Add support for 29 bit identifier

[danjo133]

Hi,

I need to have support for 29 bit identifiers in a project I'm working on.

I have working code for it that I would like to contribute, but I'm unsure what the best way of handling the 11 vs 29 bit difference.

I have added a bool for keeping track of if it's a 29 or 11 bit identifier
typedef struct
{
uint32_t id;
struct {
int8_t rtr : 1;
uint8_t length : 4;
} header;
uint8_t data[8];
bool extended;
} tCAN;

I would like to keep all old code working though, and I have two suggestions. Either change the mcp2515.c to .cpp which would allow constructors that set default extended=false or add a new struct for extended messages. Do you have any other suggestion?

[wellsa1]

Same problem here. Do you still have this code?

[danjo133]

I have a 29 bit branch here, also changed to c++, but it should be split into separate commits. Haven't touched it for a couple years though.

https://github.com/danjo133/SparkFun_CAN-Bus_Arduino_Library

[wellsa1]

Thanks for the reply!! I'll give it a go. I'm assuming the usage hasn't changed.

[danjo133]

Not that I remember, just check extended flag in tCAN on receive and set it on send.

[bessman]

@danjo133 Your implementation misidentifies all incoming frames as extended. I've fixed it in my branch: https://github.com/bessman/SparkFun_CAN-Bus_Arduino_Library

[danjo133]

Good to know, thanks!