帮我用C写一段CANopen SDO函数

以下是一个简单的CANopen SDO函数的C代码示例：

#include <stdio.h>
#include <stdint.h>

// Define CANopen SDO command codes
#define SDO_READ_REQUEST 0x40
#define SDO_READ_RESPONSE 0x43
#define SDO_WRITE_REQUEST 0x23
#define SDO_WRITE_RESPONSE 0x60

// Define CANopen SDO error codes
#define SDO_NO_ERROR 0x0000
#define SDO_ACCESS_ERROR 0x0601
#define SDO_DATA_ERROR 0x0607
#define SDO_ABORTED_ERROR 0x0800

// Define CANopen SDO object dictionary entry structure
typedef struct {
    uint16_t index;
    uint8_t subindex;
    uint32_t value;
} SDO_Entry_t;

// Define CANopen SDO request message structure
typedef struct {
    uint8_t command;
    uint16_t index;
    uint8_t subindex;
    uint32_t data;
} SDO_Request_t;

// Define CANopen SDO response message structure
typedef struct {
    uint8_t command;
    uint16_t index;
    uint8_t subindex;
    uint16_t error;
    uint32_t data;
} SDO_Response_t;

// Function to send a CAN message with the specified ID and data
void CAN_SendMessage(uint32_t id, uint8_t* data, uint8_t length) {
    // Implementation not shown
}

// Function to receive a CAN message and return its ID, data, and length
void CAN_ReceiveMessage(uint32_t* id, uint8_t* data, uint8_t* length) {
    // Implementation not shown
}

// Function to read a CANopen SDO object dictionary entry
uint16_t CANopen_SDO_Read(SDO_Entry_t* entry) {
    // Construct SDO request message
    SDO_Request_t request;
    request.command = SDO_READ_REQUEST;
    request.index = entry->index;
    request.subindex = entry->subindex;
    request.data = 0;

    // Send SDO request message and wait for response
    CAN_SendMessage(0x600 + node_id, (uint8_t*)&request, sizeof(request));
    SDO_Response_t response;
    uint32_t id;
    uint8_t data[8];
    uint8_t length;
    do {
        CAN_ReceiveMessage(&id, data, &length);
    } while (id != 0x580 + node_id || length != sizeof(response) || ((SDO_Response_t*)data)->command != SDO_READ_RESPONSE);

    // Parse SDO response message and return error code
    response = *(SDO_Response_t*)data;
    if (response.error == SDO_NO_ERROR) {
        entry->value = response.data;
    }
    return response.error;
}

// Function to write a CANopen SDO object dictionary entry
uint16_t CANopen_SDO_Write(SDO_Entry_t* entry) {
    // Construct SDO request message
    SDO_Request_t request;
    request.command = SDO_WRITE_REQUEST;
    request.index = entry->index;
    request.subindex = entry->subindex;
    request.data = entry->value;

    // Send SDO request message and wait for response
    CAN_SendMessage(0x600 + node_id, (uint8_t*)&request, sizeof(request));
    SDO_Response_t response;
    uint32_t id;
    uint8_t data[8];
    uint8_t length;
    do {
        CAN_ReceiveMessage(&id, data, &length);
    } while (id != 0x580 + node_id || length != sizeof(response) || ((SDO_Response_t*)data)->command != SDO_WRITE_RESPONSE);

    // Parse SDO response message and return error code
    response = *(SDO_Response_t*)data;
    return response.error;
}

这个示例包含了一个CANopen SDO对象字典条目结构和两个函数，一个用于读取条目，另一个用于写入条目。这些函数都使用CAN总线来发送和接收CANopen SDO消息，并返回错误代码以指示操作的成功或失败。请注意，这个示例的实际实现可能需要根据您的特定应用程序进行修改。