FSL’s CAN software converts many serial style messages into CAN format. Due principally to using NovAtel hardware, in particular SPAN, we had to devise a method of taking extended messages up to seven hundred bytes in length and turning them into eight byte CAN frames.  The concept of CAN is that many devices can hang off the same communications bus and receive specific messages identified by CAN Frame ID#. By example in the screenshot below CAN frame 101 contains UTM X and Y coordinates for Car 1. If we continued to use NovAtel’s format this data would have come in the serial BESTUTM format containing much redundant data that many devices could not read.

A working example of these CAN frames in use could be that of a convertible car with an ECU (Engine Control Unit), ESP (Electronic Stabilisation Programme) and slow-roll roll bars. The ECU might require velocity vectors to compute gradient and distance travelled for predictive fuel flow (Frame 107) while the ESP could also require the same data in addition to that in frames 102 and 103 for interactive steering, drive and suspension input. The slow-roll roll bars could simply need a mix of frames 102 and 103 to detect a slow-roll that so often goes undetected by airbag accelerometers.  The controllers for the ESP, ECU and roll-over bar activation will listen for just their specific messages discarding all others.

FSL’s CAN Configuration software let’s the user take standard NovAtel messages and create an initialisation file that configures the NovAtel receiver to output BETUTM, BESTVEL and INSPVAS. In this case the messages are sent to the CPUCard (with CAN processor) which strips the required data output from the messages and places it into the correct CAN frames (102, 103 and 107) for onward transmission.

The user can change data precision and format by way of a look up table showing how your selected variable would look after change. UTM Eastings and Northings could become two single precision values rather than doubles. The usable precision is still protected but the space to transmit data is compressed and compatible with one eight byte CAN frame. Similarly the four double precision velocity vectors in BESTVEL and INSPVAS can be reduced to four half precision values and packed into the same CAN frame. Meanwhile as you populate the CAN frame an indicator will show you how many bytes remain and the remaining precision and format options.

Once the user has prepared the CAN frame format and ID numbers the settings are stored into an initialisation file in the configuration library. The user can have many project specific initialisation files within the configuration library any of which can be the default file for start-up or reconfiguration while running.