Interrupt Latency
For the timer, IRQx, and SPORT interrupts, latency is at least three full
cycles from the time when an interrupt occurs to the time when the first
instruction of the service routine is executed. This latency is shown in
Figure3-2. Two cycles are required to synchronize the interrupt inter-
nally, assuming that setup and hold times are met (for the IRQx input
pins).

Since interrupts are only serviced on instruction boundaries, before execu-
tion continues, the instruction(s) executed during these two cycles must
be fully completed, including any extra cycles inserted due to Bus
Request/Bus Grant or memory wait states.

#include <HardwareCAN.h>
//#include "changes.h"
/*
*
*/

#define T_DELAY 10
// Instanciation of CAN interface
HardwareCAN canBus(CAN1_BASE);
CanMsg msg;

void CAN_a_33_Setup(void)
{
CAN_STATUS Stat;
canBus.map(CAN_GPIO_PA11_PA12);
Stat = canBus.begin(CAN_SPEED_33, CAN_MODE_NORMAL);
canBus.filter(0, 0, 0);
canBus.set_irq_mode();
Stat = canBus.status();
if (Stat != CAN_OK)
{digitalWrite(PC13, LOW);
delay(10000);}
// /* Your own error processing here */ ; // Initialization failed
// delay(T_DELAY);
}

void CAN_b_95_Setup(void)
{
canBus.map(CAN_GPIO_PB8_PB9);
Stat = canBus.begin(CAN_SPEED_95, CAN_MODE_NORMAL);
canBus.filter(0, 0, 0);
canBus.set_irq_mode();
Stat = canBus.status();
if (Stat != CAN_OK)
{digitalWrite(PC13, LOW);
delay(10000);}
// /* Your own error processing here */; // Initialization failed
// delay(T_DELAY);
}


CAN_TX_MBX CANsend(CanMsg *pmsg)
{
CAN_TX_MBX mbx;

do
{
mbx = canBus.send(pmsg);
#ifdef USE_MULTITASK
vTaskDelay( 1 ); // Infinite loops are not multitasking-friendly
#endif
}
while(mbx == CAN_TX_NO_MBX); // Waiting outbound frames will eventually be sent, unless there is a CAN bus failure.
return mbx;
}

// Send message
// Prepare and send a frame containing some value
void SendCANmessage(long id=0x001, byte dlength=8, byte d0=0x00, byte d1=0x00, byte d2=0x00, byte d3=0x00, byte d4=0x00, byte d5=0x00, byte d6=0x00, byte d7=0x00)
{
// Initialize the message structure
// A CAN structure includes the following fields:
msg.IDE = CAN_ID_STD; // Indicates a standard identifier; CAN_ID_EXT would mean this frame uses an extended identifier
msg.RTR = CAN_RTR_DATA; // Indicated this is a data frame, as opposed to a remote frame (would then be CAN_RTR_REMOTE)
msg.ID = id; // Identifier of the frame : 0-2047 (0-0x3ff) for standard idenfiers; 0-0x1fffffff for extended identifiers
msg.DLC = dlength; // Number of data bytes to follow

// Prepare frame : send something
msg.Data[0] = d0;
msg.Data[1] = d1;
msg.Data[2] = d2;
msg.Data[3] = d3;
msg.Data[4] = d4;
msg.Data[5] = d5;
msg.Data[6] = d6;
msg.Data[7] = d7;

digitalWrite(PC13, LOW); // turn the onboard LED on
CANsend(&msg); // Send this frame
digitalWrite(PC13, HIGH); // turn the LED off
delay(T_DELAY);
}


// The application program starts here
byte msgD0 = 0x00;
void setup() { // Initialize the CAN module and prepare the message structures.
pinMode(PC13, OUTPUT);
digitalWrite(PC13, HIGH);
delay(10);
digitalWrite(PC13, LOW);
delay(1000);
digitalWrite(PC13, HIGH);
delay(1000);

}

void loop() {
CAN_a_33_Setup();
delay(T_DELAY);
SendCANmessage(0x100,1,msgD0);
delay(T_DELAY);
CAN_b_95_Setup();
delay(T_DELAY);
SendCANmessage(0x111,1,msgD0);
delay(T_DELAY);
msgD0++;
}