CAN

The TMS302F28335 offers two CAN-Interfaces: CAN_A and CAN_B. Each Interface needs one RX and one TX Pin for receive and transmit operations. Each Interface can only be used one time.

Each CAN-Module can use up to 32 mailboxes. Use 0-15 for Tx-operations, and 16-31 for Rx- operation.

For configuration of mailboxes, user needs to create an object of type CanMailbox and assign values for Identifier, extended Identifier, messageLength, direction and active/inactive to respective object.

For extended Identifier = 0, the Identifier-length will be 11 bit. Identifier values are valid from 0x00 to 0x7FF.
For extended Identifier = 1, the Identifier-length will be 29 bit. Identifier values are valid from 0x00 to 0x1FFF FFFF.
Messages are priorized by lowest identifier first

Amount of data-bytes that will be sent or received via a mailbox, needs to be configured by assigning a value to messageLength attribute of CanMailbox object. The maximal length for receive and transmit operations is 8 byte. Variable msg for CAN-operations in example code is of type Uint64. Using a variable of Uint64 for receive and transmit operations enables the module to read and write all bytes (in case of messageLength = 8).

---

	RX	TX
CAN_A	GPIO18 / GPIO30	GPIO19 / GPIO31
CAN_B	GPIO10 / GPIO13 / GPIO17 / GPIO21	GPIO8 / GPIO12 / GPIO16 / GPIO20

---

Code example

#include "global_defines.h"                                 //Include global_defines.h
#include "system_controls/system_controls.h"                //Include module of system controls
#include "can/can.h"                                        //Include module of CAN
 
Uint16 runProgram=True;                                     //Declaration of global variable
 
CanInterface CAN_A = {GPIO30, GPIO31};                      //Instantiate CANInterface and assign GPIO30 and GPIO31 to CAN_A
CanMailbox CAN_MB_0 = {0x00, 0, 0, CAN_Rx, 1};              //Instantiate CAN-Mailbox: Identifier 0x00, extended 0 (no), messageLength in Byte (0), direction CAN_Rx (receive), active (1) as CAN_MB_0
CanMailbox CAN_MB_1 = {0x01, 0, 4, CAN_Rx, 1};              //Instantiate CAN-Mailbox: Identifier 0x01, extended 0 (no), messageLength in Byte (4), direction CAN_Rx (receive), active (1) as CAN_MB_1
CanMailbox CAN_MB_2 = {0x02, 0, 2, CAN_Tx, 1};              //Instantiate CAN-Mailbox: Identifier 0x02, extended 0 (no), messageLength in Byte (2), direction CAN_Tx (transmit), active (1) as CAN_MB_2
 
void main(void){
    int result = 0;                                         //Optional: can be used to check return values of functions
    Uint64 msg = 0;                                         //Create variables for CAN-operations
    int mBYTES[4];
    setSystemControls();                                    //Call setSystemControls() function
    result = init_CAN(CAN_A, 100000);                       //Init CAN_A peripheral with baudrate of 100 kHz. Returns result of operation
 
    CAN_setupMailbox(CAN_A, 0, &CAN_MB_0);                  //Setup mailbox CAN_MB_0 and assign mailbox-number 0 to Mailbox CAN_MB_0
    CAN_setupMailbox(CAN_A, 1, &CAN_MB_1);                  //Setup mailbox CAN_MB_1 and assign mailbox-number 1 to Mailbox CAN_MB_1
    CAN_setupMailbox(CAN_A, 2, &CAN_MB_2);                  //Setup mailbox CAN_MB_2 and assign mailbox-number 2 to Mailbox CAN_MB_2
    
    while(runProgram){
        if (CAN_dataAvailableAtMailbox(CAN_A, 0)){           //Check if mailbox message available at CAN_A mailbox0
            CAN_getDataFromMailbox(CAN_A, 0, &msg, CAN_MB_0.messageLength); //Save message from CAN_A mailbox 0 in variable msg
            runProgram=False;                                //Stop program, because of received message on CAN_A mailbox 0
        }
        else if(CAN_dataAvailableAtMailbox(CAN_A, 1)){       //Check if mailbox message available at CAN_A mailbox 1
            CAN_getDataFromMailbox(CAN_A, 1, &msg, CAN_MB_1.messageLength); //Save message from CAN_A mailbox 0 in variable msg
 
            mBYTES[0] = (msg >> 0) & 0xFF;                   //Copy CAN message byte 0 in mBytes[0]
            mBYTES[1] = (msg >> 8) & 0xFF;                   //Copy CAN message byte 1 in mBytes[1]
            mBYTES[2] = (msg >> 16) & 0xFF;                  //Copy CAN message byte 2 in mBytes[2]
            mBYTES[3] = (msg >> 24) & 0xFF;                  //Copy CAN message byte 3 in mBytes[3]
            msg = 0;                                         //Clean msg data
        }
        
        msg = 0x1122;                                        //Setup Data for transmission
        CAN_sendDataOnMailbox(CAN_A, 2, &msg, CAN_MB_2.messageLength);   //Send Data msg on Tx mailbox-number 2
    }
}

---

Documented C-Code of module:

CAN

---

Detailed description in Technical Reference Manual:

Technical_Reference_Manual