Importing DBC files
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In this guide we will use a sample J1939 DBC file j1393.dbc that is a slightly altered version of the demo file provided in this introduction to CAN DBC files.
VERSION ""
NS_ :
NS_DESC_
CM_
BA_DEF_
BA_
VAL_
CAT_DEF_
CAT_
FILTER
BA_DEF_DEF_
EV_DATA_
ENVVAR_DATA_
SGTYPE_
SGTYPE_VAL_
BA_DEF_SGTYPE_
BA_SGTYPE_
SIG_TYPE_REF_
VAL_TABLE_
SIG_GROUP_
SIG_VALTYPE_
SIGTYPE_VALTYPE_
BO_TX_BU_
BA_DEF_REL_
BA_REL_
BA_DEF_DEF_REL_
BU_SG_REL_
BU_EV_REL_
BU_BO_REL_
SG_MUL_VAL_
BS_:
BU_:
BO_ 2364539904 EEC1: 8 Vector__XXX
SG_ EngineSpeed : 24|16@1+ (0.125,0) [0|8031.875] "rpm" Vector__XXX
BO_ 2566844672 CCVS1: 8 Vector__XXX
SG_ WheelBasedVehicleSpeed : 8|16@1+ (0.00390625,0) [0|250.996] "km/h" Vector__XXX
CM_ BO_ 2364539904 "Electronic Engine Controller 1";
CM_ SG_ 2364539904 EngineSpeed "Actual engine speed which is calculated over a minimum crankshaft angle of 720 degrees divided by the number of cylinders.…";
CM_ BO_ 2566844672 "Cruise Control/Vehicle Speed 1";
CM_ SG_ 2566844672 WheelBasedVehicleSpeed "Wheel-Based Vehicle Speed: Speed of the vehicle as calculated from wheel or tailshaft speed.";
BA_DEF_ SG_ "SPN" INT 0 524287;
BA_DEF_ BO_ "VFrameFormat" ENUM "StandardCAN","ExtendedCAN","reserved","J1939PG";
BA_DEF_ "DatabaseVersion" STRING ;
BA_DEF_ "BusType" STRING ;
BA_DEF_ "ProtocolType" STRING ;
BA_DEF_ "DatabaseCompiler" STRING ;
BA_DEF_DEF_ "SPN" 0;
BA_DEF_DEF_ "VFrameFormat" "J1939PG";
BA_DEF_DEF_ "DatabaseVersion" "";
BA_DEF_DEF_ "BusType" "";
BA_DEF_DEF_ "ProtocolType" "";
BA_DEF_DEF_ "DatabaseCompiler" "";
BA_ "ProtocolType" "J1939";
BA_ "BusType" "CAN";
BA_ "DatabaseCompiler" "CSS ELECTRONICS (WWW.CSSELECTRONICS.COM)";
BA_ "DatabaseVersion" "1.0.0";
BA_ "VFrameFormat" BO_ 2364539904 3;
BA_ "SPN" SG_ 2364539904 EngineSpeed 190;
BA_ "SPN" SG_ 2566844672 WheelBasedVehicleSpeed 84;
First of all we need to load the CANBUS system model that contains all SA Engine functions for working with CAN bus data.
You can disregard any JSON.parse errors that might arise.
system_models:load("canbus");
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Then we start by translating the DBC file to our SA Engine CANBUS wrapper OSQL format.
can:import_dbc(sa_home() + "models/canbus-guide/j1939.dbc",
sa_home() + "models/canbus-guide/j1939_dbc.osql",
[]);
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The query translates the sample J1939 DBC file and stores the result in j939_dbc.osql:
/* CAN frame 0x0CF00400 BO_ 2364539904 */
create can:signal (name, cid, fid, decoder, params, options) instances
("EEC1_EngineSpeed", 0, 0x0CF00400, #'can:unpack_scale',['Z24u16', 0.125, 0],{"min":0,"max":8031.875});
/* CAN frame 0x18FEF100 BO_ 2566844672 */
create can:signal (name, cid, fid, decoder, params, options) instances
("CCVS1_WheelBasedVehicleSpeed", 0, 0x18FEF100, #'can:unpack_scale',['Z08u16', 0.00390625, 0],{"min":0,"max":250.996});
We see that the OSQL file contains two CAN signals "EEC1_EngineSpeed" and "CCVS1_WheelBasedVehicleSpeed". Now that we have an OSQL definition of the DBC file we can simply load it.
load_osql(sa_home() + "models/canbus-guide/j1939_dbc.osql");
To run this code block you must be logged in and your studio instance must be started.
Loading the same signal definitions multiple times with load_osql(<osql-dbc-file>) result in "Violating unique index for name(Signal s)->Charstring" errors. To prevent this you can delete previously loaded signals with delete_objects(select cs from can:signal cs) before loading signal definitions.
To verify that the signals were defined we can list all signals and see that "EEC1_EngineSpeed" and "CCVS1_WheelBasedVehicleSpeed" are present in the output.
signals();
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