Skip to content

CAN Configurations

CAN Bus#

With Customer Bus selected in the explorer, the configurable options available affect all Buffers and their associated CAN messages.

Expanding the Bus node displays the Buffers and CAN messages configured for the Bus.

CAN Bus Configuration

Customer Bus Panel

Option Description
Buffer Count The number of Buffers available for configuration on the selected Bus.
Global Mask The receive mask for all Buffers that do not have a configurable Receive Mask. Note: Not all control units support a configurable global mask.
Link Speed Select a speed in kbits for the selected Bus from the drop-down list.

Parameter Block Panel

Received Measurement Parameters for the CAN bus are stored in a single contiguous block of memory.

Parameter Description
Ctrl Id The Control Id of the memory block.
Parameter Address The start address of the memory block.
Block Size The size of the memory block in number of blocks.

Buffers#

With a Buffer selected, the configurable options available apply to that Buffer only.

CAN Buffer Configuration

Note

The CAN messages associated with this buffer are listed in the Messages node for this CAN Bus.

Add a CAN Message to an Empty Buffer

  1. Select a Buffer
  2. Click Add
  3. In the Add MessageId dialog box, select a Message Id from the drop-down list and click OK

The CAN message is assigned to the selected Buffer. When a specific Message is selected in the explorer, the Buffer to which it is assigned is shown in the Message Details. A CAN message can only be assigned to one Buffer.

Note

Buffers can be configured individually as described above, or existing Buffer configurations can be Imported. See Import/Export Buffers and Messages.

Mode Panel

Define the mode of the CAN messages configured for this buffer.

Mode Description
Not Configured Any messages configured for this buffer will not be included in the logging.
Receive CAN messages are in receive mode.
Transmit CAN messages are in transmit mode.

Buffer Panel

Option Description
Receive Mask Any bits that are zero in the Receive Mask are ignored when comparing a received dataframe's ID against the acceptance ID of the buffer. For example, if the receive mask is set to 0xFFFFFFF0 and ID of the first message is 0x210, then the buffer will receive all messages in the range 0x210 to 0x21F. Note: Not all buffers have a configurable receive mask.
Rate The time between each message being transmitted in ms.
Message Count The number of CAN messages configured for the selected Buffer.

Messages Panel

The Messages Window lists the IDs of CAN messages currently configured for this buffer.

Action Description
Add Click to add a CAN message to the selected buffer.
Delete Click to delete the selected Message Id.

CAN Messages

CAN Messages#

With the Messages node selected, the New Message button is displayed to allow new CAN messages to be added to the Configuration.

To add a CAN message, click New Message and enter a Message ID in the Add Message ID dialog box. The new message is added to the list.

Note

CAN messages can be added and configured individually as described above, or existing CAN Message configurations can be Imported. See Import/Export Buffers and Messages.

To view the CAN messages configured for the CAN Bus, expand the Messages Node. With an individual CAN message selected, the configurable options apply to that message only. Use these commands to configure the CAN message and to add new Parameters as required.

Message Panel

Option Description
Message Id The unique CAN identifier for the selected CAN message.
Description Enter a short description of the CAN message.
Message Length Enter the length of the CAN message. For CAN messages with multiplexed data, the length must be the same for all multiplexer values.
Buffer The Buffer to which the selected CAN message is assigned. (Read only)
Parameter Count The number of Parameters associated with the selected CAN message.
Mode TRANSMIT / RECEIVE / NOT CONFIGURED - The Mode of the selected CAN message (the same for all messages in that Buffer).
New Parameter Opens the Add Parameter dialog box.

Multiplexed Panel

Multiplexed CAN messages allow more measurement parameters to be received by a CAN buffer than can be packed into a single CAN message.

Option Description
Multiplexed Select this checkbox to multiplex some or all of the CAN message data.
ByteOrder Select the byte order of the multiplexer: MSB First or MSB Last.
StartBit Select the position within the CAN message data where the multiplexer value starts.
BitLength The length, in bits, of the multiplexer value. Maximum length is 16.
MultiplexerValues When transmitting this message, multiplexed messages in the range of 0 to Multiplexer Values - 1 will be sent.

Parameter Details#

With a specific Parameter selected, the configurable options available apply to that Parameter only.

CAN Parameter Configuration

Parameter Panel

Option Description
Parameter The name of the Parameter. For received Parameters, this is the name displayed by System Monitor and ATLAS. For transmitted Parameters, this is the name of the parameter to be transmitted.
Properties Open the Parameter Properties dialog box to edit the Parameter Properties.
Start Bit Select the position within the CAN message data where the Measurement Parameter starts. Note: When MSB Last is selected as the Byte Order, the default Start Bit shows the normalised value. For a parameter at the start of a CAN Message, the Start Bit is shown as 0, although its underlying value is 7.
Bit Length Select the length in bits of the Measurement Parameter. Maximum length is 32.
Value Select whether the Measurement Parameter is Signed, Unsigned, or Floating Point. If Floating Point is selected, the Bit Length must be set at 32.

Scaling Panel

Option Description
Gain Set the gain for converting a scaled value into a raw value.
Offset Set the offset for converting a scaled value into a raw value.

Scaling Formula: 

Raw Value = GAIN × Scaled Value + OFFSET

Byte Order

Select the byte order of the Measurement Parameter: - MSB First - MSB Last

Multiplexer Panel#

ID

If the message is multiplexed, the multiplexer ID defines which multiplexed messages the parameter will be in.

A Measurement Parameter can be defined in more than one multiplexed message, since the multiplexer ID is a combined value and mask:

  • 0, 1, or X can be used for each bit in the multiplexer ID, where X means that bit does not matter
  • For example, if a measurement parameter is in all messages with an even multiplexer value, the multiplexer ID should be set to XXXXXXXXXX0

Value

The Parameter is transmitted/received if the value equals the multiplexer value for the message currently being processed, after any bits in the mask are ignored.

Mask

Calculated from the entered multiplexer ID and defines which bits of the multiplexer value should be ignored when determining whether to include this parameter in the message.

CAN Bit Definitions#

For each Measurement Parameter and multiplexer value, the start bit, length, and byte order must be defined. Bits and bytes within a CAN message are numbered sequentially from left to right.

MSB First Format Values#

When a Measurement Parameter or multiplexer value is defined as MSB_FIRST, the start bit defines the location of the most significant bit. The progression of bits and bytes is to the right.

MSB First Format

MSB Last Format Values#

When a Measurement Parameter or multiplexer value is defined as MSB_LAST, the start bit defines the location of the least significant bit. The progression of bits is to the left and the progression of bytes is to the right.

MSB Last Format

Note

  • In an MSB Last word, the Start Bit is the last bit of the first byte. Whilst the Start Bit for the word at the start of a CAN message is bit 0, the Start Bit in terms of MSB is bit 7. When a Parameter is added to the CAN Message, the CAN Configure dialog automatically displays normalised values for the Start Bit. For example, if the Parameter appears at the start of a CAN Message, the value 0 is shown, although its underlying value is 7. The Start Bit of a 2nd Parameter is shown as 8, although its underlying value is 15, and so on.
  • When a CAN message is exported, the saved Start Bit values are the actual values and not the normalised values shown in the dialog box. These can be seen in the Start Bit column of the .csv Export files.

CAN Parameters#

When a CAN Configuration file is added to the project, a CAN Parameters folder is added to the System Monitor Explorer. This folder contains CAN Parameters configured in the ECU, which can be associated with CAN Receive messages.

Note

Parameters associated with Transmit CAN messages are not listed in the CAN Parameters folder. However, for a Parameter to be associated with a CAN Transmit message, it must exist in the ECU Measurement Parameters folder.

Add a CAN Parameter

To associate a new Parameter with a CAN message:

  1. Select a message and click New Parameter to open the Add Parameter dialog box
  2. Name - Enter the name of a Parameter to associate with the selected CAN message
    • Note: For a Parameter to be selected for a Transmit message, it must be listed in the ECU Measurement Parameters folder in the System Monitor Explorer.
    • Click to browse for a Parameter in the Select Parameter dialog box
  3. Click OK to associate the Parameter with the selected CAN message

Import/Export Buffers and Messages#

Existing Buffer Configuration (.csv) files and Message Configuration files can be imported into the CAN configuration. Buffer and Message configurations can be exported from the CAN Configuration as .csv files.

Note

When importing Buffer Configuration files or Message Configuration files, all Buffer/Message configurations are overwritten by the imported file.

Import/Export Buffer Configuration Files#

  1. Select Logging > CAN Configuration to open the CAN Configuration dialog box
  2. Expand the CAN Bus and select Buffers
  3. Right-click and select Import Buffer or Export Buffer

Import/Export Message Configuration Files#

  1. Select Logging > CAN Configuration to open the CAN Configuration dialog box
  2. Expand the CAN Bus and select Messages
  3. Right-click and select Import Messages or Export Messages

CSV File Formats#

Buffer and CAN message CSV import files must be formatted as described below.

Buffer CSV File Format

Col Name Description
1 Buffer The number of the buffers in the CAN Bus.
2 Direction Mode of the CAN messages configured for this buffer. TX = Transmit, RX = Receive, Blank = not configured.
3 RX Mask The Receive Mask value, if one is configured for the buffer. Blank = not configured.
4 Rate[ms] The time (ms) between each CAN message being transmitted.
5 Messages The CAN message ID configured for the buffer. If more than one CAN message is configured, they must be comma-separated.

CAN Message CSV File Format

Following a change in the representation of the Parameter Start Bit, v2 of the CAN Message CSV format is now in use. When parameters are set as MSB Last, the value in the .csv is now represented by the logical bit position.

v2 files are identified by the text v2 as the first value in the header row. All exported files now conform to the new format; both formats can be imported.

Col Name Description
1 CAN ID The CAN message ID. 11-bit IDs: 0 to 0x7FF. 29-bit IDs: 0 to 0x1FFFFFFF
2 Message Length The CAN message length.
3 Start Bit Multiplexer messages - the position within the CAN message data where the multiplexer value starts.
4 Length Multiplexer messages - the length, in bits, of the multiplexer value. Maximum length is 16.
5 Byte Order Multiplexer messages - the byte order of the multiplexer: MSB First or MSB Last. Note: If the Message is not multiplexed, columns 3, 4, and 5 are blank.
6 Parameter Name The name of the Parameter associated with the CAN message. If more than one, subsequent parameters are listed on a new line.
7 Start Bit The position within the CAN message data where the Measurement Parameter starts.
8 Length The length in bits of the Measurement Parameter. Maximum length is 32.
9 Multiplexer ID The multiplexer ID defines which multiplexed messages the parameter will be in.
10 Signed Whether the Measurement Parameter is signed: YES or NO. If Floating Point, this column must be NO.
11 Floating Point Whether the Measurement Parameter is Floating Point.
12 Byte Order The byte order of the Measurement Parameter: MSB First or MSB Last.
13 Scaling Gain Parameter property. The Gain set for converting a scaled value into a raw value.
14 Scaling Offset Parameter property. The Offset set for converting a scaled value into a raw value.
15 Description Parameter property - Description.
16 Display Format Display format.
17 Units Display units.
18 Lower Limit Lower value limit.
19 Upper Limit Upper value limit.
20 Identifier CAN Parameter unique identifier.
21 Display Limit Low Lower display limit.
22 Display Limit High Higher display limit.

CAN Configuration Compare#

CAN Configuration Compare lets you inspect two .clc CAN configurations side‑by‑side and optionally merge any differences back into the active document before downloading the result to an ECU.

  1. Launch System Monitor
    • Ensure the project you want to update has a CAN configuration document open in System Monitor (this becomes the Main side of the dialog).

  2. Choose Logging > CAN Configuration Compare from the menu or press Ctrl+F9. System Monitor briefly locks communications and runs offline while the dialog is open to prevent background threads from modifying writable CAN parameters.

    • The dialog stays on top until you press Save (applies changes) or Cancel (closes without modifying the active CAN configuration).

      CAN Configuration Compare

    Reading the comparison

    • The dialog is divided into two mirrored panes. The Main pane (left) is read-only and always reflects the currently active CAN configuration; its text box shows the full path of that document.
    • The Compare pane (right) starts empty. Click the ... button to open any .clc file. You can only open documents that use the CAN configuration template, and only the first CAN configuration inside that file is used for comparison.
    • The Compare text box and label update with the loaded file name. Press Unload to drop the comparison document, empty the right tree, and clear the copy buttons so you can start over with another file.
    • Check Show Differences Only to hide every node that matches (green items), leaving only the red nodes that carry mismatches. Unchecking the box reruns the comparison to reveal the full structure again.
    • Both trees use color‑coding: green nodes match, while red nodes differ or are unmatched in the opposite tree. The parent branches also turn red when any child is different.
    • Clicking a node on either side automatically selects its best match on the other tree and opens the detail panel below it. Each side hosts a dedicated detail mini-dialog, so you can inspect either bus-level, buffer-level, message-level, or parameter-level properties without leaving the window.
    • Bus detail panel shows name, buffer count, global mask, link speed, controller ID, parameter address, and block size.
    • Buffer detail panel shows the buffer name, receive mask, rate, number of messages, and the list order of those messages.
    • Message detail panel lists the description, standard/frame flag, buffer assignment, message length, parameter count, multiplexing attributes, byte order, start bit, bit length, and the number of values.
    • Parameter detail panel surfaces the parameter name, start bit, bit length, signed/unsigned, byte order, scaling gain/offset, multiplexer ID/value, and mask.
    • The detail panels highlight only the fields that differ.
    • Right-clicking on the Compare tree pops up a context menu that mirrors the </<< buttons and shows tooltip text (e.g., “Merge 'MainBus' details”).

    CAN Configuration Compare

  3. Merging differences

    • The < button (Copy Selected) copies the currently highlighted Compare node into the Main tree. It works for buses, buffers, messages, and parameters. The command overwrites the selected node, and—when appropriate—adds missing messages or parameters to the Main configuration and preserves existing parameter objects.
    • The << button (Copy All) is designed for whole branches. When you select a bus or message and press <<, the dialog copies that node plus every child buffer/message/parameter so the entire subtree matches the Compare side.
    • Both buttons remain disabled until you select a red node in the Compare tree, and the selection also enables the detail panels for a quick sanity check.
    • After any merge, the dialog reruns the comparison, collapses/expands the tree to refresh the view, and re-evaluates the Show Differences Only filter.

  4. When you are happy with the merged result, click Save (default button) to close the dialog with IDOK.

    • If System Monitor is connected to an ECU and the ECU is not running in read-only mode, you will see the prompt: “Do you want to download a new logging configuration to the ECU?” Confirming that prompt pushes the merged configuration down to the ECU.
    • If the ECU connection is not available or CAN-only behavior is enabled, System Monitor exports the merged CAN messages instead.
    • Press Cancel to close the dialog without persisting any merges. The temporary configuration copy is discarded, and the active CAN configuration remains untouched.

Tip

  • Always load the correct base CAN configuration before opening the compare dialog—the left tree is read-only and cannot be swapped inside the dialog.
  • Unload a compare file before selecting a different one to avoid keeping multiple documents open at the same time.
  • You can toggle Show Differences Only at any time to keep the trees focused on mismatches; unchecking the box reruns the comparison and shows every node again.
  • The Compare tree tries to match nodes by name or ID, so renamed buses/messages may still appear as differences even when the parameters inside line up.
  • Right-click on the Compare side to see context-aware merge descriptions and to invoke the same </<< actions without moving your mouse to the buttons.
  • After closing the dialog with Save, use the standard System Monitor workflow to save the project and to revisit any downstream logging or download steps.