周立功在发送报文的时候,是否自动在报文后面加了checksum?
时间: 2024-04-02 16:33:17 浏览: 17
周立功是TCP/IP协议的设计者之一,他在设计TCP/IP协议时确实考虑了校验的问题,并且在TCP协议段中加入了校验和的计算。在TCP的报文段中,有一个16位的校验和字段,用于检验TCP头部和数据的完整性。发送方在发送报文时会计算校验和,并将结果放入校验和字段中,接收方在接收到报文时也会计算校验和,并将计算结果与接收到的校验和进行比较,以判断报文是否有错。因此可以说,周立功在TCP协议设计中考虑了校验和的问题,并在报文中加入了校验和。
相关问题
VBA控制周立功CAN卡接收和发送报文代码
下面是一个使用VBA控制周立功CAN卡接收和发送报文的示例代码:
首先,要在代码中引用周立功CAN卡的API库文件,可以使用以下代码:
```
Private Declare Function OpenDevice Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long, ByVal Reserved As Long) As Long
Private Declare Function CloseDevice Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long) As Long
Private Declare Function InitCAN Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long, ByVal CANInd As Long, ByRef pInitConfig As CanInitConfig) As Long
Private Declare Function ReadCanMsg Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long, ByVal CANInd As Long, ByRef pCanMsg As CanMsg, ByVal Len As Long, ByVal WaitTime As Long) As Long
Private Declare Function Transmit Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long, ByVal CANInd As Long, ByRef pSend As CanMsg, ByVal Length As Long) As Long
```
然后,定义CAN卡的初始化配置和CAN消息结构体:
```
Type CanInitConfig
AccCode As Long
AccMask As Long
Reserved As Long
Filter As Byte
Timing0 As Byte
Timing1 As Byte
Mode As Byte
End Type
Type CanMsg
ID As Long
TimeStamp As Long
TimeFlag As Byte
SendType As Byte
RemoteFlag As Byte
ExternFlag As Byte
DataLen As Byte
Data(7) As Byte
Reserved As Long
End Type
```
接下来就是具体的发送和接收CAN消息的代码:
发送CAN消息:
```
Dim canMsg As CanMsg
canMsg.ID = 0x123
canMsg.DataLen = 8
canMsg.Data(0) = 0x11
canMsg.Data(1) = 0x22
canMsg.Data(2) = 0x33
canMsg.Data(3) = 0x44
canMsg.Data(4) = 0x55
canMsg.Data(5) = 0x66
canMsg.Data(6) = 0x77
canMsg.Data(7) = 0x88
Transmit 4, 0, 0, canMsg, 1
```
接收CAN消息:
```
Dim canMsg As CanMsg
ReadCanMsg 4, 0, 0, canMsg, 1, 100
Debug.Print "ID: " & canMsg.ID
Debug.Print "Data: " & canMsg.Data(0) & " " & canMsg.Data(1) & " " & canMsg.Data(2) & " " & canMsg.Data(3) & " " & canMsg.Data(4) & " " & canMsg.Data(5) & " " & canMsg.Data(6) & " " & canMsg.Data(7)
```
需要注意的是,在使用周立功CAN卡时,需要先打开设备并初始化CAN卡。完整的代码示例如下:
```
Private Declare Function OpenDevice Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long, ByVal Reserved As Long) As Long
Private Declare Function CloseDevice Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long) As Long
Private Declare Function InitCAN Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long, ByVal CANInd As Long, ByRef pInitConfig As CanInitConfig) As Long
Private Declare Function ReadCanMsg Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long, ByVal CANInd As Long, ByRef pCanMsg As CanMsg, ByVal Len As Long, ByVal WaitTime As Long) As Long
Private Declare Function Transmit Lib "ZLGCAN.dll" (ByVal DeviceType As Long, ByVal DeviceInd As Long, ByVal CANInd As Long, ByRef pSend As CanMsg, ByVal Length As Long) As Long
Type CanInitConfig
AccCode As Long
AccMask As Long
Reserved As Long
Filter As Byte
Timing0 As Byte
Timing1 As Byte
Mode As Byte
End Type
Type CanMsg
ID As Long
TimeStamp As Long
TimeFlag As Byte
SendType As Byte
RemoteFlag As Byte
ExternFlag As Byte
DataLen As Byte
Data(7) As Byte
Reserved As Long
End Type
Sub Test()
Dim initConfig As CanInitConfig
initConfig.AccCode = 0
initConfig.AccMask = &HFFFFFFFF
initConfig.Filter = 1
initConfig.Timing0 = &H1C
initConfig.Timing1 = &H1C
initConfig.Mode = 0
OpenDevice 4, 0, 0
InitCAN 4, 0, 0, initConfig
Dim canMsg As CanMsg
canMsg.ID = 0x123
canMsg.DataLen = 8
canMsg.Data(0) = 0x11
canMsg.Data(1) = 0x22
canMsg.Data(2) = 0x33
canMsg.Data(3) = 0x44
canMsg.Data(4) = 0x55
canMsg.Data(5) = 0x66
canMsg.Data(6) = 0x77
canMsg.Data(7) = 0x88
Transmit 4, 0, 0, canMsg, 1
ReadCanMsg 4, 0, 0, canMsg, 1, 100
Debug.Print "ID: " & canMsg.ID
Debug.Print "Data: " & canMsg.Data(0) & " " & canMsg.Data(1) & " " & canMsg.Data(2) & " " & canMsg.Data(3) & " " & canMsg.Data(4) & " " & canMsg.Data(5) & " " & canMsg.Data(6) & " " & canMsg.Data(7)
CloseDevice 4, 0
End Sub
```
python调用周立功接口函数,完成can报文的接收,usbcanfd200u版本
要使用周立功的接口函数来完成CAN报文的接收,需要先安装好周立功提供的驱动程序及API库,并且在Python中调用该API库。
以下是一个基本的Python代码示例,演示如何使用周立功的接口函数来实现CAN报文的接收:
```python
import os
from ctypes import *
# 加载周立功提供的API库
dll_path = os.path.join(os.getcwd(), "ControlCAN.dll")
can_lib = cdll.LoadLibrary(dll_path)
# 定义数据类型
DWORD = c_ulong
HANDLE = c_void_p
BYTE = c_ubyte
PVCI_CAN_OBJ = POINTER(VCI_CAN_OBJ)
# 定义CAN参数结构体
class VCI_INIT_CONFIG(Structure):
_fields_ = [("AccCode", DWORD),
("AccMask", DWORD),
("Reserved", DWORD),
("Filter", c_ubyte),
("Timing0", c_ubyte),
("Timing1", c_ubyte),
("Mode", c_ubyte)]
# 打开CAN设备
device_type = 4 # USB-CANFD-200U
device_index = 0
can_lib.VCI_OpenDevice(device_type, device_index, 0)
# 初始化CAN参数
can_config = VCI_INIT_CONFIG()
can_config.AccCode = 0x00000000
can_config.AccMask = 0xFFFFFFFF
can_config.Filter = 0x01
can_config.Timing0 = 0x01
can_config.Timing1 = 0x1C
can_config.Mode = 0x00
can_lib.VCI_InitCAN(device_type, device_index, 0, byref(can_config))
# 启动CAN设备
can_lib.VCI_StartCAN(device_type, device_index, 0)
# 循环读取CAN报文
while True:
# 读取CAN报文数量
count = can_lib.VCI_GetReceiveNum(device_type, device_index, 0)
if count > 0:
# 读取CAN报文数据
can_data = (VCI_CAN_OBJ * count)()
can_lib.VCI_Receive(device_type, device_index, 0, byref(can_data), count, 0)
# 处理CAN报文数据
for i in range(count):
can_msg = can_data[i]
print("ID: 0x{:08X}, Data: {}".format(can_msg.ID, can_msg.Data))
```
在上述代码中,我们首先加载了周立功提供的API库,并定义了一些需要使用的数据类型和CAN参数结构体。然后通过调用接口函数来打开、初始化和启动CAN设备。最后,在一个循环中不断读取CAN报文数据,并进行处理。
需要注意的是,由于周立功的API库是用C语言编写的,因此在Python中调用时需要使用ctypes库来进行包装和转换。此外,还需要根据实际情况修改CAN参数和设备编号等参数。
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