ESP32-TWAI-CAN

ESP32 driver library for TWAI / CAN for Adruino using ESP-IDF drivers.

Tested on ESP32 and ESP32-S3.

Usage

Library has everything inside it's header, just include that and then use ESP32Can object to send or receive CanFrame.

Here is simple example how to query and receive OBD2 PID frames:

#include <ESP32-TWAI-CAN.hpp>

// Default for ESP32
#define CAN_TX		5
#define CAN_RX		4


CanFrame rxFrame;

void sendObdFrame(uint8_t obdId) {
	CanFrame obdFrame = { 0 };
	obdFrame.identifier = 0x7DF; // Default OBD2 address;
	obdFrame.extd = 0;
	obdFrame.data_length_code = 8;
	obdFrame.data[0] = 2;
	obdFrame.data[1] = 1;
	obdFrame.data[2] = obdId;
	obdFrame.data[3] = 0xAA;    // Best to use 0xAA (0b10101010) instead of 0
	obdFrame.data[4] = 0xAA;    // CAN works better this way as it needs
	obdFrame.data[5] = 0xAA;    // to avoid bit-stuffing
	obdFrame.data[6] = 0xAA;
	obdFrame.data[7] = 0xAA;
    // Accepts both pointers and references 
    ESP32Can.writeFrame(obdFrame);  // timeout defaults to 1 ms
}

void setup() {
    // Setup serial for debbuging.
    Serial.begin(115200);

    // Set pins
	ESP32Can.setPins(CAN_TX, CAN_RX);
	
    // You can set custom size for the queues - those are default
    ESP32Can.setRxQueueSize(5);
	ESP32Can.setTxQueueSize(5);

    // .setSpeed() and .begin() functions require to use TwaiSpeed enum,
    // but you can easily convert it from numerical value using .convertSpeed()
    ESP32Can.setSpeed(ESP32Can.convertSpeed(500));

    // You can also just use .begin()..
    if(ESP32Can.begin()) {
        Serial.println("CAN bus started!");
    } else {
        Serial.println("CAN bus failed!");
    }

    // or override everything in one command;
    // It is also safe to use .begin() without .end() as it calls it internally
    if(ESP32Can.begin(ESP32Can.convertSpeed(500), CAN_TX, CAN_RX, 10, 10)) {
        Serial.println("CAN bus started!");
    } else {
        Serial.println("CAN bus failed!");
    }
}

void loop() {
    static uint32_t lastStamp = 0;
    uint32_t currentStamp = millis();
    
    if(currentStamp - lastStamp > 1000) {   // sends OBD2 request every second
        lastStamp = currentStamp;
        sendObdFrame(5); // For coolant temperature
    }

    // You can set custom timeout, default is 1000
    if(ESP32Can.readFrame(rxFrame, 1000)) {
        // Comment out if too many requests 
        Serial.printf("Received frame: %03X \r\n", rxFrame.identifier);
        if(rxFrame.identifier == 0x7E8) {   // Standard OBD2 frame responce ID
            Serial.printf("Collant temp: %3d°C \r\n", rxFrame.data[3] - 40); // Convert to °C
        }
    }
}

Advanced

You can also setup your own masks and configurations:

// Everything is defaulted so you can just call .begin() or .begin(TwaiSpeed)
// Calling begin() to change speed works, it will disable current driver first
bool begin(TwaiSpeed twaiSpeed = TWAI_SPEED_500KBPS, 
                int8_t txPin = -1, int8_t rxPin = -1,
                uint16_t txQueue = 0xFFFF, uint16_t rxQueue = 0xFFFF,
                twai_filter_config_t*  fConfig = nullptr,
                twai_general_config_t* gConfig = nullptr,
                twai_timing_config_t*  tConfig = nullptr);

Follow soc/twai_types.h for more info:

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;

/**
 * @brief   Structure for bit timing configuration of the TWAI driver
 *
 * @note    Macro initializers are available for this structure
 */
typedef struct {
    uint32_t brp;                   /**< Baudrate prescaler (i.e., APB clock divider). Any even number from 2 to 128 for ESP32, 2 to 32768 for ESP32S2.
                                         For ESP32 Rev 2 or later, multiples of 4 from 132 to 256 are also supported */
    uint8_t tseg_1;                 /**< Timing segment 1 (Number of time quanta, between 1 to 16) */
    uint8_t tseg_2;                 /**< Timing segment 2 (Number of time quanta, 1 to 8) */
    uint8_t sjw;                    /**< Synchronization Jump Width (Max time quanta jump for synchronize from 1 to 4) */
    bool triple_sampling;           /**< Enables triple sampling when the TWAI controller samples a bit */
} twai_timing_config_t;

/**
 * @brief   Structure for acceptance filter configuration of the TWAI driver (see documentation)
 *
 * @note    Macro initializers are available for this structure
 */
typedef struct {
    uint32_t acceptance_code;       /**< 32-bit acceptance code */
    uint32_t acceptance_mask;       /**< 32-bit acceptance mask */
    bool single_filter;             /**< Use Single Filter Mode (see documentation) */
} twai_filter_config_t;