Re: MSCAN problem

> Hi everybody!
>
> I have a problem using the CAN-Bus interface of the HCS12 used in the
> MicroSquirt(tm) ECU we use on our Formula race car.
>
> Following the various data sheets I came up with the following code:
>
> void CanInit(void)
> {
>  /* Set up CAN communications */
> /* Enable CAN, set Init mode so can change registers */
> CANCTL1 |= 0x80;
> CANCTL0 |= 0x01;
>
> while(!(CANCTL1 & 0x01))
>   ;  // make sure in init mode
>
> /* Set Can enable, use IPBusclk (24 MHz),clear rest */
> CANCTL1 = 0xC0;
> /* Set timing for .5Mbits/ sec */
> CANBTR0 = 0xC2;  /* SJW=4,BR Prescaler= 3(24MHz CAN clk) */
> CANBTR1 = 0x1C;  /* Set time quanta: tseg2 =2,tseg1=13
>               (16 Tq total including sync seg (=1)) */
>
> CANIDAC &= ~0x30;   /* no filters */
>
> /* clear init mode */
> CANCTL0 &= 0xFE;
> /* wait for synch to bus */
> while(!(CANCTL0 & 0x10));
>
> /* no xmit yet */
> CANTIER = 0x00;
> /* clear RX flag to ready for CAN recv interrupt */
> CANRFLG = 0xC3;
> /* set CAN rcv full interrupt bit */
> CANRIER = 0x01;
> return;
> }
>
> void CanSend(CAN_message* msg)
> {
>    unsigned char txbuffer, i;
>    static unsigned char flag = 1;
>
>    if (!flag)
>      return;
>    flag = 0;
>
>    if (!CANTFLG)
>      return; // everything is more important than messages from the
> ECU, so just drop out if we cannot send
>
>    CANTBSEL = CANTFLG; // Select free buffer to use
>    txbuffer = CANTBSEL; // backup buffer
>
>    CAN_TB0_IDR0 = (unsigned char) msg->id >> 3; // higher 8 bits of id
>    CAN_TB0_IDR1 = (unsigned char) msg->id << 5; // lower 3 bits of id;
>    CAN_TB0_IDR1 &= ~(0x18); // Set to standard frames (IDE = 0)
>    CAN_TB0_IDR2 = 0;
>    CAN_TB0_IDR3 = 0;
>
>    for (i = 0; i < msg->length; i++) {
>      *(&CAN_TB0_DSR0 + i) = msg->data[i];
>    }
>
>    CAN_TB0_DLR = msg->length; // Set length
>    CAN_TB0_TBPR = 0; // priority
>
>    // Send message
>    CANTFLG = txbuffer;
> }
>
> However, when I send a single CAN message, MSCAN floods the CAN-Bus with
> messages (sending probably any us) and never stops. I checked on the
> osci and there is an ACK on the bus so I guess everything should be
> fine. Do I need to clear some buffer to make it stop sending messages?
>
> Thanks a lot for your help
>
> Johannes
>
>
> --
> Johannes Schmid
> High-Octane-Motorsports
> Teamleiter Elektronik
> johannes.schmid@...
> 0179 / 1674917
>
>
>
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