CAN Library

mikroBasic PRO for dsPIC30/33 and PIC24 provides a library (driver) for working with the dsPIC30F CAN module.

The CAN is a very robust protocol that has error detection and signalization, self–checking and fault confinement. Faulty CAN data and remote frames are re-transmitted automatically, similar to the Ethernet.

Data transfer rates depend on distance. For example, 1 Mbit/s can be achieved at network lengths below 40m while 250 Kbit/s can be achieved at network lengths below 250m. The greater distance the lower maximum bitrate that can be achieved. The lowest bitrate defined by the standard is 200Kbit/s. Cables used are shielded twisted pairs.

CAN supports two message formats:

Standard format, with 11 identifier bits, and
Extended format, with 29 identifier bits

Important :

Consult the CAN standard about CAN bus termination resistance.
CAN library routines require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2.
Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CANxSetOperationMode

Prototype	sub procedure CANxSetOperationMode(dim mode, WAIT as word)
Description	Sets the CAN module to requested mode.
Parameters	`mode:` CAN module operation mode. Valid values: `CAN_OP_MODE` constants. See CAN_OP_MODE constants. `WAIT:` CAN mode switching verification request. If `WAIT == 0`, the call is non-blocking. The function does not verify if the CAN module is switched to requested mode or not. Caller must use CANxGetOperationMode to verify correct operation mode before performing mode specific operation. If `WAIT != 0`, the call is blocking – the function won’t “return” until the requested mode is set.
Returns	Nothing.
Requires	MCU with the CAN module. MCU must be connected to the CAN transceiver (MCP2551 or similar) which is connected to the CAN bus.
Example	' set the CAN1 module into configuration mode (wait inside CAN1SetOperationMode until this mode is set) CAN1SetOperationMode(_CAN_MODE_CONFIG, 0xFF)
Notes	CAN library routine require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2. Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CANxGetOperationMode

Prototype	sub function CANxGetOperationMode() as word
Description	The function returns current operation mode of the CAN module. See CAN_OP_MODE constants or device datasheet for operation mode codes.
Parameters	None.
Returns	Current operation mode.
Requires	MCU with the CAN module. MCU must be connected to the CAN transceiver (MCP2551 or similar) which is connected to the CAN bus.
Example	' check whether the CAN1 module is in Normal mode and if it is then do something. if (CAN1GetOperationMode() = _CAN_MODE_NORMAL) then ... end if
Notes	CAN library routine require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2. Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CANxInitialize

Prototype	sub procedure CANxInitialize(dim SJW, BRP, PHSEG1, PHSEG2, PROPSEG, CAN_CONFIG_FLAGS as word)
Description	Initializes the CAN module. The internal dsPIC30F CAN module is set to: Disable CAN capture Continue CAN operation in Idle mode Do not abort pending transmissions Fcan clock : 4*Tcy (Fosc) Baud rate is set according to given parameters CAN mode is set to Normal Filter and mask registers IDs are set to zero Filter and mask message frame type is set according to `CAN_CONFIG_FLAGS` value `SAM`, `SEG2PHTS`, `WAKFIL` and `DBEN` bits are set according to `CAN_CONFIG_FLAGS` value.
Parameters	`SJW` as defined in MCU's datasheet (CAN Module) `BRP` as defined in MCU's datasheet (CAN Module) `PHSEG1` as defined in MCU's datasheet (CAN Module) `PHSEG2` as defined in MCU's datasheet (CAN Module) `PROPSEG` as defined in MCU's datasheet (CAN Module) `CAN_CONFIG_FLAGS` is formed from predefined constants. See CAN_CONFIG_FLAGS constants.
Returns	Nothing.
Requires	MCU with the CAN module. MCU must be connected to the CAN transceiver (MCP2551 or similar) which is connected to the CAN bus.
Example	' initialize the CAN1 module with appropriate baud rate and message acceptance flags along with the sampling rules dim can_config_flags as word ... can_config_flags = _CAN_CONFIG_SAMPLE_THRICE and ' Form value to be used _CAN_CONFIG_PHSEG2_PRG_ON and ' with CAN1Initialize _CAN_CONFIG_STD_MSG and _CAN_CONFIG_DBL_BUFFER_ON and _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_LINE_FILTER_OFF CAN1Initialize(1,3,3,3,1,can_config_flags) ' initialize the CAN1 module
Notes	CAN mode NORMAL will be set on exit. CAN library routine require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2. Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CANxSetBaudRate

Prototype	sub procedure CANxSetBaudRate(dim SJW, BRP, PHSEG1, PHSEG2, PROPSEG, CAN_CONFIG_FLAGS as word)
Description	Sets CAN baud rate. Due to complexity of the CAN protocol, you can not simply force a bps value. Instead, use this function when CAN is in Config mode. Refer to datasheet for details. `SAM`, `SEG2PHTS` and `WAKFIL` bits are set according to `CAN_CONFIG_FLAGS` value. Refer to datasheet for details.
Parameters	`SJW` as defined in MCU's datasheet (CAN Module) `BRP` as defined in MCU's datasheet (CAN Module) `PHSEG1` as defined in MCU's datasheet (CAN Module) `PHSEG2` as defined in MCU's datasheet (CAN Module) `PROPSEG` as defined in MCU's datasheet (CAN Module) `CAN_CONFIG_FLAGS` is formed from predefined constants. See CAN_CONFIG_FLAGS constants.
Returns	Nothing.
Requires	MCU with the CAN module. MCU must be connected to the CAN transceiver (MCP2551 or similar) which is connected to the CAN bus. CAN must be in Config mode, otherwise the function will be ignored. See CANxSetOperationMode.
Example	' set required baud rate and sampling rules dim can_config_flags as word ... CAN1SetOperationMode(_CAN_MODE_CONFIG,0xFF) ' set CONFIGURATION mode (CAN1 module must be in config mode for baud rate settings) can_config_flags = _CAN_CONFIG_SAMPLE_THRICE and ' Form value to be used _CAN_CONFIG_PHSEG2_PRG_ON and ' with CAN1Initialize _CAN_CONFIG_STD_MSG and _CAN_CONFIG_DBL_BUFFER_ON and _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_LINE_FILTER_OFF CAN1SetBaudRate(1,3,3,3,1,can_config_flags) ' set the CAN1 module baud rate
Notes	CAN library routine require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2. Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CANxSetMask

Prototype	sub procedure CANxSetMask(dim CAN_MASK as word, dim val as longint, dim CAN_CONFIG_FLAGS as word)
Description	Function sets mask for advanced filtering of messages. Given `value` is bit adjusted to appropriate buffer mask registers.
Parameters	`CAN_MASK:` CAN module mask number. Valid values: `CAN_MASK` constants. See CAN_MASK constants. `val:` mask register value. This value is bit-adjusted to appropriate buffer mask registers `CAN_CONFIG_FLAGS:` selects type of message to filter. Valid values: `_CAN_CONFIG_ALL_VALID_MSG`, `_CAN_CONFIG_MATCH_MSG_TYPE & _CAN_CONFIG_STD_MSG`, `_CAN_CONFIG_MATCH_MSG_TYPE & _CAN_CONFIG_XTD_MSG`. See CAN_CONFIG_FLAGS constants.
Returns	Nothing.
Requires	MCU with the CAN module. MCU must be connected to the CAN transceiver (MCP2551 or similar) which is connected to the CAN bus. CAN must be in Config mode, otherwise the function will be ignored. See CANxSetOperationMode.
Example	' set appropriate filter mask and message type value CAN1SetOperationMode(_CAN_MODE_CONFIG,0xFF) ' set CONFIGURATION mode (CAN1 module must be in config mode for mask settings) ' Set all B1 mask bits to 1 (all filtered bits are relevant) ' Note that -1 is just a cheaper way to write 0xFFFFFFFF. ' Complement will do the trick and fill it up with ones. CAN1SetMask(_CAN_MASK_B1, -1, _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_XTD_MSG)
Notes	CAN library routine require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2. Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CANxSetFilter

Prototype	sub procedure CANxSetFilter(dim CAN_FILTER as word, dim val as longint, dim CAN_CONFIG_FLAGS as word)
Description	Function sets message filter. Given `value` is bit adjusted to appropriate buffer mask registers.
Parameters	`CAN_FILTER:` CAN module filter number. Valid values: `CAN_FILTER` constants. See CAN_FILTER constants. `val:` filter register value. This value is bit-adjusted to appropriate filter registers `CAN_CONFIG_FLAGS:` selects type of message to filter. Valid values: `_CAN_CONFIG_STD_MSG` and `_CAN_CONFIG_XTD_MSG`. See CAN_CONFIG_FLAGS constants.
Returns	Nothing.
Requires	MCU with the CAN module. MCU must be connected to the CAN transceiver (MCP2551 or similar) which is connected to the CAN bus. CAN must be in Config mode, otherwise the function will be ignored. See CANxSetOperationMode.
Example	' set appropriate filter value and message type CAN1SetOperationMode(_CAN_MODE_CONFIG,0xFF) ' set CONFIGURATION mode (CAN1 module must be in config mode for filter settings) ' Set id of filter B1_F1 to 3: CAN1SetFilter(_CAN_FILTER_B1_F1, 3, _CAN_CONFIG_XTD_MSG)
Notes	CAN library routine require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2. Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CANxRead

Prototype	sub function CANxRead(dim byref id as longint, dim byref data as byte[1], dim dataLen, CAN_RX_MSG_FLAGS as word) as word
Description	If at least one full Receive Buffer is found, it will be processed in the following way: Message ID is retrieved and stored to location pointed by `id` pointer Message data is retrieved and stored to array pointed by `data` pointer Message length is retrieved and stored to location pointed by `dataLen` pointer Message flags are retrieved and stored to location pointed by `CAN_RX_MSG_FLAGS` pointer
Parameters	`id:` message identifier address `data:` an array of bytes up to 8 bytes in length `dataLen:` data length address `CAN_RX_MSG_FLAGS:` message flags address. For message receive flags format refer to `CAN_RX_MSG_FLAGS` constants. See CAN_RX_MSG_FLAGS constants.
Returns	`0` if nothing is received `0xFFFF` if one of the Receive Buffers is full (message received)
Requires	MCU with the CAN module. MCU must be connected to the CAN transceiver (MCP2551 or similar) which is connected to the CAN bus. The CAN module must be in a mode in which receiving is possible. See CANxSetOperationMode.
Example	' check the CAN1 module for received messages. If any was received do something. dim msg_rcvd, rx_flags, data_len as word data as byte[8] msg_id as longint ... CAN1SetOperationMode(_CAN_MODE_NORMAL,0xFF) ' set NORMAL mode (CAN1 module must be in mode in which receive is possible) ... rx_flags = 0 ' clear message flags if (msg_rcvd = CAN1Read(msg_id, data, data_len, rx_flags)<>0) then ... end if
Notes	CAN library routine require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2. Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CANxWrite

Prototype	sub function CANxWrite(dim id as longint, dim byref data_ as byte[1], dim dataLen, CAN_TX_MSG_FLAGS as word) as word
Description	If at least one empty Transmit Buffer is found, the function sends message in the queue for transmission.
Parameters	`id:` CAN message identifier. Valid values: 11 or 29 bit values, depending on message type (standard or extended) `Data:` data to be sent `DataLen:` data length. Valid values: `0..8` `CAN_TX_MSG_FLAGS:` message flags. Valid values: `CAN_TX_MSG_FLAGS` constants. See CAN_TX_MSG_FLAGS constants.
Returns	`0` if all Transmit Buffers are busy `0xFFFF` if at least one Transmit Buffer is available
Requires	MCU with the CAN module. MCU must be connected to the CAN transceiver (MCP2551 or similar) which is connected to the CAN bus. The CAN module must be in mode in which transmission is possible. See CANxSetOperationMode.
Example	' send message extended CAN message with appropriate ID and data dim tx_flags as word data as byte[8] msg_id as longint ... CAN1SetOperationMode(_CAN_MODE_NORMAL,0xFF) ' set NORMAL mode (CAN1 must be in mode in which transmission is possible) tx_flags = _CAN_TX_PRIORITY_0 and _CAN_TX_XTD_FRAME and _CAN_TX_NO_RTR_FRAME ' set message flags CAN1Write(msg_id, data, 1, tx_flags)
Notes	CAN library routine require you to specify the module you want to use. To use the desired CAN module, simply change the letter x in the routine prototype for a number from 1 to 2. Number of CAN modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

CAN Constants

There is a number of constants predefined in CAN library. To be able to use the library effectively, you need to be familiar with these. You might want to check the example at the end of the chapter.

CAN_OP_MODE Constants

CAN_OP_MODE constants define CAN operation mode. Function CANxSetOperationMode expects one of these as its argument:

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const    _CAN_MODE_BITS    as word = $E0   ' Use this to access opmode  bits
         _CAN_MODE_NORMAL     as word = 0x00
         _CAN_MODE_DISABLE    as word = 0x01
         _CAN_MODE_LOOP       as word = 0x02
         _CAN_MODE_LISTEN     as word = 0x03
         _CAN_MODE_CONFIG     as word = 0x04
         _CAN_MODE_LISTEN_ALL as word = 0x07

CAN_CONFIG_FLAGS Constants

CAN_CONFIG_FLAGS constants define flags related to CAN module configuration. Functions CANxInitialize and CANxSetBaudRate expect one of these (or a bitwise combination) as their argument:

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const
    _CAN_CONFIG_DEFAULT         as word = 0xFF   ' 11111111

    _CAN_CONFIG_PHSEG2_PRG_BIT  as word = 0x01
    _CAN_CONFIG_PHSEG2_PRG_ON   as word = 0xFF   ' XXXXXXX1
    _CAN_CONFIG_PHSEG2_PRG_OFF  as word = 0xFE   ' XXXXXXX0

    _CAN_CONFIG_LINE_FILTER_BIT as word = 0x02
    _CAN_CONFIG_LINE_FILTER_ON  as word = 0xFF   ' XXXXXX1X
    _CAN_CONFIG_LINE_FILTER_OFF as word = 0xFD   ' XXXXXX0X

    _CAN_CONFIG_SAMPLE_BIT      as word = 0x04
    _CAN_CONFIG_SAMPLE_ONCE     as word = 0xFF   ' XXXXX1XX
    _CAN_CONFIG_SAMPLE_THRICE   as word = 0xFB   ' XXXXX0XX

    _CAN_CONFIG_MSG_TYPE_BIT    as word = 0x08
    _CAN_CONFIG_STD_MSG         as word = 0xFF   ' XXXX1XXX
    _CAN_CONFIG_XTD_MSG         as word = 0xF7   ' XXXX0XXX

    _CAN_CONFIG_DBL_BUFFER_BIT  as word = 0x10
    _CAN_CONFIG_DBL_BUFFER_ON   as word = 0xFF   ' XXX1XXXX
    _CAN_CONFIG_DBL_BUFFER_OFF  as word = 0xEF   ' XXX0XXXX

    _CAN_CONFIG_MATCH_TYPE_BIT  as word = 0x20
    _CAN_CONFIG_ALL_VALID_MSG   as word = 0xDF   ' XX0XXXXX
    _CAN_CONFIG_MATCH_MSG_TYPE  as word = 0xFF   ' XX1XXXXX

You may use bitwise and to form config byte out of these values. For example:

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init  = _CAN_CONFIG_SAMPLE_THRICE    and
        _CAN_CONFIG_PHSEG2_PRG_ON    and
        _CAN_CONFIG_STD_MSG          and
        _CAN_CONFIG_DBL_BUFFER_ON    and
        _CAN_CONFIG_VALID_XTD_MSG    and
        _CAN_CONFIG_LINE_FILTER_OFF
...
CAN1Initialize(1, 1, 3, 3, 1, init)   ' initialize CAN

CAN_TX_MSG_FLAGS Constants

CAN_TX_MSG_FLAGS are flags related to transmission of a CAN message:

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const
    _CAN_TX_PRIORITY_BITS as word = 0x03
    _CAN_TX_PRIORITY_0    as word = 0xFC   ' XXXXXX00
    _CAN_TX_PRIORITY_1    as word = 0xFD   ' XXXXXX01
    _CAN_TX_PRIORITY_2    as word = 0xFE   ' XXXXXX10
    _CAN_TX_PRIORITY_3    as word = 0xFF   ' XXXXXX11

    _CAN_TX_FRAME_BIT     as word = 0x08
    _CAN_TX_STD_FRAME     as word = 0xFF   ' XXXXX1XX
    _CAN_TX_XTD_FRAME     as word = 0xF7   ' XXXXX0XX

    _CAN_TX_RTR_BIT       as word = 0x40
    _CAN_TX_NO_RTR_FRAME  as word = 0xFF   ' X1XXXXXX
    _CAN_TX_RTR_FRAME     as word = 0xBF   ' X0XXXXXX

You may use bitwise and to adjust the appropriate flags. For example:

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' form value to be used with CANSendMessage:
send_config = _CAN_TX_PRIORITY_0     and
              _CAN_TX_XTD_FRAME      and
              _CAN_TX_NO_RTR_FRAME
...
CANSendMessage(id, data, 1, send_config)

CAN_RX_MSG_FLAGS Constants

CAN_RX_MSG_FLAGS are flags related to reception of CAN message. If a particular bit is set; corresponding meaning is TRUE or else it will be FALSE.

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 const
    _CAN_RX_FILTER_BITS  as word = 0x0007   ' Use this to access filter bits
    _CAN_RX_FILTER_1     as word = 0x00
    _CAN_RX_FILTER_2     as word = 0x01
    _CAN_RX_FILTER_3     as word = 0x02
    _CAN_RX_FILTER_4     as word = 0x03
    _CAN_RX_FILTER_5     as word = 0x04
    _CAN_RX_FILTER_6     as word = 0x05
    _CAN_RX_OVERFLOW     as word = 0x08  ' Set if Overflowed else cleared
    _CAN_RX_INVALID_MSG  as word = 0x10  ' Set if invalid else cleared
    _CAN_RX_XTD_FRAME    as word = 0x20  ' Set if XTD message else cleared
    _CAN_RX_RTR_FRAME    as word = 0x40  ' Set if RTR message else cleared
    _CAN_RX_DBL_BUFFERED as word = 0x80  ' Set if this message was hardware double-buffered

You may use bitwise and to adjust the appropriate flags. For example:

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if (MsgFlag and _CAN_RX_OVERFLOW) <> 0 then
  ...
  ' Receiver overflow has occurred.
  ' We have lost our previous message.
end if

CAN_MASK Constants

CAN_MASK constants define mask codes. Function CANxSetMask expects one of these as its argument:

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const
    _CAN_MASK_B1 as word = 0
    _CAN_MASK_B2 as word = 1

CAN_FILTER Constants

CAN_FILTER constants define filter codes. Function CANxSetFilter expects one of these as its argument:

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const
    _CAN_FILTER_B1_F1 as word = 0
    _CAN_FILTER_B1_F2 as word = 1
    _CAN_FILTER_B2_F1 as word = 2
    _CAN_FILTER_B2_F2 as word = 3
    _CAN_FILTER_B2_F3 as word = 4
    _CAN_FILTER_B2_F4 as word = 5

Library Example

The example demonstrates CAN protocol. The 1st node initiates the communication with the 2nd node by sending some data to its address. The 2nd node responds by sending back the data incremented by 1. The 1st node then does the same and sends incremented data back to the 2nd node, etc.

Code for the first CAN node:

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program CAN_1st

dim Can_Init_Flags, Can_Send_Flags, Can_Rcv_Flags, Rx_Data_Len as word
    RxTx_Data as byte[8]
    Rx_ID     as longint
    Msg_Rcvd  as word

const ID_1st as longint = 12111
const ID_2nd as longint = 3                           ' node IDs

main:

  ADPCFG = 0xFFFF
  PORTB  = 0
  TRISB  = 0

  Can_Init_Flags   = 0
  Can_Send_Flags   = 0
  Can_Rcv_Flags    = 0

  Can_Send_Flags   = _CAN_TX_PRIORITY_0 and           ' form value to be used
                     _CAN_TX_XTD_FRAME and            ' with CANSendMessage
                     _CAN_TX_NO_RTR_FRAME

  Can_Init_Flags   = _CAN_CONFIG_SAMPLE_THRICE and    ' form value to be used
                     _CAN_CONFIG_PHSEG2_PRG_ON and    ' with CANInitialize
                     _CAN_CONFIG_XTD_MSG and
                     _CAN_CONFIG_DBL_BUFFER_ON and
                     _CAN_CONFIG_MATCH_MSG_TYPE and
                     _CAN_CONFIG_LINE_FILTER_OFF

  RxTx_Data[0] = 9
  CAN1Initialize(1,3,3,3,1,Can_Init_Flags)            ' initialize CAN
  CAN1SetOperationMode(_CAN_MODE_CONFIG,0xFF)         ' set CONFIGURATION mode

  CAN1SetMask(_CAN_MASK_B1, -1, _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_XTD_MSG)  ' set all mask1 bits to ones
  CAN1SetMask(_CAN_MASK_B2, -1, _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_XTD_MSG)  ' set all mask2 bits to ones
  CAN1SetFilter(_CAN_FILTER_B2_F3,ID_2nd,_CAN_CONFIG_XTD_MSG) ' set id of filter B2_F3 to 2nd node ID

  CAN1SetOperationMode(_CAN_MODE_NORMAL,0xFF)                 ' set NORMAL mode


  CAN1Write(ID_1st, RxTx_Data, 1, Can_Send_Flags)

  while TRUE
    Msg_Rcvd = CAN1Read(Rx_ID , RxTx_Data , Rx_Data_Len, Can_Rcv_Flags)
    if ((Rx_ID = ID_2nd) and (Msg_Rcvd <> 0)) <> 0 then
      PORTB = RxTx_Data[0]                            ' output data at PORTB
      RxTx_Data[0] = RxTx_Data[0] + 1
      Delay_ms(10)
      CAN1Write(ID_1st, RxTx_Data, 1, Can_Send_Flags) ' send incremented data back
    end if
  wend
end.

Code for the second CAN node:

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program Can_2nd

dim Can_Init_Flags, Can_Send_Flags, Can_Rcv_Flags, Rx_Data_Len as word
    RxTx_Data as byte[8]
    Rx_ID     as longint
    Msg_Rcvd  as word

const ID_1st as longint = 12111
const ID_2nd as longint = 3                          ' node IDs

main:
  ADPCFG = 0xFFFF
  PORTB  = 0
  TRISB  = 0

  Can_Init_Flags = 0
  Can_Send_Flags = 0
  Can_Rcv_Flags  = 0

  Can_Send_Flags =  _CAN_TX_PRIORITY_0 and           ' form value to be used
                    _CAN_TX_XTD_FRAME and            ' with CANSendMessage
                    _CAN_TX_NO_RTR_FRAME

  Can_Init_Flags  =  _CAN_CONFIG_SAMPLE_THRICE and   ' form value to be used
                     _CAN_CONFIG_PHSEG2_PRG_ON and   ' with CANInitialize
                     _CAN_CONFIG_XTD_MSG and
                     _CAN_CONFIG_DBL_BUFFER_ON and
                     _CAN_CONFIG_MATCH_MSG_TYPE and
                     _CAN_CONFIG_LINE_FILTER_OFF

  CAN1Initialize(1,3,3,3,1,Can_Init_Flags)           ' initialize CAN
  CAN1SetOperationMode(_CAN_MODE_CONFIG,0xFF)        ' set CONFIGURATION mode

  CAN1SetMask(_CAN_MASK_B1, -1, _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_XTD_MSG)   ' set all mask1 bits to ones
  CAN1SetMask(_CAN_MASK_B2, -1, _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_XTD_MSG)   ' set all mask2 bits to ones
  CAN1SetFilter(_CAN_FILTER_B1_F1,ID_1st,_CAN_CONFIG_XTD_MSG)   ' set id of filter_B1_F1 to 1st node ID

  CAN1SetOperationMode(_CAN_MODE_NORMAL,0xFF)                   ' set NORMAL mode

  while TRUE
    Msg_Rcvd = CAN1Read(Rx_ID , RxTx_Data , Rx_Data_Len, Can_Rcv_Flags)
    if ((Rx_ID = ID_1st) and (Msg_Rcvd <> 0)) <> 0 then
      PORTB   = RxTx_Data[0]                                ' output data at portB
      RxTx_Data[0] = RxTx_Data[0] + 1
      CAN1Write(ID_2nd, RxTx_Data, 1, Can_Send_Flags)       ' send incremented data back
    end if
  wend
end.

HW Connection

Example of interfacing CAN transceiver with MCU and bus

Example of interfacing CAN transceiver with MCU and CAN bus

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