CAN TX busy

Hello Siauhwa,

TX_OK means that the stream has been sent by the controller and a node on the n/w has ACK-ed the same. This would be after the transmission so the controller's transmitter is idle.

Regards
Amit

Hi Amit,

Please find my code below.
If I include delay(1) (1 ms delay) then the other node receives perfectly.
But, If I don't then the other node will only receive once. I guess its due to bus error as one or both of the nodes are not ready for another message.

If I set a breakpoint right after " status = CANStatusGet(CAN1_BASE, CAN_STS_CONTROL);" I got 0x00000008, which means "CAN_STATUS_TX_OK), eventhough I think the message has not sent completely at that moment.

Is there any common way to detect when the system is ready to send another message ?

Thank you
===


int CANSendStr (char *ptr_str_msg, unsigned int msg_len)
{
int index_string_msg;
while (*ptr_str_msg++)
{
msg.pui8MsgData = (string_msg + index_string_msg) ;
//delay(1); //delay of 1 ms
CANMessageSet(CAN1_BASE, 1, &msg, MSG_OBJ_TYPE_TX); // send as msg object 1
index_string_msg++;
}
}


void delay(unsigned int milliseconds) {
SysCtlDelay((sysClock / 3) * (milliseconds / 1000.0f));
}

// CAN interrupt handler
void CANIntHandler(void) {
unsigned long status = CANIntStatus(CAN1_BASE, CAN_INT_STS_CAUSE); // read interrupt status
if(status == CAN_INT_INTID_STATUS) { // controller status interrupt
status = CANStatusGet(CAN1_BASE, CAN_STS_CONTROL); // read back error bits, do something with them?
while ( status != CAN_STATUS_TXOK);
errFlag = 1;
} else if(status == 1) { // message object 1
CANIntClear(CAN1_BASE, 1); // clear interrupt
errFlag = 0; // clear any error flags
} else { // should never happen
UARTprintf("Unexpected CAN bus interrupt\n");
}
}

Hello Siauhwa,

Actually I have not used a polling mechanism in CAN, but relied on the Interrupt mechanism rather. I would gauge that if the Interrupt is not enabled then you have to read the CANINT register to be non-zero before reading the CANSTS to show an update and transmit the next message.

Regards
Amit

Hi,
Could you please give example code to do it in interrupt context.
Actually, I did it on interrupt context as well, as shown on my code above...

Hello Siauhwa

For TM4C123 there is an example already in TivaWare

C:\ti\TivaWare_C_Series-2.1.0.12573\examples\peripherals\can

In this code, the status from the Interrupt Handler as to a good transmission must be used to replace the SysCtlDelay in while(1) loop. For TM4C129 there is a similar code example that I had attached to a forum post almost 3-4 months back. You may have to search for the same in the forum.

Regards
Amit