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How does a VBOX use CAN

The robust nature of CAN Bus has meant that it has become widely used in industry for carrying measurement data in harsh environments. Because of this, Racelogic adopted CAN Bus as a method for transferring data between the VBOX data loggers and external modules such as the ADC03 and TC8.

The VBOX uses CAN in two ways:

  • The first is simply to transmit GPS data for use with the Multifunction display or other third party loggers. The format of the GPS data within the messages is fixed and documented in the various VBOX user guides.
  • The second way that VBOX uses CAN Bus is, as previously mentioned, to communicate with external Racelogic modules. When a VBOX is first powered up, it scans the CAN Bus, looking for any Racelogic modules. If a module is found, the VBOX will send out a CAN message to request data from it in synchronisation with incoming GPS data. The module will reply to the VBOX request with its measured input value (temperature, yawrate, voltage, etc). The CAN identifiers used by the VBOX to communicate with the external modules are based on the type of module and the module serial number. This allows the VBOX to individually access each module on the CAN Bus.

 

The standard bus rate for CAN on a VBOX network is 500Kbit, although it can be changed to other values. Typical Baud rates used for CAN Bus communication range from 125Kbit, 250Kbit, 500Kbit up to a maximum of 1Mbit.

 

Racelogic CAN Operating Modes

Racelogic Mode

  • This should be set if a Racelogic module is to be used with a Racelogic VBOX. All CAN parameters are set to work with the Racelogic VBOX CAN protocol.
 

User Polled CAN Mode

  • This mode allows a customer to use their own datalogging system to poll a Racelogic Module for data. In this way, the output timing of the sensor can be synchronised with other CAN Information. The following parameters are all used and so must be set:

Baud Rate
Extended Identifiers (On or Off)
Request Identifiers
Response Identifiers
Timer (this has no effect in this mode)

Timed CAN Mode

  • In this mode, the module will send CAN data at intervals determined by the timer value. The following parameters are all used and so must be set:


Baud Rate
Extended Identifiers
Request Identifiers (these have no effect in this mode)
Response Identifiers
Timer (time interval in milliseconds between output data)

 

See also

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Last modified
17:12, 12 Aug 2014

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