CAN Library

mikroBasic PRO for PIC32 provides a library (driver) for working with the PIC32 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 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_Init_Flags as word ... Can_Init_Flags = _CAN_CONFIG_SAMPLE_THRICE and ' Form value to be used _CAN_CONFIG_PHSEG2_PRG_ON and ' with CAN1Initialize _CAN_CONFIG_XTD_MSG and _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_LINE_FILTER_OFF CAN1Initialize(1,3,3,3,1,Can_Init_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.

CANxAssignBuffer

Prototype	sub procedure CANxAssignBuffer(dim buffer as ^byte)
Description	Assigns FIFO buffer for the CAN module .
Parameters	`buffer:` pointer to a space in the RAM where the CAN message FIFO buffers will be stored.
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	dim Buffers as byte[2816] absolute 0xA0000000 CAN1AssignBuffer(@Buffers)
Notes	CAN module can have up to 32 FIFO buffers, each having up to 32 messages. Transmit message size is 16 bytes long, while the receive message size may be 16 bytes (for full receive message mode) or 8 bytes for data-only message receive. 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.

CANxConfigureFIFO

Prototype	sub procedure CANxConfigureFIFO(dim num as byte, dim size as byte, dim flags as word)
Description	Configures CAN FIFO buffers.
Parameters	`num:` FIFO buffer number. `size:` Size of the FIFO buffer (in messages). `flags:` parameter is formed from the predefined constants. See CAN_RX_MSG_FLAGS, CAN_TX_MSG_FLAGS and CAN_FIFO 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	' configure RX FIFO buffer CAN1ConfigureFIFO(_CAN_BUFFER_0, 8, _CAN_FIFO_RX and _CAN_FULL_MESSAGE) ' configure TX FIFO buffer CAN1ConfigureFIFO(_CAN_BUFFER_1, 8, _CAN_FIFO_TX and _CAN_TX_NO_RTR_FRAME and _CAN_TX_PRIORITY_3)
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 CAN1SetBaudRate _CAN_CONFIG_STD_MSG 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	The function configures appropriate mask for advanced message filtering.
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) CAN1SetMask(_CAN_MASK_0, -1, _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_XTD_MSG) ' set all mask1 bits to ones
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.

CANxFilterEnable

Prototype	sub procedure CANxFilterEnable(dim CAN_FILTER as byte)
Description	The function enables appropriate receive message filters.
Parameters	`CAN_FILTER:` filter enable selection parameter. Each bit corresponds to appropriate filter. By setting bit the corresponding filter will be enabled.
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	' Filters 0, 4, 8, 12 are to be enabled: CAN1FilterEnable(0x1111)
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.

CANxFilterDisable

Prototype	sub procedure CANxFilterDisable(dim CAN_FILTER as byte)
Description	The function disables appropriate receive message filters.
Parameters	`CAN_FILTER:` filter disable selection parameter. Each bit corresponds to appropriate filter. By setting bit the corresponding filter will be disabled.
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	' Filters 0, 4, 8, 12 are to be disabled: CAN1FilterDisable(0x1111)
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 longword, dim CAN_FILTER_MASK, CAN_FILTER_RXBUFF, 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_FILTER_MASK:` selects type of message to filter. See CAN_MASK constants. `CAN_FILTER_RXBUFF:` selects type of message to filter. See CAN_BUFFER constants. `CAN_CONFIG_FLAGS:` selects type of message to filter. Valid values: 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) CAN1SetFilter(_CAN_FILTER_31, ID_1st, _CAN_MASK_3, _CAN_BUFFER_0, _CAN_CONFIG_XTD_MSG); ' set id of filter_B1_F1 to 1st node ID
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.

CANxReadBuffer

Prototype	sub function CANxReadBuffer(dim byref id as longword, dim byref data_ as byte[8], dim buffer as byte, dim byref dataLen as word, dim byref CAN_RX_MSG_FLAGS as word) as word
Description	If a 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_`. Message receive buffer is determined by the `buffer` parameter. 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. `buffer:` receive buffer. `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	if (msg_rcvd = CAN1ReadBuffer(msg_id, data, _CAN_BUFFER_0, 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.

CANxRead

Prototype	sub function CANxRead(dim byref id as longword, dim byref Data_ as byte[8], 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.

CANxWriteBuffer

Prototype	sub function CANxWriteBuffer(dim id as longword, dim byref Data_ as byte[8], dim buffer as byte, dim DataLen, CAN_TX_MSG_FLAGS as word) as word
Description	If a 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 Message transmit buffer is determined by the `buffer` parameter. `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 CAN1WriteBuffer(msg_id, data, _CAN_BUFFER_0, 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.

CANxWrite

Prototype	sub function CANxWrite(dim id as longword, dim byref Data_ as byte[8], 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_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_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 = 0x0003
    _CAN_TX_PRIORITY_0    as word = 0xFFFC   ' XXXXXX00
    _CAN_TX_PRIORITY_1    as word = 0xFFFD   ' XXXXXX01
    _CAN_TX_PRIORITY_2    as word = 0xFFFE   ' XXXXXX10
    _CAN_TX_PRIORITY_3    as word = 0xFFFF   ' XXXXXX11

    _CAN_TX_FRAME_BIT     as word = 0x0008
    _CAN_TX_STD_FRAME     as word = 0xFFFF   ' XXXXX1XX
    _CAN_TX_XTD_FRAME     as word = 0xFFF7   ' XXXXX0XX

    _CAN_TX_RTR_BIT       as word = 0x0040
    _CAN_TX_NO_RTR_FRAME  as word = 0xFFFF   ' X1XXXXXX
    _CAN_TX_RTR_FRAME     as word = 0xFFBF   ' 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 = 0x001F   ' Use this to access filter bits
    _CAN_RX_OVERFLOW     as word = 0x0020  ' Set if Overflowed else cleared
    _CAN_RX_INVALID_MSG  as word = 0x0040  ' Set if invalid else cleared
    _CAN_RX_XTD_FRAME    as word = 0x0080  ' Set if XTD message else cleared
    _CAN_RX_RTR_FRAME    as word = 0x0100  ' Set if RTR message else cleared
    _CAN_RX_DATA_ONLY    as word = 0x0200  ' 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_BUFFER Constants

CAN_BUFFER constants define CAN buffers. Function CANxAssignBuffer expects one of these as its argument:

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const
    _CAN_BUFFER_0  as word = 0
    _CAN_BUFFER_1  as word = 1
    _CAN_BUFFER_2  as word = 2
    _CAN_BUFFER_3  as word = 3
    _CAN_BUFFER_4  as word = 4
    _CAN_BUFFER_5  as word = 5
    _CAN_BUFFER_6  as word = 5
    _CAN_BUFFER_7  as word = 7
    _CAN_BUFFER_8  as word = 8
    _CAN_BUFFER_9  as word = 9
    _CAN_BUFFER_10 as word = 10
    _CAN_BUFFER_11 as word = 11
    _CAN_BUFFER_12 as word = 12
    _CAN_BUFFER_13 as word = 13
    _CAN_BUFFER_14 as word = 14
    _CAN_BUFFER_15 as word = 15
    _CAN_BUFFER_16 as word = 16
    _CAN_BUFFER_17 as word = 17
    _CAN_BUFFER_18 as word = 18
    _CAN_BUFFER_19 as word = 19
    _CAN_BUFFER_20 as word = 20
    _CAN_BUFFER_21 as word = 21
    _CAN_BUFFER_22 as word = 22
    _CAN_BUFFER_23 as word = 23
    _CAN_BUFFER_24 as word = 24
    _CAN_BUFFER_25 as word = 25
    _CAN_BUFFER_26 as word = 26
    _CAN_BUFFER_27 as word = 27
    _CAN_BUFFER_28 as word = 28
    _CAN_BUFFER_29 as word = 29
    _CAN_BUFFER_30 as word = 30
    _CAN_BUFFER_31 as word = 31

CAN_FIFO Constants

CAN_FIFO constants define FIFO constants. Function CANxConfigureFIFO expects one of these as its argument:

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const
    _CAN_FIFO_TXEN_BIT as word = 0x0080
    _CAN_FIFO_TX as word = 0xFF7F
    _CAN_FIFO_RX as word = 0xFFFF

    _CAN_FIFO_DONLY_BIT as word = 0x1000
    _CAN_DATA_ONLY as word = 0xEFFF
    _CAN_FULL_MESSAGE as word = 0xFFFF

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_B0 as word = 0
    _CAN_MASK_B1 as word = 1
    _CAN_MASK_B2 as word = 2
    _CAN_MASK_B3 as word = 3

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_0  as word = 0
    _CAN_FILTER_1  as word = 1
    _CAN_FILTER_2  as word = 2
    _CAN_FILTER_3  as word = 3
    _CAN_FILTER_4  as word = 4
    _CAN_FILTER_5  as word = 5
    _CAN_FILTER_6  as word = 5
    _CAN_FILTER_7  as word = 7
    _CAN_FILTER_8  as word = 8
    _CAN_FILTER_9  as word = 9
    _CAN_FILTER_10 as word = 10
    _CAN_FILTER_11 as word = 11
    _CAN_FILTER_12 as word = 12
    _CAN_FILTER_13 as word = 13
    _CAN_FILTER_14 as word = 14
    _CAN_FILTER_15 as word = 15
    _CAN_FILTER_16 as word = 16
    _CAN_FILTER_17 as word = 17
    _CAN_FILTER_18 as word = 18
    _CAN_FILTER_19 as word = 19
    _CAN_FILTER_20 as word = 20
    _CAN_FILTER_21 as word = 21
    _CAN_FILTER_22 as word = 22
    _CAN_FILTER_23 as word = 23
    _CAN_FILTER_24 as word = 24
    _CAN_FILTER_25 as word = 25
    _CAN_FILTER_26 as word = 26
    _CAN_FILTER_27 as word = 27
    _CAN_FILTER_28 as word = 28
    _CAN_FILTER_29 as word = 29
    _CAN_FILTER_30 as word = 30
    _CAN_FILTER_31 as word = 31

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
dim Buffers as byte[2*8*16] absolute 0xA0000000

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

main:
  AD1PCFG = 0xFFFF
  PORTB  = 0
  TRISB  = 0

  Can_Init_Flags   = 0
  Can_Send_Flags   = 0
  Can_Rcv_Flags    = 0

  Can_Send_Flags   =
                      _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_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

  CAN1AssignBuffer(@Buffers)
  CAN1ConfigureFIFO(_CAN_BUFFER_0, 8, _CAN_FIFO_RX and _CAN_FULL_MESSAGE)
  CAN1ConfigureFIFO(_CAN_BUFFER_1, 8, _CAN_FIFO_TX and _CAN_TX_NO_RTR_FRAME and _CAN_TX_PRIORITY_3)

  CAN1SetMask(_CAN_MASK_0, -1, _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_XTD_MSG)   ' set all mask1 bits to ones
  CAN1SetFilter(_CAN_FILTER_0, ID_2nd, _CAN_MASK_0, _CAN_BUFFER_0, _CAN_CONFIG_XTD_MSG)   ' set id of filter_B1_F1 to 1st node ID

  CAN1SetOperationMode(_CAN_MODE_NORMAL,0xFF)            ' set NORMAL mode

  RxTx_Data[0] = 9
  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
          LATB = 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
dim Buffers as byte[2*8*16] absolute 0xA0000000

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

main:
  AD1PCFG = 0xFFFF
  PORTB  = 0
  TRISB  = 0

  Can_Init_Flags   = 0
  Can_Send_Flags   = 0
  Can_Rcv_Flags    = 0

  Can_Send_Flags =
                     _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_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
  CAN1AssignBuffer(@Buffers)
  CAN1ConfigureFIFO(_CAN_BUFFER_0, 8, _CAN_FIFO_RX and _CAN_FULL_MESSAGE)
  CAN1ConfigureFIFO(_CAN_BUFFER_1, 8, _CAN_FIFO_TX and _CAN_TX_NO_RTR_FRAME and _CAN_TX_PRIORITY_3)

  CAN1SetMask(_CAN_MASK_3, -1, _CAN_CONFIG_MATCH_MSG_TYPE and _CAN_CONFIG_XTD_MSG)   ' set all mask1 bits to ones
  CAN1SetFilter(_CAN_FILTER_31, ID_1st, _CAN_MASK_3, _CAN_BUFFER_0, _CAN_CONFIG_XTD_MSG)   ' set id of filter_B1_F1 to 1st node ID

  CAN1SetOperationMode(_CAN_MODE_NORMAL,0xFF) ' set NORMAL mode
          TRISD = 0
  while TRUE
      Msg_Rcvd = CAN1Read(Rx_ID , RxTx_Data , Rx_Data_Len, Can_Rcv_Flags)
      LATD = Can_Rcv_Flags
      if ((Rx_ID = ID_1st) and (Msg_Rcvd <> 0)) <> 0 then
          LATB   = 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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