Re: MSCAN problem

> Edward
>
> ----- Original Message -----
> From: "Johannes Schmid" <johannes.schmid@...>
> To: <68HC12@...>
> Sent: Wednesday, May 06, 2009 21:33
> Subject: [68HC12] 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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