SocketCAN DUNE implementation

CANbus support was not present in DUNE, and therefore had to be added. Since the Raspberry Pi on the Otter is using Linux, we can use the SocketCAN package, which comes with the Linux kernel by default.

Many DUNE tasks use an interface defined by IO::Handle, and so does this CAN implementation. This means that there will be little difference between using CAN or Serial in DUNE. The biggest difference is that CAN uses addresses, and so must have functions to set and get these. This also enables use of the Poll::poll function, and makes it possible to only read the SocketCAN buffer when there is something in it. Reading it without checking will result in the task waiting until a CAN message is received. An example of reading with the DUNE socketCAN implementation is:

if (Poll::poll(*m_can, 0.01)) {
 m_can->readString(m_can_bfr, sizeof(m_can_bfr));  // Read from CAN bus
 id = m_can->getRXID();  // Address of the most previously read message. Must be called after a read to yield desired data.
}

Here, m_can_bfr is a char array that is used to store the data read from CAN. Writing to the CAN bus can be done like this:

m_can_bfr[0] = 0x4f;
m_can_bfr[1] = 0x74;
m_can_bfr[2] = 0x74;
m_can_bfr[3] = 0x65;
m_can_bfr[4] = 0x72;

m_can->setTXID(0x0000feab);
m_can->write(m_can_bfr, 5);

Here, m_can_bfr still is a char array. Thats it!

• Linux kernel documentation on CAN