To get a higher level of abstraction, CAN Signals and Messages can be used to abstract information mappings to the Bus communication objects. In this topic example, the information from the 'Nodestatus' and 'CPU-Load' will be sent in a CAN Frame called 'Status' and updated through a CAN Frame called 'Command' with the following Signal and Message definitions:
Signal Configuration
The Message Configuration below uses CAN Signals. Before CAN Messages can be used, each CAN signal must be configured accordingly. The Signal Configuration can be found in can_cfg.c. However, the "Signal Enumerations" are typically found in can_cfg.h. Signals allow the user to not worry about where a given signal if found within a CAN Frame, while containing different types of data. For more information about CAN Signals click Here.
Note:
- A CAN Signal can be defined without any CAN communication knowledge. No information about sending or receiving information is needed during configuration.
#include "can_sig.h"
enum { [1] /* ---------------- SIGNAL ENUMERATIONS --------------- */
S_NODESTATUS = 0,
S_CPULOAD,
S_MAX,
};
const CANSIG_PARA CanSig[CANSIG_N] = { [2]
/* ---------------- SIGNAL NODESTATUS ----------------- */
{CANSIG_UNCHANGED, [3A] /* Initial Status */
1, [B] /* Width in Bytes */
0, [C] /* Initial Value */
#if (CANSIG_CALLBACK_EN > 0)
StatusChange}, [D] /* Callback Function: User Defined */
#else
},
#endif
/* ----------------- SIGNAL CPULOAD ------------------- */
{CANSIG_UNCHANGED, [3A] /* Initial Status */
1, [B] /* Width in Bytes */
0, [C] /* Initial Value */
#if (CANSIG_CALLBACK_EN > 0)
0} [D] /* No Callback */
#else
},
#endif
};
Message Configuration
The Message Configuration can be found in can_cfg.c. However, the "Message Enumerations" are typically found in can_cfg.h. Please note that CAN Signals must be configured prior to be used in CAN Messages. For more information on CAN Messages click Here.
Note:
- A CAN Message can be defined without any knowledge of the information generated and/or the usage of the payload. Only the mapping of the payload (and it's respective parts) must be known.
#include "can_msg.h"
enum { [1] /* --------------- MESSAGE ENUMERATIONS --------------- */
M_STATUS = 0,
M_COMMAND,
M_MAX
};
const CANMSG_PARA CanMsg[CANMSG_N] = [2]
{
/* ------------------ MESSAGE STATUS ------------------ */
{ 0x123L, [3A] /* CAN-Identifier */
CANMSG_TX, [B] /* Message Type */
2, [C] /* DLC of Message */
2, /* No. of Links */
{ { S_NODESTATUS, [D] /* Signal ID */
0 }, [E] /* Byte Position */
{ S_CPULOAD, /* Signal ID */
2 } /* Byte Position */
},
},
/* ----------------- MESSAGE COMMAND ------------------ */
{ 0x122L, [4A] /* CAN-Identifier */
CANMSG_RX, [B] /* Message Type */
1, [C] /* DLC of Message */
1, /* No. of Links */
{ { S_NODESTATUS, [D] /* Signal ID */
0 } [E] /* Byte Position */
}
}
};