PGN Handling

The J1939 Protocol Stack keeps all PGNs which are handled by the device in a list. The list is added to the J1939 Protocol Stack by the function J1939_PgnAddList(). The elements inside this list are administrated by the user.

PGN Reception

A PGN which shall be received by the J1939 Protocol Stack has to be marked with the symbol J1939_MSG_RCV inside the control field of the structure J1939_PGN_Entry_ts (J1939_PGN_Entry_s::uwControl).

The following example shows the setup of a PGN with a value of 0 which is received by the ECU.

   // Torque/Speed Control 1 (TSC1)
   //
   { J1939_PRIORITY_INFO | J1939_MSG_RCV,             // PDU Control
     (uint32_t) 0,                                    // PGN value
     (uint16_t) 2000,                                 // Reception timeout value
     (uint16_t) 0,                                    // Counter
     (uint8_t)  0,                                    // DA
     (uint8_t)  0,                                    // reserved
     (uint16_t) 8,                                    // Data size
     ECU_Pgn00000                                     // PGN handler
   },

Upon reception of the TSC1 PDU the function ECU_Pgn00000() is called.

static int16_t ECU_Pgn00000(uint8_t * pubDataV, uint16_t uwSizeV, uint8_t ubSrcAddrV, uint8_t ubNetV)
{
   J1939_Payload_ts  *ptsPayloadT = (J1939_Payload_ts *) pubDataV;
   uint16_t          uwSpeedT;
 
   //---------------------------------------------------------------------------------------------------
   // silence warning for unused parameters
   //
   (void) uwSizeV;
   (void) ubSrcAddrV;
   (void) ubNetV;
 
   //---------------------------------------------------------------------------------------------------
   // copy received data
   //
   uwSpeedT   = ptsPayloadT->aubByte[2];
   uwSpeedT <<= 8;
   uwSpeedT  += ptsPayloadT->aubByte[1];
 
   tsECU_ControlS.ubDevice = ubSrcAddrV;
   tsECU_ControlS.ubMode   = ptsPayloadT->aubByte[0];
   tsECU_ControlS.uwSpeed  = uwSpeedT;
   tsECU_ControlS.ubTorque = ptsPayloadT->aubByte[3];
 
   return ((int16_t) eJ1939_HANDLER_RESULT_OK);
}

PGN Transmission

A PGN which shall be transmitted by the J1939 Protocol Stack has to be marked with the symbol J1939_MSG_TRM inside the control field of the structure J1939_PGN_Entry_ts (J1939_PGN_Entry_s::uwControl). For a cyclic PGN transmission, the cycle time field (J1939_PGN_Entry_s::uwCycle) is set to a value unequal to zero.

The following example shows the setup of a PGN with a value of 61444 which is transmitted by ECU with a cycle time of 10 ms.

   // Electronic Engine Controller 1 (EEC1)
   //
   { J1939_PRIORITY_CTRL | J1939_MSG_TRM,             // PDU Control
     (uint32_t) 61444,                                // PGN value
     (uint16_t) (PGN_TRANSMISSION_RATE),              // Transmission rate
     (uint16_t) 0,                                    // Counter
     (uint8_t)  0,                                    // DA
     (uint8_t)  0,                                    // reserved
     (uint16_t) 8,                                    // Data size
     ECU_Pgn61444                                     // PGN handler
   },

After the cycle timer has elapsed, the function ECU_Pgn61444() is called, which is the interface to the application. The following example shows the implementation of the function ECU_Pgn61444().

static int16_t ECU_Pgn61444(uint8_t * pubDataV, uint16_t uwSizeV, uint8_t ubSrcAddrV, uint8_t ubNetV)
{
   J1939_Payload_ts  *ptsPayloadT = (J1939_Payload_ts *) pubDataV;
   static uint16_t   uwSpeedS  = 200 * 8;             // 1 Bit = 0.125rpm
   static uint8_t    ubTorqueS = (uint8_t) 125;       // 1 Bit = 1%, -125% Offset
   static uint8_t    ubSimDirS = 1;                   // direction of simulation
 
   //---------------------------------------------------------------------------------------------------
   // silence warning for unused parameters
   //
   (void) uwSizeV;
   (void) ubSrcAddrV;
   (void) ubNetV;
 
   //---------------------------------------------------------------------------------------------------
   // simulate torque
   //
   ubTorqueS += (uint8_t) 1;
   if (ubTorqueS > ((uint8_t) 200))
   {
      ubTorqueS = (uint8_t) 125;
   }
 
   //---------------------------------------------------------------------------------------------------
   // simulate engine speed in rpm between 200 and 2200
   //
   if (tsECU_ControlS.uwSpeed == (uint16_t) 0)
   {
      if (ubSimDirS == (uint8_t) 1)
      {
         uwSpeedS = uwSpeedS + (uint16_t) 8;
         if (uwSpeedS / (uint16_t) 8 > (uint16_t) 2200)
         {
            ubSimDirS = 0;
         }
      }
      else
      {
         uwSpeedS = uwSpeedS - (uint16_t) 8;
         if (uwSpeedS / (uint16_t) 8 < (uint16_t) 200)
         {
            ubSimDirS = 1;
         }
      }
   }
 
   //---------------------------------------------------------------------------------------------------
   // set engine speed to the requested value
   //
   else
   {
      //-------------------------------------------------------------------------------------------
      // requested value is greater
      //
      if (tsECU_ControlS.uwSpeed > uwSpeedS)
      {
         uwSpeedS = uwSpeedS + (uint16_t) 8;
      }
 
      //-------------------------------------------------------------------------------------------
      // requested value is smaller
      //
      if (tsECU_ControlS.uwSpeed < uwSpeedS)
      {
         uwSpeedS = uwSpeedS - (uint16_t) 8;
      }
   }
 
 
   ptsPayloadT->aubByte[0] = 0x01;
   ptsPayloadT->aubByte[1] = ubTorqueS;                     // SPN 512
   ptsPayloadT->aubByte[2] = ubTorqueS;                     // SPN 513
   ptsPayloadT->aubByte[3] = (uint8_t) uwSpeedS;            // SPN 190
   ptsPayloadT->aubByte[4] = (uint8_t) (uwSpeedS >> 8);
   ptsPayloadT->aubByte[5] = tsECU_ControlS.ubDevice;       // Controlling device
   ptsPayloadT->aubByte[6] = J1939_UNUSED_UINT8;
   ptsPayloadT->aubByte[7] = J1939_UNUSED_UINT8;
 
   return ((int16_t) eJ1939_HANDLER_RESULT_OK);
}