing a CAN driver for the LPC1768 microcontroller. During simulation there is no error, but while testing , I am encountering an ERRBIT : start of frame (SOF) in CAN  interrupt and capture status register(CANxICR) and in CAN1GSR TXERR: 0x7F TCS:0. 

My setup:

Software: keil u4

Microcontroller: LPC1768( ARM Cortex M3)

Baud rate: 500kbps

pin configuration: TD1(P0.1), RD1(P0.0)

CANxBTR register value: 0x00070004;

Init function:

void CAN_Init(uint8 CAN_Controller) {
volatile uint32 *powercontrol = (volatile uint32 *)PowerControl_Addr;
volatile uint32 *PCLKSEL0 = (volatile uint32 *)PCLKSEL0_Addr;
*PCLKSEL0 = 0x14000001;
if (CAN_Controller == 1) {
*powercontrol |= (0x01 << 13); // Power ON CAN1
} else if (CAN_Controller == 2) {
*powercontrol |= (0x01 << 14); // Power ON CAN2
}
}

baudrate snippet:

void CAN_Set_BaudRate(uint8 CAN_idx, uint32 baudrate_Kbps, uint32 PCLK_MHz, uint8 BRP, uint8 TSEG1, uint8 TSEG2) {
uint32 brp, btr_value;

btr_value = ((TSEG2 - 1) << 20) | ((TSEG1 - 1) << 16) | (0 << 14) | ((BRP-1)<<0);

if (CAN_idx == 1) {
CAN1->MOD = 1; // Enter Reset Mode
CAN1->BTR = btr_value; // Set BTR register
CAN1->MOD = 0; // ExIT
} else if (CAN_idx == 2) {
CAN2->MOD = 1; // Enter Reset Mode
CAN2->BTR = btr_value; // Set BTR register
CAN2->MOD = 0; // Exit Reset Mode
}
}

transmitter snippet:

void CAN_Transmit(uint8 CAN_Controller, CAN_msg *msg) {

if(CAN_Controller==1){

while (!(CAN1->SR & (0x01 << 2))); // Wait until TX buffer is empty

CAN1->TFI1 = ((msg->len &0xf)<< 16); // Set data length

CAN1->TID1 = msg->id; // Set identifier

CAN1->TDA1 = (msg->data[0]) | (msg->data[1] << | (msg->data[2] << 16) | (msg->data[3] << 24);

    CAN1->TDB1 = (msg->data[4]) | (msg->data[5] << | (msg->data[6] << 16) | (msg->data[7] << 24);

CAN1->CMR = (0x01 << 5) | (0x01 << 0); // Request transmission

CAN1->GSR=(1<<3);

}

else if(CAN_Controller==2){

while (!(CAN2->SR & (0x01 << 2))); // Wait until TX buffer is empty

CAN2->TFI1 = ((msg->len&0xf) << 16); // Set data length

CAN2->TID1 = msg->id; // Set identifier

CAN2->TDA1 = (msg->data[0]) | (msg->data[1] << | (msg->data[2] << 16) | (msg->data[3] << 24);

    CAN2->TDB1 = (msg->data[4]) | (msg->data[5] << | (msg->data[6] << 16) | (msg->data[7] << 24);

CAN2->CMR = (0x01 << 5) | (0x01 << 0); // Request transmission

CAN2->GSR=(1<<3);

}

}

receive snippet:

void CAN_Receive(uint8 CAN_Controller, CAN_msg *msg)

{

    if (CAN_Controller == 1)

    {

        while (!(CAN1->SR & (0x01 << 0))); // Check if a new message is received

        msg->len = (CAN1->RFS & 0x000F0000) >> 16; // Extract DLC

        msg->id =CAN1->RID;

/* Read first 4 data bytes */

*((uint8 *) &msg->data[0])= CAN1->RDA & 0x000000FF;

*((uint8 *) &msg->data[1])= (CAN1->RDA & 0x0000FF00)>>8;;

*((uint8 *) &msg->data[2])= (CAN1->RDA & 0x00FF0000)>>16;

*((uint8 *) &msg->data[3])= (CAN1->RDA & 0xFF000000)>>24;

/* Read second 4 data bytes */

*((uint8 *) &msg->data[4])= CAN1->RDB & 0x000000FF;

*((uint8 *) &msg->data[5])= (CAN1->RDB & 0x0000FF00)>>8;;

*((uint8 *) &msg->data[6])= (CAN1->RDB & 0x00FF0000)>>16;

*((uint8 *) &msg->data[7])= (CAN1->RDB & 0xFF000000)>>24;

        CAN1->CMR = (0x01 << 2); // Release receive buffer

    }

    else if (CAN_Controller == 2)

    {

        while (!(CAN2->GSR & (1 << 0))); // Check if a new message is received

        msg->len = (CAN2->RFS &  0x000F0000) >> 16; // Extract DLC

         msg->id = CAN2->RID;

*((uint8 *) &msg->data[0])= CAN2->RDA & 0x000000FF;

*((uint8 *) &msg->data[1])= (CAN2->RDA & 0x0000FF00)>>8;;

*((uint8 *) &msg->data[2])= (CAN2->RDA & 0x00FF0000)>>16;

*((uint8 *) &msg->data[3])= (CAN2->RDA & 0xFF000000)>>24;

/* Read second 4 data bytes */

*((uint8 *) &msg->data[4])= CAN2->RDB & 0x000000FF;

*((uint8 *) &msg->data[5])= (CAN2->RDB & 0x0000FF00)>>8;;

*((uint8 *) &msg->data[6])= (CAN2->RDB & 0x00FF0000)>>16;

*((uint8 *) &msg->data[7])= (CAN2->RDB & 0xFF000000)>>24;

        CAN2->CMR = (0x01 << 2); // Release receive buffer

    }

}

I have verified my pin configuration and CAN settings but cannot identify why the error is persisting.

Request:
Could anyone suggest what might be causing the ERRBIT: Start of Frame, TXERR:0x0F and how to resolve it? 

[Pablo_Ramos]

Hi @Laxmi_Gangal,

ERRBIT is when the CAN controller detects a bus error.

TXERR is the value of the Tx error counter, if a bus-off event occurs the TX error Counter is initialized to 127 (0x7F)

TCS: is the transmit complete status, when is on 0 it means that at least one requested transmission has not been successfully completed yet.

Could you help me checking the following?

What is the frame when reading it with a logic analyzer?

Are there other devices connected to the bus?

Also, you can take as reference the CAN demo based on lpc1769 under LPCopen.

LPCOpen Software for LPC17XX | NXP Semiconductors

[Laxmi_Gangal]

This is the frame it is reading.

I have not connected the receiver. I am reading the frame on port P0.1. Only Logic analyzer is connected to the LPC1768.

is both LPC1768 and LPC1769 is same or different?

[Pablo_Ramos]

Hi,

The main difference between LPC1768 and LPC1769 is the CPU frequency, however, you should be able to refer to LPC1769 in the CAN configuration.

Also, I recommend you to take a look to the following documentation regarding CAN

101: Controller Area Network (CAN) standard - NXP Community

If you connect the receiver do the frame stay the same?