Chapter 157: CAN-FD Implementation on ESP32

#include <stdio.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/spi_master.h"
#include "driver/gpio.h"
#include "esp_log.h"

static const char *TAG = "CANFD_EXTERNAL";

// Define SPI host, pins (example for HSPI)
#define SPI_HOST HSPI_HOST // Or VSPI_HOST
#define PIN_NUM_MOSI 13
#define PIN_NUM_MISO 12
#define PIN_NUM_SCLK 14
#define PIN_NUM_CS   15
#define PIN_NUM_INT  4  // Example interrupt pin
// #define PIN_NUM_RESET 5 // Example reset pin

spi_device_handle_t spi_canfd_device;

// Hypothetical CAN-FD Controller Command/Register Defines
#define CANFD_CMD_WRITE_REG  0x02
#define CANFD_CMD_READ_REG   0x03
#define CANFD_REG_CONFIG     0x0A // Example configuration register address
#define CANFD_REG_TX_BUFFER  0x30 // Example TX buffer address
#define CANFD_REG_RX_BUFFER  0x40 // Example RX buffer address

// Initialize SPI bus and add the CAN-FD controller as a device
esp_err_t spi_init_canfd_controller(void) {
    esp_err_t ret;
    spi_bus_config_t buscfg = {
        .mosi_io_num = PIN_NUM_MOSI,
        .miso_io_num = PIN_NUM_MISO,
        .sclk_io_num = PIN_NUM_SCLK,
        .quadwp_io_num = -1, // Not used
        .quadhd_io_num = -1, // Not used
        .max_transfer_sz = 64 + 4 // Max CAN-FD payload + command/address bytes
    };

    spi_device_interface_config_t devcfg = {
        .clock_speed_hz = 10 * 1000 * 1000, // 10 MHz (check CAN-FD controller datasheet for max SPI speed)
        .mode = 0,                          // SPI mode 0 (CPOL=0, CPHA=0)
        .spics_io_num = PIN_NUM_CS,
        .queue_size = 7,                    // We want to be able to queue 7 transactions
        // .pre_cb = NULL, // Can be used to handle CS manually if needed
    };

    // Initialize the SPI bus
    ret = spi_bus_initialize(SPI_HOST, &buscfg, SPI_DMA_CH_AUTO);
    ESP_ERROR_CHECK(ret);
    if (ret != ESP_OK) return ret;

    // Attach the CAN-FD controller to the SPI bus
    ret = spi_bus_add_device(SPI_HOST, &devcfg, &spi_canfd_device);
    ESP_ERROR_CHECK(ret);
    if (ret != ESP_OK) return ret;
    
    ESP_LOGI(TAG, "SPI initialized and CAN-FD controller device added.");
    return ESP_OK;
}

// Conceptual function to write to a register on the external CAN-FD controller
esp_err_t canfd_controller_write_reg(uint16_t reg_addr, uint8_t *data, size_t len) {
    if (len == 0 || len > 8) { // Example: limit register write length for simplicity
        ESP_LOGE(TAG, "Invalid data length for register write.");
        return ESP_ERR_INVALID_ARG;
    }

    spi_transaction_t t;
    memset(&t, 0, sizeof(t));

    // Max 1 byte command, 2 bytes address, up to 'len' data bytes
    uint8_t tx_buffer[1 + 2 + len]; 
    tx_buffer[0] = CANFD_CMD_WRITE_REG;
    tx_buffer[1] = (reg_addr >> 8) & 0xFF; // High byte of address (assuming 16-bit addr)
    tx_buffer[2] = reg_addr & 0xFF;        // Low byte of address
    memcpy(&tx_buffer[3], data, len);

    t.length = (3 + len) * 8; // Length in bits
    t.tx_buffer = tx_buffer;
    t.rx_buffer = NULL;       // Not expecting data back for a write

    esp_err_t ret = spi_device_polling_transmit(spi_canfd_device, &t); // Or spi_device_transmit for interrupt driven
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "SPI transmit failed for register write: %s", esp_err_to_name(ret));
    }
    return ret;
}

// Conceptual function to read from a register
esp_err_t canfd_controller_read_reg(uint16_t reg_addr, uint8_t *rx_data, size_t len) {
    if (len == 0 || len > 8) {
        ESP_LOGE(TAG, "Invalid data length for register read.");
        return ESP_ERR_INVALID_ARG;
    }

    spi_transaction_t t;
    memset(&t, 0, sizeof(t));

    uint8_t tx_buffer[1 + 2]; // Command + Address
    tx_buffer[0] = CANFD_CMD_READ_REG;
    tx_buffer[1] = (reg_addr >> 8) & 0xFF;
    tx_buffer[2] = reg_addr & 0xFF;
    
    // For SPI read, we send command+address, then clock in data.
    // The total transaction length includes command, address, and expected data.
    // Some controllers might require dummy bytes after address during read.
    // This is highly dependent on the specific CAN-FD controller's SPI protocol.

    // Simplified: Assume command+address is sent, then 'len' bytes are read.
    // A common pattern is to send command+address, then send dummy bytes to clock in data.
    // For this example, we'll use a combined tx/rx buffer for simplicity,
    // though often tx is command/addr and rx is separate.
    
    uint8_t spi_tx_payload[3 + len]; // Cmd, Addr_H, Addr_L, Dummy bytes for read
    uint8_t spi_rx_payload[3 + len];
    memset(spi_tx_payload, 0, sizeof(spi_tx_payload)); // Important for dummy bytes

    spi_tx_payload[0] = CANFD_CMD_READ_REG;
    spi_tx_payload[1] = (reg_addr >> 8) & 0xFF;
    spi_tx_payload[2] = reg_addr & 0xFF;
    // The rest of spi_tx_payload are dummy bytes to clock in data

    t.length = (3 + len) * 8; // Total bits for command, address, and data to be read
    t.tx_buffer = spi_tx_payload;
    t.rx_buffer = spi_rx_payload;

    esp_err_t ret = spi_device_polling_transmit(spi_canfd_device, &t);
    if (ret == ESP_OK) {
        memcpy(rx_data, &spi_rx_payload[3], len); // Data starts after cmd+addr in rx_buffer
    } else {
        ESP_LOGE(TAG, "SPI transmit failed for register read: %s", esp_err_to_name(ret));
    }
    return ret;
}


void main_task(void *pvParameters) {
    ESP_ERROR_CHECK(spi_init_canfd_controller());

    // Example: Conceptual configuration write
    // This would involve multiple register writes based on CAN-FD IC datasheet
    // to set modes, bitrates (nominal and data), filters, etc.
    ESP_LOGI(TAG, "Conceptually configuring CAN-FD controller...");
    uint8_t config_data[] = {0x87}; // Example: Set CANFD mode with BRS, Normal Op Mode
                                    // (Actual value depends on specific controller)
    if (canfd_controller_write_reg(CANFD_REG_CONFIG, config_data, 1) == ESP_OK) {
        ESP_LOGI(TAG, "Conceptual config register write successful.");
    } else {
        ESP_LOGE(TAG, "Conceptual config register write failed.");
    }

    // Further operations (send/receive tasks) would go here...
    vTaskDelete(NULL);
}

void app_main(void) {
    xTaskCreate(main_task, "main_task", 4096, NULL, 5, NULL);
}

// Add to your main.c or a separate driver file

// Structure to hold CAN-FD message (conceptual)
typedef struct {
    uint32_t id;         // CAN ID (11-bit or 29-bit)
    bool is_extended_id; // true for 29-bit ID
    bool fdf;            // FD Format (must be true for CAN-FD)
    bool brs;            // Bit Rate Switch
    bool esi;            // Error State Indicator (usually false for TX)
    uint8_t dlc;         // Data Length Code (0-8, or 9-15 for 12-64 bytes)
    uint8_t data[64];
    uint8_t actual_len;  // Actual number of data bytes (0-64)
} canfd_frame_t;

// Map DLC values to actual byte counts for CAN-FD
uint8_t dlc_to_bytes_canfd(uint8_t dlc_val) {
    if (dlc_val <= 8) return dlc_val;
    switch (dlc_val) {
        case 9:  return 12;
        case 10: return 16;
        case 11: return 20;
        case 12: return 24;
        case 13: return 32;
        case 14: return 48;
        case 15: return 64;
        default: return 0; // Invalid DLC
    }
}

// Conceptual function to send a CAN-FD frame via external controller
esp_err_t canfd_transmit(canfd_frame_t *frame) {
    if (!frame->fdf) {
        ESP_LOGE(TAG, "Frame is not marked as CAN-FD (FDF=0)");
        return ESP_ERR_INVALID_ARG;
    }
    uint8_t actual_payload_bytes = dlc_to_bytes_canfd(frame->dlc);
    if (actual_payload_bytes == 0 && frame->dlc > 8) { // dlc_to_bytes_canfd returns 0 for invalid DLC > 8
         ESP_LOGE(TAG, "Invalid DLC for CAN-FD frame: %d", frame->dlc);
        return ESP_ERR_INVALID_ARG;
    }
    if (frame->actual_len != actual_payload_bytes) {
        ESP_LOGW(TAG, "Frame actual_len (%d) does not match DLC-derived bytes (%d). Using DLC-derived.", frame->actual_len, actual_payload_bytes);
        // Ensure actual_payload_bytes is used for SPI transfer length
    }


    ESP_LOGI(TAG, "Preparing to transmit CAN-FD frame: ID=0x%lX, DLC=%d (%d bytes), BRS=%d",
             frame->id, frame->dlc, actual_payload_bytes, frame->brs);

    // This is highly dependent on the external CAN-FD controller's architecture.
    // Typically involves:
    // 1. Finding an available TX buffer/message object.
    // 2. Formatting the ID, control flags (FDF, BRS, ESI), DLC according to controller's requirements.
    // 3. Writing the ID, control flags, DLC, and data payload to the controller's RAM via SPI.
    // 4. Setting a "transmit request" bit for that buffer/object.

    // Conceptual: Write to a specific TX buffer address (e.g., CANFD_REG_TX_BUFFER)
    // The buffer format in controller's RAM is IC-specific.
    // Example: [ID_Bytes(4), Control_Bytes(1-2), DLC_Byte(1), Data_Bytes(0-64)]

    uint8_t tx_spi_payload[4 + 2 + 1 + actual_payload_bytes]; // Max size
    int offset = 0;

    // ID (assuming 4 bytes for standard/extended, controller handles format)
    if (frame->is_extended_id) {
        tx_spi_payload[offset++] = (frame->id >> 24) & 0xFF; // Assuming controller specific format
        tx_spi_payload[offset++] = (frame->id >> 16) & 0xFF;
        tx_spi_payload[offset++] = (frame->id >> 8) & 0xFF;
        tx_spi_payload[offset++] = frame->id & 0xFF;
    } else { // Standard ID
        tx_spi_payload[offset++] = (frame->id >> 8) & 0xFF; // Assuming controller specific format
        tx_spi_payload[offset++] = frame->id & 0xFF;
        tx_spi_payload[offset++] = 0x00; // Placeholder for alignment or specific controller needs
        tx_spi_payload[offset++] = 0x00; // Placeholder
    }

    // Control byte(s) - highly IC-specific
    uint8_t ctrl_byte = 0;
    if (frame->fdf) ctrl_byte |= (1 << 7); // Example: FDF bit
    if (frame->brs) ctrl_byte |= (1 << 6); // Example: BRS bit
    if (frame->esi) ctrl_byte |= (1 << 5); // Example: ESI bit
    tx_spi_payload[offset++] = ctrl_byte;
    // Potentially another control byte for extended ID flag, etc.

    // DLC
    tx_spi_payload[offset++] = frame->dlc;

    // Data
    memcpy(&tx_spi_payload[offset], frame->data, actual_payload_bytes);
    offset += actual_payload_bytes;

    // Now, write this `tx_spi_payload` to the CAN-FD controller's TX buffer register
    // using a function similar to `canfd_controller_write_reg` but adapted for block writes.
    // Let's assume a command `CANFD_CMD_LOAD_TX_BUFFER = 0x05`
    // And the address `CANFD_REG_TX_BUFFER_0 = 0x0030` (for first TX buffer)
    
    uint8_t spi_command_payload[1 + 2 + offset]; // CMD + ADDR + data
    spi_command_payload[0] = 0x05; // Hypothetical "Load TX Buffer" command
    spi_command_payload[1] = (0x0030 >> 8) & 0xFF; // Address of TX buffer
    spi_command_payload[2] = 0x0030 & 0xFF;
    memcpy(&spi_command_payload[3], tx_spi_payload, offset);

    spi_transaction_t t;
    memset(&t, 0, sizeof(t));
    t.length = (3 + offset) * 8;
    t.tx_buffer = spi_command_payload;
    
    esp_err_t ret = spi_device_polling_transmit(spi_canfd_device, &t);
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "SPI transmit for CAN-FD frame load failed: %s", esp_err_to_name(ret));
        return ret;
    }

    // After loading, send a command to request transmission of that buffer
    // e.g., write to a transmit request register.
    // uint8_t tx_req_cmd[] = { CANFD_CMD_WRITE_REG, (TX_REQ_REG >> 8) & 0xFF, TX_REQ_REG & 0xFF, 0x01 /* Request TX for buffer 0 */};
    // ... send this command ...
    
    ESP_LOGI(TAG, "CAN-FD frame conceptually loaded to external controller's TX buffer.");
    // Actual transmission request command would follow.
    return ESP_OK;
}

// In main_task, after configuration:
// canfd_frame_t my_fd_frame;
// my_fd_frame.id = 0x123;
// my_fd_frame.is_extended_id = false;
// my_fd_frame.fdf = true;
// my_fd_frame.brs = true; // Enable bit rate switching
// my_fd_frame.esi = false;
// my_fd_frame.dlc = 15; // Corresponds to 64 bytes
// my_fd_frame.actual_len = 64;
// for (int i = 0; i < my_fd_frame.actual_len; i++) {
//     my_fd_frame.data[i] = i;
// }
// canfd_transmit(&my_fd_frame);

// Add to your main.c

// GPIO interrupt handler
static void IRAM_ATTR canfd_rx_interrupt_handler(void *arg) {
    // In a real scenario, you'd signal a task from here.
    // For simplicity, just log (not recommended for production ISRs).
    // ets_printf("CAN-FD RX Interrupt!\n");
    // BaseType_t xHigherPriorityTaskWoken = pdFALSE;
    // vTaskNotifyGiveFromISR(can_rx_task_handle, &xHigherPriorityTaskWoken);
    // portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
    // For this example, we'll assume a global flag or similar simple mechanism
    // that a polling task would check. A task notification is better.
    gpio_intr_disable(PIN_NUM_INT); // Disable until processed
    // Signal a task to process the received frame
}

// Function to initialize GPIO interrupt for CAN-FD RX
void canfd_rx_interrupt_init(void) {
    gpio_config_t io_conf;
    io_conf.intr_type = GPIO_INTR_NEGEDGE; // Or as specified by CAN-FD controller
    io_conf.pin_bit_mask = (1ULL << PIN_NUM_INT);
    io_conf.mode = GPIO_MODE_INPUT;
    io_conf.pull_up_en = GPIO_PULLUP_ENABLE; // Or PULLDOWN_DISABLE, check controller datasheet
    gpio_config(&io_conf);

    gpio_install_isr_service(0); // ESP_INTR_FLAG_DEFAULT
    gpio_isr_handler_add(PIN_NUM_INT, canfd_rx_interrupt_handler, (void *)PIN_NUM_INT);
    ESP_LOGI(TAG, "CAN-FD RX interrupt initialized for GPIO %d", PIN_NUM_INT);
}

// Conceptual function to read a received CAN-FD frame
esp_err_t canfd_receive(canfd_frame_t *frame) {
    // This function would be called by a task after being signaled by the ISR.
    // 1. Check interrupt status registers on CAN-FD controller (via SPI read)
    //    to confirm a message is in an RX buffer and identify which one.
    // 2. Read the frame (ID, control, DLC, data) from the controller's RAM via SPI.
    //    Similar to canfd_transmit but using read commands and targeting RX buffer address.

    ESP_LOGI(TAG, "Attempting to read received CAN-FD frame...");
    
    // Conceptual: Read from a specific RX buffer (e.g., CANFD_REG_RX_BUFFER_0 = 0x0040)
    // The buffer format in controller's RAM is IC-specific.
    // Example: [ID_Bytes(4), Control_Bytes(1-2), DLC_Byte(1), Data_Bytes(0-64)]
    
    uint8_t spi_rx_buffer[4 + 2 + 1 + 64]; // Max size for frame data from controller
    // Assuming a command `CANFD_CMD_READ_RX_BUFFER = 0x06`
    // And address `CANFD_REG_RX_BUFFER_0 = 0x0040`

    uint8_t spi_tx_cmd_addr[3];
    spi_tx_cmd_addr[0] = 0x06; // Hypothetical "Read RX Buffer" command
    spi_tx_cmd_addr[1] = (0x0040 >> 8) & 0xFF; // Address of RX buffer
    spi_tx_cmd_addr[2] = 0x0040 & 0xFF;

    spi_transaction_t t;
    memset(&t, 0, sizeof(t));
    // We send command+address, then receive the buffer content
    // The total length is tricky: some controllers auto-send, others need dummy clocks.
    // Assume controller sends 'N' bytes after receiving command+address.
    // For simplicity, let's assume we read a fixed max size and then parse.
    // A better way is to first read a status/header register that gives the DLC of received frame.

    // Simplified: Read a fixed chunk that should contain the frame
    t.length = (3 + sizeof(spi_rx_buffer)) * 8; // Send 3 bytes, receive up to sizeof(spi_rx_buffer)
    t.tx_buffer = spi_tx_cmd_addr;              // Send command and address
    t.rxlength = sizeof(spi_rx_buffer) * 8;     // Expect to receive this many bytes of data
    t.rx_buffer = spi_rx_buffer;                // Buffer to store received data

    // This transaction structure is simplified. A real SPI read often involves sending the command
    // and address, then sending dummy bytes to clock in the response.
    // The `spi_device_transmit` can be used with `rx_buffer` set to get data back.
    // Or `spi_device_transfer` for full duplex.
    // Let's use a more common pattern for reading after sending command+address:
    
    uint8_t command_and_address[3] = {0x06, (0x0040 >> 8) & 0xFF, 0x0040 & 0xFF};
    uint8_t received_data_from_spi[sizeof(spi_rx_buffer)]; // Buffer for data part only

    // Transaction to send command and address
    spi_transaction_t t_cmd_addr = {
        .length = 3 * 8,
        .tx_buffer = command_and_address,
    };
    esp_err_t ret = spi_device_polling_transmit(spi_canfd_device, &t_cmd_addr);
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "SPI send command/address for RX failed: %s", esp_err_to_name(ret));
        return ret;
    }

    // Transaction to read the data (assuming controller now sends it)
    // The number of bytes to read should ideally be known from a status register or interrupt flags.
    // For now, assume we read a fixed number of bytes (e.g., 10 bytes for header + few data bytes)
    // or the max possible (and then parse DLC from it).
    // Let's assume we first read a header (e.g. 8 bytes: ID, control, DLC)
    uint8_t frame_header_from_spi[8];
    spi_transaction_t t_read_data = {
        .length = 8 * 8, // Read 8 bytes for header
        .rx_buffer = frame_header_from_spi,
    };
    ret = spi_device_polling_transmit(spi_canfd_device, &t_read_data); // Send dummy clocks, receive data
     if (ret != ESP_OK) {
        ESP_LOGE(TAG, "SPI read frame header failed: %s", esp_err_to_name(ret));
        return ret;
    }

    // Parse frame_header_from_spi to get ID, DLC, FDF, BRS, ESI
    // Example parsing (highly IC-specific):
    // frame->id = (frame_header_from_spi[0] << 24) | ... ; // Assuming 4 bytes for ID
    // uint8_t ctrl_byte = frame_header_from_spi[4];
    // frame->fdf = (ctrl_byte >> 7) & 0x01;
    // frame->brs = (ctrl_byte >> 6) & 0x01;
    // frame->esi = (ctrl_byte >> 5) & 0x01;
    // frame->dlc = frame_header_from_spi[5];
    // frame->actual_len = dlc_to_bytes_canfd(frame->dlc);

    // Then, if frame->actual_len > 0, perform another SPI read for the data bytes.
    // spi_transaction_t t_read_payload = {
    //    .length = frame->actual_len * 8,
    //    .rx_buffer = frame->data,
    // };
    // ret = spi_device_polling_transmit(spi_canfd_device, &t_read_payload);
    // ...

    // After successfully reading and parsing:
    // Clear interrupt flags on the CAN-FD controller (via SPI write).
    // Re-enable GPIO interrupt: gpio_intr_enable(PIN_NUM_INT);

    ESP_LOGI(TAG, "CAN-FD frame conceptually read. ID:0x%lX, DLC:%d, Data[0]:0x%02X",
             frame->id, frame->dlc, frame->data[0]); // Assuming frame populated
    return ESP_OK;
}

// In main_task or a dedicated RX task:
// canfd_rx_interrupt_init();
// while(1) {
//    // Wait for notification from ISR
//    // if (ulTaskNotifyTake(pdTRUE, portMAX_DELAY)) {
//    //    canfd_frame_t received_frame;
//    //    if (canfd_receive(&received_frame) == ESP_OK) {
//    //       // Process received_frame
//    //    }
//    //    gpio_intr_enable(PIN_NUM_INT); // Re-enable after processing
//    // }
//    vTaskDelay(pdMS_TO_TICKS(10)); // Polling if not using task notification
// }