DUE_CAN HEX Variable

Official Hardware Mega Due
1

Hello Forum Members,

I need help with the DUE_CAN library. What I want to do is create a variable that will change the value in a message to be transmitted using the DUE_CAN Library from Collin80 on GitHub. I will use the example code from the library with a little tweaking to try and explain what I mean.

\Code from Library
CAN_FRAME myFrame;
myFrame.id = 45;
myFrame.length = 1
myFrame.data.bytes[0] = 0x00;
Can0.sendFrame(myFrame);

What I want to do is make the 0x00 a variable place holder. ex.
myFrame.data.bytes[0] = (MyVariable);
What datatype can I use for the variable where I can assign my variable to be a HEX value that will be sent over the can bus?

If this will not work or someone has a better method please let me know. I am open to any suggestions.

Thank you

2

Snippet from the header file:

//This is architecture specific. DO NOT USE THIS UNION ON ANYTHING OTHER THAN THE CORTEX M3 / Arduino Due
//UNLESS YOU DOUBLE CHECK THINGS!
typedef union {
    uint64_t value;
	struct {
		uint32_t low;
		uint32_t high;
	};
	struct {
        uint16_t s0;
		uint16_t s1;
		uint16_t s2;
		uint16_t s3;
    };
	uint8_t bytes[8];
	uint8_t byte[8]; //alternate name so you can omit the s if you feel it makes more sense
} BytesUnion;

typedef struct
{
	uint32_t id;		// EID if ide set, SID otherwise
	uint32_t fid;		// family ID
	uint8_t rtr;		// Remote Transmission Request
	uint8_t priority;	// Priority but only important for TX frames and then only for special uses.
	uint8_t extended;	// Extended ID flag
	uint8_t length;		// Number of data bytes
	BytesUnion data;	// 64 bits - lots of ways to access it.
} CAN_FRAME;
3

Thank you for your response. As you can probably already tell by my questions I don't have much experience coding. My response is this. Based upon the snippet provided can I make my variable a uint8_t data type? Would this work correctly or would I be violating a language rule trying to use a variable where I want to? Could I use something like this:

uint8_t myVariable;

myFrame.data.bytes[0] = ("%#x\n", myVariable); or could I just use (myVariable);

4

You make your variables uint8_t. Then you just assign the variable to the data byte:

uint8_t someVariable =0xDE;
myFrame.data.byte[0] = someVariable;