[PIC] Request For CAN information.

[Zong Zai]

Hi,

Good morning every buddy.

I had try to touch about CAN communication for PIC32. I'm unfamiliar to CAN. Before this i had using rs232 , i2c and rs485 for communication, but now wan to use CAN. It is difference with i2c, for example i2c transmit data bu using the word Masterputs , masterwrite , slaveput , slaveget and receive, but for CAN case i didn't get the certain word to transmit or receive. So any buddy can help to explain for me??
Thank you!

 

[Zong Zai]

Hi horace,

Thanks for your response, as you mean that if i set my microcontroller will be take action when receive the certain command, right?
I wan to use CAN to communicate from a PIC32 to another PIC32.
I show you my wiring.
I wan to use CAN1 transmit command to CAN2 and CAN2 transmit to CAN1.
Any idea?

void CAN1Init(void)
{

	CAN_BIT_CONFIG canBitConfig;
	CANEnableModule(CAN1,TRUE);

	CANSetOperatingMode(CAN1, CAN_CONFIGURATION);
	while(CANGetOperatingMode(CAN1) != CAN_CONFIGURATION);

	canBitConfig.phaseSeg2Tq            = CAN_BIT_3TQ;
	canBitConfig.phaseSeg1Tq            = CAN_BIT_3TQ;
	canBitConfig.propagationSegTq       = CAN_BIT_3TQ;
	canBitConfig.phaseSeg2TimeSelect    = TRUE;
	canBitConfig.sample3Time            = TRUE;
        canBitConfig.syncJumpWidth          = CAN_BIT_2TQ;

    CANSetSpeed(CAN1,&canBitConfig,SYS_FREQ,500000);
    CANAssignMemoryBuffer(CAN1,CAN1MessageFifoArea,(2 * 8 * 16));
    CANConfigureChannelForTx(CAN1, CAN_CHANNEL0, 8, CAN_TX_RTR_DISABLED, CAN_LOW_MEDIUM_PRIORITY);
    CANConfigureChannelForRx(CAN1, CAN_CHANNEL1, 8, CAN_RX_FULL_RECEIVE);

    CANConfigureFilter      (CAN1, CAN_FILTER0, 0x201, CAN_SID);
    CANConfigureFilterMask  (CAN1, CAN_FILTER_MASK0, 0xFFF, CAN_SID, CAN_FILTER_MASK_IDE_TYPE);
    CANLinkFilterToChannel  (CAN1, CAN_FILTER0, CAN_FILTER_MASK0, CAN_CHANNEL1);
    CANEnableFilter         (CAN1, CAN_FILTER0, TRUE);

    CANEnableChannelEvent(CAN1, CAN_CHANNEL1, CAN_RX_CHANNEL_NOT_EMPTY, TRUE);
    CANEnableModuleEvent (CAN1, CAN_RX_EVENT, TRUE);
    INTSetVectorPriority(INT_CAN_1_VECTOR, INT_PRIORITY_LEVEL_4);
    INTSetVectorSubPriority(INT_CAN_1_VECTOR,  INT_SUB_PRIORITY_LEVEL_0);
    INTEnable(INT_CAN1, INT_ENABLED);
    CANSetOperatingMode(CAN1, CAN_NORMAL_OPERATION);
    while(CANGetOperatingMode(CAN1) != CAN_NORMAL_OPERATION);

}
void CAN2Init(void)
{
    CAN_BIT_CONFIG canBitConfig;
	CANEnableModule(CAN2,TRUE);

	CANSetOperatingMode(CAN2, CAN_CONFIGURATION);
	while(CANGetOperatingMode(CAN2) != CAN_CONFIGURATION);
	canBitConfig.phaseSeg2Tq            = CAN_BIT_4TQ;
	canBitConfig.phaseSeg1Tq            = CAN_BIT_4TQ;
	canBitConfig.propagationSegTq       = CAN_BIT_4TQ;
	canBitConfig.phaseSeg2TimeSelect    = TRUE;
	canBitConfig.sample3Time            = TRUE;
    canBitConfig.syncJumpWidth          = CAN_BIT_3TQ;

    CANSetSpeed(CAN2, &canBitConfig, SYS_FREQ, 500000);
    CANAssignMemoryBuffer(CAN2,CAN2MessageFifoArea,2 * 8 * 16);
    CANConfigureChannelForTx(CAN2,CAN_CHANNEL2,8,CAN_TX_RTR_ENABLED,CAN_LOW_MEDIUM_PRIORITY);
    CANConfigureChannelForRx(CAN2, CAN_CHANNEL3, 8, CAN_RX_FULL_RECEIVE);

    CANConfigureFilter      (CAN2, CAN_FILTER0, 0x202, CAN_SID);
    CANConfigureFilterMask  (CAN2, CAN_FILTER_MASK0, 0xFFF, CAN_SID, CAN_FILTER_MASK_IDE_TYPE);
    CANLinkFilterToChannel  (CAN2, CAN_FILTER0, CAN_FILTER_MASK0, CAN_CHANNEL0);
    CANEnableFilter         (CAN2, CAN_FILTER0, TRUE);


    CANEnableChannelEvent(CAN2, CAN_CHANNEL3, CAN_RX_CHANNEL_NOT_EMPTY, TRUE);
    CANEnableModuleEvent (CAN2, CAN_RX_EVENT, TRUE);
    INTSetVectorPriority(INT_CAN_2_VECTOR, INT_PRIORITY_LEVEL_4);
    INTSetVectorSubPriority(INT_CAN_2_VECTOR,  INT_SUB_PRIORITY_LEVEL_0);
    INTEnable(INT_CAN2, INT_ENABLED);

	CANSetOperatingMode(CAN2, CAN_NORMAL_OPERATION);
	while(CANGetOperatingMode(CAN2) != CAN_NORMAL_OPERATION);

}
void CAN1TxSendRTRMsg(void)
{
	CANTxMessageBuffer * message;

	message = CANGetTxMessageBuffer(CAN1,CAN_CHANNEL0);
        //message = CANTxMessageBuffer(CAN1,CAN_CHANNEL0);

	message->messageWord[0] = 1;
	message->messageWord[1] = 1;
	message->messageWord[2] = 1;
	message->messageWord[3] = 1;

	message->msgSID.SID= 0x202;		/* Send message to CAN2.				*/
	message->msgEID.IDE = 0;			/* IDE = 0 means Standard ID message.	*/
	message->msgEID.RTR = 1;			/* Set the RTR bit.	*/
	message->msgEID.DLC = 1;			/* No data payload for RTR messages.	*/
        message->data[0]= 0x03;	/* This is the payload.					*/
        message->data[1]= 0x33;
        message->data[2]= 0x33;
        message->data[3]= 0x33;
        message->data[4]= 0x33;
        message->data[5]= 0x33;
        message->data[6]= 0x33;
        message->data[7]= 0x33;

    CANUpdateChannel(CAN1,CAN_CHANNEL0);

    CANFlushTxChannel(CAN1,CAN_CHANNEL0);

}
void CAN2RxMsgProcess(void)
{
	CANRxMessageBuffer * message;
	message = (CANRxMessageBuffer *)CANGetRxMessage(CAN2,CAN_CHANNEL3);
	if(message->data[0] == '1')
	{
          //take action
	}
	else
	{
            //take action
	}


    CANUpdateChannel(CAN2, CAN_CHANNEL3);
	CANEnableChannelEvent(CAN2, CAN_CHANNEL3, CAN_RX_CHANNEL_NOT_EMPTY, TRUE);
}

 

[horace1]

Canbus is not a master/slave system like I2C or SPI or a point to point network like a TCP/P network. In particular the nodes do not have an address. The frames carry a message ID, all the nodes on the network can examine the frame and if the message is relevant read the data. For example, in a vechicle a message sent to switch on the running lights may be read by a number of nodes which control lighting system.
Messages are read and transmitted using commands such as

CANGetMsg( int Channel, UINT32* pIdentifier, int *RTR, UINT8* Msg, UINT8* pMsgSize );
BOOL CANSendMsgExtended( int Channel, UINT32 Identifier, UINT8* Msg, UINT8 MsgSize );

in practice you chose a communications system to suit the application - what do you want to do?

- - - Updated - - -

have a look at
**broken link removed**

there is a PIC32 CAN to Ethernet bridge demo
https://ww1.microchip.com/downloads/en/DeviceDoc/CAN to Ethernet Bridge_070811.exe

 

[FvM]

I want to use CAN1 transmit command to CAN2 and CAN2 transmit to CAN1.

That's surely possible.

Any idea?

Do you want Edaboard members to write your test code?

I see that you copied a Microchip CAN example, and it would be much better readable if you had kept the verbose comments of the original code! I wonder if you are asking anything that isn't already explained in the comments.

 

[horace1]

it should work - have you termination resistors on the CAN lines?


what happens? using an oscilloscope can you see signals on the CAN lines?
do you have a UART connection to a PC so you can use printf() to see what is happening?

I find a CAN-USB device is useful for debugging CAN networks, e.g.
http://www.can232.com/
**broken link removed**

 

[Zong Zai]

Hi FvM,

I had copied the CAN example code from microchip, but i confused about the code. How can i send the command or string? Can show me?

void CAN2RxMsgProcess(void)
{
	CANRxMessageBuffer * message;
	message = (CANRxMessageBuffer *)CANGetRxMessage(CAN2,CAN_CHANNEL3);
	if(message->data[0] == '1')
	{
          //take action
	}
	else
	{
            //take action
	}


    CANUpdateChannel(CAN2, CAN_CHANNEL3);
	CANEnableChannelEvent(CAN2, CAN_CHANNEL3, CAN_RX_CHANNEL_NOT_EMPTY, TRUE);
}

The data i received message->data[0] is 0. Is it the data i receive is correct?

- - - updated - -

Hi horace,

i had connect the resistor 120R between CAN_L and CAN_H.
When i observe the signal using the oscilloscope, the signal for CAN_L and CAN_H is high.
I had use UART for observe, as the code i write above, the message->data[0] i receive is 0.

Thank you^^

 

[horace1]

Hi FvM,

I had copied the CAN example code from microchip, but i confused about the code. How can i send the command or string?
The data i received message->data[0] is 0. Is it the data i receive is correct?

looking at an earlier post your were setting the RTR bit and an RTR frame normally carries no message
e.g. I have sent two messages with ID 0xAAA first one normal frame with data )x1234567800000000 the second is an RTR frame