Decoding multiple message of CAN bus method - c

Question

I have a CAN bus message that is composed from 3 parts.
What is the best way to decode it ?
My thinking is to use 3 FIFOs when the first part is decompsed, I store it in the FIFO, and the same for the other 2 parts.
Then I combine those 3 Fifos togethers into one message.
The total message length is 64bytes PDU Lenght
I'm using the following function to get can bus data
HAL_CAN_GetRxMessage
can bus

Answer 1

Using the answer to your previous question from here, you can use that bitfield in combination with a plain uint8_t [64]. For example
typedef struct
{
uint8_t data[64];
can_received_t received;
} msg_t;
Fill up with data as you receive it, writing it to the corresponding data bytes, then set the bit to indicate that the message has been partially received. The struct isn't regarded as complete until you have received all parts.
A queue/FIFO only fills one purpose, and that is to delay execution of something until later, when there's more time. There's no reason to do that here. Your CAN message decoding could look something like:
msg_t msg;
switch(received_can_id)
{
...
case CANID_FOO:
memcpy(&msg.data[FOO_INDEX], rec_data, FOO_SIZE);
msg.received |= RECEIVED_FOO;
break;
case CANID_BAR:
memcpy(&msg.data[BAR_INDEX], rec_data, BAR_SIZE);
msg.received |= RECEIVED_BAR;
break;
...
}
if(msg.received == RECEIVED_ALL)
{
use(&msg); // do something
memset(&msg, 0, sizeof msg); // reset everything
}
This is fairly quick code, no need to queue anything.

Answer 2

Considering the standard CAN message is of size 8bytes length, you can declare message as uin64_t and combine the respective signals into message using |.
Example:
uint64_t message = 0;
uint8_t incomingBytes[8] = {0};
for(int i=0; i<8; i++)
{
message = message <<8;
message |= incomingBytes[i];
}
If you want to interpret VIN data as string then,
char vindata [9];
memcpy(vindata, incomingBytes, 8);
vindata[8] = '\0';