Fix wrong API usage in disable() and beginAutoSpeed()

[sans-ltd]

Hello,
we are using your CAN library in an automotive project on the ESP32-C6 where we have both CAN busses in use.
Thank you for restructuring your library, especially removing the static init of CAN busses and the MCP2517 stuff.
But we still have a crash when using your lib in our scenario.
This is the fix for it.
Feel free to contact us, maybe also for further collaboration.

[jeroenveer]

I have had the same issues and this seems to have fixed the crashes i had.

#74

#80

The issue i have now is that it somehow sees its own transmitted frames and then processes them as received frames.
I externally send a frame to CAN0 it is received and transmitted on CAN1.
CAN1 then sees its own send frame and sends it to CAN0 creating a constant loop.

	CAN_FRAME message;
	if (CAN0.available() && CAN0.read(message)) {
		CAN1.sendFrame(message);
	}

	CAN_FRAME message2;
	if (CAN1.available() && CAN1.read(message2)) {
		CAN0.sendFrame(message2);
	}

[sans-ltd]

I have had the same issues and this seems to have fixed the crashes i had.

#74

#80

The issue i have now is that it somehow sees its own transmitted frames and then processes them as received frames. I externally send a frame to CAN0 it is received and transmitted on CAN1. CAN1 then sees its own send frame and sends it to CAN0 creating a constant loop.

	CAN_FRAME message;
	if (CAN0.available() && CAN0.read(message)) {
		CAN1.sendFrame(message);
	}

	CAN_FRAME message2;
	if (CAN1.available() && CAN1.read(message2)) {
		CAN0.sendFrame(message2);
	}

Yes it seems like I am doing the same thing as you. The trick is to remember the last forwarded frame and ignore it if it appears again. It seems to be a "feature" of the CAN transceiver. If you run candump can0 and cansend can0 some#thing on Linux in parallel, you will also see your sent frames in the candump.

[jeroenveer]

I see the same issue on the older ESP32 boards with single CAN as well. I believe it appeared with the new IDF update so do not think it's a feature of the transceiver.

[jeroenveer]

Which part of the frame would u use to ignore it? you have a example code?

[sans-ltd]

I compare (==) id and length. And then memcmp the data

[sans-ltd]

A full example would be a bit difficult to extract from my code.

[sans-ltd]

I found out the core reason for this looping behavior:
from twai_types.h:

typedef struct {
    union {
        struct {
            //The order of these bits must match deprecated message flags for compatibility reasons
            uint32_t extd: 1;           /**< Extended Frame Format (29bit ID) */
            uint32_t rtr: 1;            /**< Message is a Remote Frame */
            uint32_t ss: 1;             /**< Transmit as a Single Shot Transmission. Unused for received. */
            uint32_t self: 1;           /**< Transmit as a Self Reception Request. Unused for received. */
            uint32_t dlc_non_comp: 1;   /**< Message's Data length code is larger than 8. This will break compliance with ISO 11898-1 */
            uint32_t reserved: 27;      /**< Reserved bits */
        };
        //Todo: Deprecate flags
        uint32_t flags;                 /**< Deprecated: Alternate way to set bits using message flags */
    };
    uint32_t identifier;                /**< 11 or 29 bit identifier */
    uint8_t data_length_code;           /**< Data length code */
    uint8_t data[TWAI_FRAME_MAX_DLC];    /**< Data bytes (not relevant in RTR frame) */
} twai_message_t;

In the example, they set it to 0, for a good reason, since we have a C struct here, it is pure random how it is initialized:

// Configure message to transmit
twai_message_t message = {
    // Message type and format settings
    .extd = 1,              // Standard vs extended format
    .rtr = 0,               // Data vs RTR frame
    .ss = 0,                // Whether the message is single shot (i.e., does not repeat on error)
    .self = 0,              // Whether the message is a self reception request (loopback)
    .dlc_non_comp = 0,      // DLC is less than 8
    // Message ID and payload
    .identifier = 0xAAAA,
    .data_length_code = 4,
    .data = {0, 1, 2, 3},
};

[TechOverflow]

Hi @sans-ltd,
Great find! However in my case, I believe that not only was it repeating the message on the bus that received the message, but I couldn't get the received message on CAN0 to be sent on CAN1. See my issue.

Edit: I now see @jeroenveer already mentioned the issue ;)

[sans-ltd]

BTW: I do not use the synchronous loop code as seen here but a callback:

    CAN0.watchFor();                         
    CAN0.setCallback(0, &CANBusses::onOtherMessageCAN0);

void CANBusses::onOtherMessageCAN0(CAN_FRAME *msg)
{
   ...
   CAN1.sendFrame(*msg);
}

[jeroenveer]

@sans-ltd Awesome! That fixed it thank you!

It runs perfectly with synchronous loop
Tested with load of 90 different CAN frames for about 15 minutes and got 0 missed frames.

	CAN_FRAME message;
	if (CAN0.available() && CAN0.read(message)) {
		CAN1.sendFrame(message);
	}

	CAN_FRAME message2;
	if (CAN1.available() && CAN1.read(message2)) {
		CAN0.sendFrame(message2);
	}

[TechOverflow]

I can confirm that after applying the changes, I can forward thousands of messages back and forth to both buses without a hickup.

[nicolasf]

This PR fixes issues with ESP32-C6 for me.
Without it I have crashes almost immediatelly on the CAN loop.

Thanks @sans-ltd .