cannot.ino

#include "wiring_private.h"
#include <sam.h>
#include <component/can.h>
#include <component/gclk.h>
#include <instance/can0.h>
#include <instance/gclk.h>

#define GCLK_CAN GCLK_PCHCTRL_GEN_GCLK1_Val
#define FREQ VARIANT_GCLK1_FREQ

struct can_tx_buf {
    CAN_TXBE_0_Type txb0;
    CAN_TXBE_1_Type txb1;
    __attribute__((aligned(4)))
    uint8_t data[8];
};

__attribute__((section("canram")))
can_tx_buf tx_buffer;

#define CAN_RX_PIN (15)
#define CAN_TX_PIN (14)
#define CAN_GROUP (1)
#define CAN_FUNCTION ((EPioType)7)
// the setup function runs once when you press reset or power the board
void setup() {
    pinPeripheral(41, CAN_FUNCTION);
    pinPeripheral(42, CAN_FUNCTION);

    GCLK->PCHCTRL[CAN1_GCLK_ID].reg = GCLK_CAN | (1 << GCLK_PCHCTRL_CHEN_Pos);
    GCLK->PCHCTRL[CAN1_GCLK_ID].reg = GCLK_CAN | (1 << GCLK_PCHCTRL_CHEN_Pos);

    // reset and allow configuration change
    CAN1->CCCR.bit.INIT = 1;
    while (!CAN1->CCCR.bit.INIT) {
    }
    CAN1->CCCR.bit.CCE = 1;

    CAN1->MRCFG.reg = 0;

    {
        CAN_CCCR_Type cccr = {};
        cccr.bit.CCE = 1;
        cccr.bit.TEST = 1;
        CAN1->CCCR.reg = cccr.reg;
    }

    // 1MHz
    {
        CAN_DBTP_Type dbtp = {};
        dbtp.bit.DBRP = 0;
        dbtp.bit.DTSEG1 = 40-2;
        dbtp.bit.DTSEG2 = 8-1;
        dbtp.bit.DSJW = 3;
        CAN1->DBTP.reg = dbtp.reg;
    }

    {
        CAN_TEST_Type test = {};
        // test.bit.LBCK = 1,
        CAN1->TEST.reg = test.reg;
    }


    // 1MHz
    {
        CAN_NBTP_Type nbtp;
        nbtp.bit.NBRP = 0;
        nbtp.bit.NTSEG1 = 40-2;
        nbtp.bit.NTSEG2 = 8-1;
        nbtp.bit.NSJW = 3;
        CAN1->NBTP.reg = nbtp.reg;
    }

    // max 8 byte payload
    {
        CAN_TXESC_Type esc = {};
        esc.bit.TBDS = CAN_TXESC_TBDS_DATA8_Val;
        CAN1->TXESC.reg = esc.reg;
    }

    {
        CAN_TXBC_Type bc = {};
        bc.bit.TBSA = (uint32_t)&tx_buffer,
        bc.bit.NDTB = 1;
        bc.bit.TFQM = 0; // Messages are transmitted in the order submitted
        CAN1->TXBC.reg = bc.reg;
    }


    CAN1->CCCR.bit.CCE = 0;
    CAN1->CCCR.bit.INIT = 0;
    while(CAN1->CCCR.bit.INIT) {
    }

    Serial.begin(9600); // open the serial port at 9600 bps:
    // initialize digital pin LED_BUILTIN as an output.
    pinMode(LED_BUILTIN, OUTPUT);
}

static uint64_t i = 0;
// the loop function runs over and over again forever
void loop() {
    Serial.print("CAN hardware info\n");
    Serial.print("Version ");
    Serial.print(CAN1->CREL.bit.REL);
    Serial.print(".");
    Serial.print(CAN1->CREL.bit.STEP);
    Serial.print(".");
    Serial.print(CAN1->CREL.bit.SUBSTEP);
    Serial.println("\n");

    i = i + 1;
    Serial.println((long)i, HEX);
    memcpy(&tx_buffer.data, &i, sizeof(tx_buffer.data));
    tx_buffer.txb0.bit.ID = 0x408 << 18;
    tx_buffer.txb1.bit.DLC = 8;
    
    Serial.print("CAN ECR x");
    Serial.println(CAN1->ECR.reg, HEX);
    Serial.print("CAN PSR x");
    Serial.println(CAN1->PSR.reg, HEX);

    if(CAN1->PSR.bit.BO) {
        Serial.println("Manual reset");
        CAN1->CCCR.bit.INIT = 0;
        while(CAN1->CCCR.bit.INIT) {
        }
    }

    CAN1->TXBAR.reg = 1;
    for(int i=0; (CAN1->TXBTO.reg & 1) && (i<8); i++) {
        delay(1);                       // wait for message to transmit
    }
    Serial.print("CAN TXBTO x");
    Serial.println(CAN1->TXBTO.reg, HEX);

    delay(1000);

}