Posted on January 12, 2005 at 08:48Hi All
I am having trouble getting the CAN module to work.
By using the following code to initialise the module in loop back mode I can see transmitted messages correctly using a can bus monitor.
Also a receive interrupt gets generated each time I transmit a message.
void Can_Init(void)
{
GPIO_Config(GPIO1,(1<
GPIO_Config(GPIO1,(1<
CAN->CR = CAN_CR_CCE | CAN_CR_INIT | CAN_CR_TEST;
CAN->TESTR=0x0010; // set loopback mode to test
CAN->SR = 0; // reset the status
CAN->BRPR = 0;
CAN->BTR=0x34d7; // 100kbits @ 24Mhz clk
CAN_InvalidateAllMsgObj();
SetMessageObjects(); // set message object 1 to transmit and 2- 32 as receive fifo
CAN->CR = CAN_CR_IE | CAN_CR_TEST ;
}
Because it works fine in loop back mode I assume I have the message objects setup correctly.
Now when I set
CAN->TESTR=0x0000;
and
CAN->CR = CAN_CR_IE;
at the end of Can_Init(). After I do this
I no longer see CAN messages externally.
I dont get a receive interrupt if I send CAN messages to the board.
I dont get a ''message transmitted ok'' in the CAN_SR register
The CAN_TRnR register has the correct bit set to indicate I have requested a transmit.
The CAN_NDnR register has the corresponding bit cleared, even though I set it in the transmit. Is it cleared by the CAN module ?
The CAN_MVnR register has the correct bit to indicate the message object is valid.
I am confused as to why I can get CAN messages in test mode with loop back enabled but as soon as I
come out of test mode nothing appears to work.
Also if I stay in test mode but dont enable loop back (CAN_TESTR = 0) I still get no CAN externally even though from the data sheet I would expect some as bits 5 & 6 indicate the CAN_TRX pin is controlled by the CAN moudle.
I have spent a day trying to get this to work and as far as I can see I am not doing anything wrong.
thanks for any help
Ben,
