TMS320F28P650DH: SysConfig configuration of CAN peripheral with AUXCLK

Hi team,

In the TRM, I don't see an option for selecting AUXCLK as a clock source in the CANABCLKSEL register, however, it is available in the clock tree of SysConfig - 

Is this an error in the TRM or SysConfig?

Thanks

Hi Dhruva,

Which version of SysConfig and C2000Ware are you using? 

Thanks,

Ira

Hi Ira,

SysConfig - 1.28.0

C2000ware - 26.1.0.00

Thanks,

Dhruva

Hi Dhruva,

I observed that the sysconfig generated board.c does not have any code related to the clock source, which is weird. I'll check on this.

Meanwhile as a workaround, you can override sysconfig generated and manually initialize the CAN module so you aren't blocked by this

For example it can look something like this, please check the driverlib APIs correctly in C:\ti\c2000\C2000Ware_26_01_00_00\driverlib\f28p65x\driverlib\can.c and C:\ti\c2000\C2000Ware_26_01_00_00\driverlib\f28p65x\driverlib\can.h

void initCAN_with_AUXCLK(void)
{
// Step 1: Hardware clock routing (Manually overriding SysConfig)
// This must happen AFTER Device_init()
CAN_selectClockSource(CAN_BASE, CAN_CLOCK_SOURCE_AUXCLK);

// Step 2: Configure Bit-Timing for 500kHz
CAN_ConfigParams canCfg = {
.brp = 1U, // Prescaler = 2
.tseg1 = 14U, // 14 TQ
.tseg2 = 5U, // 5 TQ
.sjw = 1U, // 1 TQ
.enableLoopBack = false,
.enableListenOnly = false
};

// Step 3: Apply configuration
CAN_initModule(CAN_BASE, &canCfg);
CAN_enableModule(CAN_BASE);
}

int main(void)
{
Device_init(); // Generated by SysConfig (sets default SYSCLK)
Device_initGPIO(); // Generated by SysConfig

initCAN_with_AUXCLK(); // Your custom manual configuration

while(1) {
// Application loop
}
}

make sure to add this in a separate .c file and NOT in the board.c (as this will get regenerated every time your rebuild the project)

You can try this workaround while I check why the actual sys config gui does not work.

Hi Ira,

I was able to get CAN up and running at 500khz with AUXCLK with this initialization - 

void Can_Init()
{
    CAN_disableAllMessageObjects(CANA_BASE);

    CAN_disableController(CANA_BASE);

    CAN_selectClockSource(CANA_BASE, CAN_CLOCK_SOURCE_AUX); //set clk source to aux

    CAN_enableController(CANA_BASE);

    //
    // Initialize the CAN controllers
    //
    CAN_initModule(CANA_BASE);

    //
    // Set up the CAN bus bit rate to 500kHz for each module
    // Refer to the Driver Library User Guide for information on how to set
    // tighter timing control. Additionally, consult the device data sheet
    // for more information about the CAN module clocking.
    //
   
    CAN_setBitRate(CANA_BASE, DEVICE_OSCSRC_FREQ, 500000, 20);  //20MHz auxclk freq

    //
    // Enable CAN Auto-Bus-On
    //
    CAN_enableAutoBusOn(CANA_BASE);

    //
    // Set Auto-Bus-On Timer - 300 Sysclock cycles
    //
    CAN_setAutoBusOnTime(CANA_BASE, 300);
    
    /*
    ...interrupt configs
    */
}

Apart from the code generation issue of clock source, please answer these - 

1. What is the functionality of SysConfig>CAN>'Bit Rate Parameters'>'Device SYSCLK MHz'? What value is to be added in this field when clock is not derived from CPU SYSCLK (PERx.SYSCLK)? 

2. "In the TRM, I don't see an option for selecting AUXCLK as a clock source in the CANABCLKSEL register, however, it is available in the clock tree of SysConfig" Please confirm if this is an error in TRM.

Additionally, I noticed that in the CAN examples (C2000Ware > English > Devices > F28P65X > F28P650DK9 > Examples > Driverlib > c28x > can), apart from ex 1 (loopback) and ex 7 (loopback_tx_rx_remote_frame), the other examples have EMPTY SysConfig files (c2000.syscfg) with NO configurations! Please do fix this as well. 

Thanks,

Dhruva 

Hi Dhruv,

1. Enter the actual frequency of whatever source you are routing to CAN (e.g., 20 MHz for AUXCLK, 10 MHz for LSPCLK, etc.). Enter the value in MHz.

2. Im confirming with the team that owns TRM creation/ maintenance. If they confirm, I will file it as a litbug and have it fixed.

Thanks,

Ira