TCP/IP - CAN Bricklet 2.0

This is the description of the TCP/IP protocol for the CAN Bricklet 2.0. General information and technical specifications for the CAN Bricklet 2.0 are summarized in its hardware description.

API

A general description of the TCP/IP protocol structure can be found here.

Basic Functions

BrickletCANV2.write_frame_low_level
Function ID:

1

Request:
  • frame_type -- uint8
  • identifier -- uint32
  • data_length -- uint8
  • data_data -- uint8[15]
Response:
  • success -- bool

Writes a data or remote frame to the write queue to be transmitted over the CAN transceiver.

The Bricklet supports the standard 11-bit (CAN 2.0A) and the additional extended 29-bit (CAN 2.0B) identifiers. For standard frames the Bricklet uses bit 0 to 10 from the identifier parameter as standard 11-bit identifier. For extended frames the Bricklet uses bit 0 to 28 from the identifier parameter as extended 29-bit identifier.

The data parameter can be up to 15 bytes long. For data frames up to 8 bytes will be used as the actual data. The length (DLC) field in the data or remote frame will be set to the actual length of the data parameter. This allows to transmit data and remote frames with excess length. For remote frames only the length of the data parameter is used. The actual data bytes are ignored.

Returns true if the frame was successfully added to the write queue. Returns false if the frame could not be added because write queue is already full or because the write buffer or the write backlog are configured with a size of zero (see set_queue_configuration_low_level).

The write queue can overflow if frames are written to it at a higher rate than the Bricklet can transmitted them over the CAN transceiver. This may happen if the CAN transceiver is configured as read-only or is using a low baud rate (see set_transceiver_configuration). It can also happen if the CAN bus is congested and the frame cannot be transmitted because it constantly loses arbitration or because the CAN transceiver is currently disabled due to a high write error level (see get_error_log_low_level).

The following meanings are defined for the parameters of this function:

  • 0: standard data, for frame_type
  • 1: standard remote, for frame_type
  • 2: extended data, for frame_type
  • 3: extended remote, for frame_type
BrickletCANV2.read_frame_low_level
Function ID:

2

Request:

empty payload

Response:
  • success -- bool
  • frame_type -- uint8
  • identifier -- uint32
  • data_length -- uint8
  • data_data -- uint8[15]

Tries to read the next data or remote frame from the read queue and returns it. If a frame was successfully read, then the success return value is set to true and the other return values contain the frame. If the read queue is empty and no frame could be read, then the success return value is set to false and the other return values contain invalid data.

The identifier return value follows the identifier format described for write_frame_low_level.

The data return value can be up to 15 bytes long. For data frames up to the first 8 bytes are the actual received data. All bytes after the 8th byte are always zero and only there to indicate the length of a data or remote frame with excess length. For remote frames the length of the data return value represents the requested length. The actual data bytes are always zero.

A configurable read filter can be used to define which frames should be received by the CAN transceiver and put into the read queue (see set_read_filter_configuration).

Instead of polling with this function, you can also use callbacks. See the set_frame_read_callback_configuration function and the CALLBACK_FRAME_READ_LOW_LEVEL callback.

The following meanings are defined for the parameters of this function:

  • 0: standard data, for frame_type
  • 1: standard remote, for frame_type
  • 2: extended data, for frame_type
  • 3: extended remote, for frame_type
BrickletCANV2.set_transceiver_configuration
Function ID:

5

Request:
  • baud_rate -- uint32
  • sample_point -- uint16
  • transceiver_mode -- uint8
Response:

no response

Sets the transceiver configuration for the CAN bus communication.

The baud rate can be configured in bit/s between 10 and 1000 kbit/s and the sample point can be configured in 1/10 % between 50 and 90 %.

The CAN transceiver has three different modes:

  • Normal: Reads from and writes to the CAN bus and performs active bus error detection and acknowledgement.
  • Loopback: All reads and writes are performed internally. The transceiver is disconnected from the actual CAN bus.
  • Read-Only: Only reads from the CAN bus, but does neither active bus error detection nor acknowledgement. Only the receiving part of the transceiver is connected to the CAN bus.

The default is: 125 kbit/s, 62.5 % and normal transceiver mode.

The following meanings are defined for the parameters of this function:

  • 0: normal, for transceiver_mode
  • 1: loopback, for transceiver_mode
  • 2: read only, for transceiver_mode
BrickletCANV2.get_transceiver_configuration
Function ID:

6

Request:

empty payload

Response:
  • baud_rate -- uint32
  • sample_point -- uint16
  • transceiver_mode -- uint8

Returns the configuration as set by set_transceiver_configuration.

The following meanings are defined for the parameters of this function:

  • 0: normal, for transceiver_mode
  • 1: loopback, for transceiver_mode
  • 2: read only, for transceiver_mode

Advanced Functions

BrickletCANV2.set_queue_configuration_low_level
Function ID:

7

Request:
  • write_buffer_size -- uint8
  • write_buffer_timeout -- int32
  • write_backlog_size -- uint16
  • read_buffer_sizes_length -- uint8
  • read_buffer_sizes_data -- int8[32]
  • read_backlog_size -- uint16
Response:

no response

Sets the write and read queue configuration.

The CAN transceiver has 32 buffers in total in hardware for transmitting and receiving frames. Additionally, the Bricklet has a backlog for 768 frames in total in software. The buffers and the backlog can be freely assigned to the write and read queues.

write_frame_low_level writes a frame into the write backlog. The Bricklet moves the frame from the backlog into a free write buffer. The CAN transceiver then transmits the frame from the write buffer to the CAN bus. If there are no write buffers (write_buffer_size is zero) or there is no write backlog (write_backlog_size is zero) then no frames can be transmitted and write_frame_low_level returns always false.

The CAN transceiver receives a frame from the CAN bus and stores it into a free read buffer. The Bricklet moves the frame from the read buffer into the read backlog. read_frame_low_level reads the frame from the read backlog and returns it. If there are no read buffers (read_buffer_sizes is empty) or there is no read backlog (read_backlog_size is zero) then no frames can be received and read_frame_low_level returns always false.

There can be multiple read buffers, because the CAN transceiver cannot receive data and remote frames into the same read buffer. A positive read buffer size represents a data frame read buffer and a negative read buffer size represents a remote frame read buffer. A read buffer size of zero is not allowed. By default the first read buffer is configured for data frames and the second read buffer is configured for remote frame. There can be up to 32 different read buffers, assuming that no write buffer is used. Each read buffer has its own filter configuration (see set_read_filter_configuration).

A valid queue configuration fulfills these conditions:

write_buffer_size + read_buffer_size_0 + read_buffer_size_1 + ... + read_buffer_size_31 <= 32
write_backlog_size + read_backlog_size <= 768

The write buffer timeout has three different modes that define how a failed frame transmission should be handled:

  • Single-Shot (< 0): Only one transmission attempt will be made. If the transmission fails then the frame is discarded.
  • Infinite (= 0): Infinite transmission attempts will be made. The frame will never be discarded.
  • Milliseconds (> 0): A limited number of transmission attempts will be made. If the frame could not be transmitted successfully after the configured number of milliseconds then the frame is discarded.

The current content of the queues is lost when this function is called.

The default is:

  • 8 write buffers,
  • infinite write timeout,
  • 383 write backlog frames,
  • 16 read buffers for data frames,
  • 8 read buffers for remote frames and
  • 383 read backlog frames.
BrickletCANV2.get_queue_configuration_low_level
Function ID:

8

Request:

empty payload

Response:
  • write_buffer_size -- uint8
  • write_buffer_timeout -- int32
  • write_backlog_size -- uint16
  • read_buffer_sizes_length -- uint8
  • read_buffer_sizes_data -- int8[32]
  • read_backlog_size -- uint16

Returns the queue configuration as set by set_queue_configuration_low_level.

BrickletCANV2.set_read_filter_configuration
Function ID:

9

Request:
  • buffer_index -- uint8
  • filter_mode -- uint8
  • filter_mask -- uint32
  • filter_identifier -- uint32
Response:

no response

Set the read filter configuration for the given read buffer index. This can be used to define which frames should be received by the CAN transceiver and put into the read buffer.

The read filter has four different modes that define if and how the filter mask and the filter identifier are applied:

  • Accept-All: All frames are received.
  • Match-Standard-Only: Only standard frames with a matching identifier are received.
  • Match-Extended-Only: Only extended frames with a matching identifier are received.
  • Match-Standard-And-Extended: Standard and extended frames with a matching identifier are received.

The filter mask and filter identifier are used as bit masks. Their usage depends on the mode:

  • Accept-All: Mask and identifier are ignored.
  • Match-Standard-Only: Bit 0 to 10 (11 bits) of filter mask and filter identifier are used to match the 11-bit identifier of standard frames.
  • Match-Extended-Only: Bit 0 to 28 (29 bits) of filter mask and filter identifier are used to match the 29-bit identifier of extended frames.
  • Match-Standard-And-Extended: Bit 18 to 28 (11 bits) of filter mask and filter identifier are used to match the 11-bit identifier of standard frames, bit 0 to 17 (18 bits) are ignored in this case. Bit 0 to 28 (29 bits) of filter mask and filter identifier are used to match the 29-bit identifier of extended frames.

The filter mask and filter identifier are applied in this way: The filter mask is used to select the frame identifier bits that should be compared to the corresponding filter identifier bits. All unselected bits are automatically accepted. All selected bits have to match the filter identifier to be accepted. If all bits for the selected mode are accepted then the frame is accepted and is added to the read buffer.

Filter Mask Bit Filter Identifier Bit Frame Identifier Bit Result
0 X X Accept
1 0 0 Accept
1 0 1 Reject
1 1 0 Reject
1 1 1 Accept

For example, to receive standard frames with identifier 0x123 only, the mode can be set to Match-Standard-Only with 0x7FF as mask and 0x123 as identifier. The mask of 0x7FF selects all 11 identifier bits for matching so that the identifier has to be exactly 0x123 to be accepted.

To accept identifier 0x123 and identifier 0x456 at the same time, just set filter 2 to 0x456 and keep mask and filter 1 unchanged.

There can be up to 32 different read filters configured at the same time, because there can be up to 32 read buffer (see set_queue_configuration_low_level).

The default mode is accept-all for all read buffers.

The following meanings are defined for the parameters of this function:

  • 0: accept all, for filter_mode
  • 1: match standard only, for filter_mode
  • 2: match extended only, for filter_mode
  • 3: match standard and extended, for filter_mode
BrickletCANV2.get_read_filter_configuration
Function ID:

10

Request:
  • buffer_index -- uint8
Response:
  • filter_mode -- uint8
  • filter_mask -- uint32
  • filter_identifier -- uint32

Returns the read filter configuration as set by set_read_filter_configuration.

The following meanings are defined for the parameters of this function:

  • 0: accept all, for filter_mode
  • 1: match standard only, for filter_mode
  • 2: match extended only, for filter_mode
  • 3: match standard and extended, for filter_mode
BrickletCANV2.get_error_log_low_level
Function ID:

11

Request:

empty payload

Response:
  • transceiver_state -- uint8
  • transceiver_write_error_level -- uint8
  • transceiver_read_error_level -- uint8
  • transceiver_stuffing_error_count -- uint32
  • transceiver_format_error_count -- uint32
  • transceiver_ack_error_count -- uint32
  • transceiver_bit1_error_count -- uint32
  • transceiver_bit0_error_count -- uint32
  • transceiver_crc_error_count -- uint32
  • write_buffer_timeout_error_count -- uint32
  • read_buffer_overflow_error_count -- uint32
  • read_buffer_overflow_error_occurred_length -- uint8
  • read_buffer_overflow_error_occurred_data -- bool[32]
  • read_backlog_overflow_error_count -- uint32

Returns information about different kinds of errors.

The write and read error levels indicate the current level of stuffing, form, acknowledgement, bit and checksum errors during CAN bus write and read operations. For each of this error kinds there is also an individual counter.

When the write error level extends 255 then the CAN transceiver gets disabled and no frames can be transmitted or received anymore. The CAN transceiver will automatically be activated again after the CAN bus is idle for a while.

The write buffer timeout, read buffer and backlog overflow counts represents the number of these errors:

  • A write buffer timeout occurs if a frame could not be transmitted before the configured write buffer timeout expired (see set_queue_configuration_low_level).
  • A read buffer overflow occurs if a read buffer of the CAN transceiver still contains the last received frame when the next frame arrives. In this case the last received frame is lost. This happens if the CAN transceiver receives more frames than the Bricklet can handle. Using the read filter (see set_read_filter_configuration) can help to reduce the amount of received frames. This count is not exact, but a lower bound, because the Bricklet might not able detect all overflows if they occur in rapid succession.
  • A read backlog overflow occurs if the read backlog of the Bricklet is already full when the next frame should be read from a read buffer of the CAN transceiver. In this case the frame in the read buffer is lost. This happens if the CAN transceiver receives more frames to be added to the read backlog than are removed from the read backlog using the read_frame_low_level function. Using the CALLBACK_FRAME_READ_LOW_LEVEL callback ensures that the read backlog can not overflow.

The read buffer overflow counter counts the overflows of all configured read buffers. Which read buffer exactly suffered from an overflow can be figured out from the read buffer overflow occurrence list (read_buffer_overflow_error_occurred).

The following meanings are defined for the parameters of this function:

  • 0: active, for transceiver_state
  • 1: passive, for transceiver_state
  • 2: disabled, for transceiver_state
BrickletCANV2.set_communication_led_config
Function ID:

12

Request:
  • config -- uint8
Response:

no response

Sets the communication LED configuration. By default the LED shows CAN-Bus traffic, it flickers once for every 40 transmitted or received frames.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is off.

The following meanings are defined for the parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show communication, for config
BrickletCANV2.get_communication_led_config
Function ID:

13

Request:

empty payload

Response:
  • config -- uint8

Returns the configuration as set by set_communication_led_config

The following meanings are defined for the parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show communication, for config
BrickletCANV2.set_error_led_config
Function ID:

14

Request:
  • config -- uint8
Response:

no response

Sets the error LED configuration.

By default (show-transceiver-state) the error LED turns on if the CAN transceiver is passive or disabled state (see get_error_log_low_level). If the CAN transceiver is in active state the LED turns off.

If the LED is configured as show-error then the error LED turns on if any error occurs. If you call this function with the show-error option again, the LED will turn off until the next error occurs.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is off.

The following meanings are defined for the parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show transceiver state, for config
  • 4: show error, for config
BrickletCANV2.get_error_led_config
Function ID:

15

Request:

empty payload

Response:
  • config -- uint8

Returns the configuration as set by set_error_led_config.

The following meanings are defined for the parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show transceiver state, for config
  • 4: show error, for config
BrickletCANV2.get_spitfp_error_count
Function ID:

234

Request:

empty payload

Response:
  • error_count_ack_checksum -- uint32
  • error_count_message_checksum -- uint32
  • error_count_frame -- uint32
  • error_count_overflow -- uint32

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

BrickletCANV2.set_bootloader_mode
Function ID:

235

Request:
  • mode -- uint8
Response:
  • status -- uint8

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following meanings are defined for the parameters of this function:

  • 0: bootloader, for mode
  • 1: firmware, for mode
  • 2: bootloader wait for reboot, for mode
  • 3: firmware wait for reboot, for mode
  • 4: firmware wait for erase and reboot, for mode
  • 0: ok, for status
  • 1: invalid mode, for status
  • 2: no change, for status
  • 3: entry function not present, for status
  • 4: device identifier incorrect, for status
  • 5: crc mismatch, for status
BrickletCANV2.get_bootloader_mode
Function ID:

236

Request:

empty payload

Response:
  • mode -- uint8

Returns the current bootloader mode, see set_bootloader_mode.

The following meanings are defined for the parameters of this function:

  • 0: bootloader, for mode
  • 1: firmware, for mode
  • 2: bootloader wait for reboot, for mode
  • 3: firmware wait for reboot, for mode
  • 4: firmware wait for erase and reboot, for mode
BrickletCANV2.set_write_firmware_pointer
Function ID:

237

Request:
  • pointer -- uint32
Response:

no response

Sets the firmware pointer for write_firmware. The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickletCANV2.write_firmware
Function ID:

238

Request:
  • data -- uint8[64]
Response:
  • status -- uint8

Writes 64 Bytes of firmware at the position as written by set_write_firmware_pointer before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickletCANV2.set_status_led_config
Function ID:

239

Request:
  • config -- uint8
Response:

no response

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following meanings are defined for the parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show status, for config
BrickletCANV2.get_status_led_config
Function ID:

240

Request:

empty payload

Response:
  • config -- uint8

Returns the configuration as set by set_status_led_config

The following meanings are defined for the parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show status, for config
BrickletCANV2.get_chip_temperature
Function ID:

242

Request:

empty payload

Response:
  • temperature -- int16

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

BrickletCANV2.reset
Function ID:243
Request:empty payload
Response:no response

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

BrickletCANV2.write_uid
Function ID:

248

Request:
  • uid -- uint32
Response:

no response

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

BrickletCANV2.read_uid
Function ID:

249

Request:

empty payload

Response:
  • uid -- uint32

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

BrickletCANV2.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here

Callback Configuration Functions

BrickletCANV2.set_frame_read_callback_configuration
Function ID:

3

Request:
  • enabled -- bool
Response:

no response

Enables and disables the CALLBACK_FRAME_READ_LOW_LEVEL callback.

By default the callback is disabled.

BrickletCANV2.get_frame_read_callback_configuration
Function ID:

4

Request:

empty payload

Response:
  • enabled -- bool

Returns true if the CALLBACK_FRAME_READ_LOW_LEVEL callback is enabled, false otherwise.

Callbacks

BrickletCANV2.CALLBACK_FRAME_READ_LOW_LEVEL
Function ID:

16

Response:
  • frame_type -- uint8
  • identifier -- uint32
  • data_length -- uint8
  • data_data -- uint8[15]

This callback is triggered if a data or remote frame was received by the CAN transceiver.

The identifier return value follows the identifier format described for write_frame_low_level.

For details on the data return value see read_frame_low_level.

A configurable read filter can be used to define which frames should be received by the CAN transceiver and put into the read queue (see set_queue_configuration_low_level).

To enable this callback, use set_frame_read_callback_configuration.

The following meanings are defined for the parameters of this function:

  • 0: standard data, for frame_type
  • 1: standard remote, for frame_type
  • 2: extended data, for frame_type
  • 3: extended remote, for frame_type