本篇文章介绍使用python来调用CAN通讯的DLL实现方法
由于工作上的需要，经常要与USBCAN打交道，但厂家一般不会提供PYTHON的例子，于是自己摸索地写一个例子出来，以便在工作上随时可以使用PYTHON来测试CAN的功能。
这里的例子是使用珠海创芯科技有限公司的USBCAN接口卡，他们提供一个ControlCAN.dll，也提供了一个.h文件，如下：
#ifndef CONTROLCAN_H
#define CONTROLCAN_H
////文件版本：v2.00 20150920
//#include <cvidef.h> //使用CVI平台开发，请使用该语句。
//接口卡类型定义
#define VCI_USBCAN1 3
#define VCI_USBCAN2 4
#define VCI_USBCAN2A 4
#define VCI_USBCAN_E_U 20
#define VCI_USBCAN_2E_U 21
//函数调用返回状态值
#define STATUS_OK 1
#define STATUS_ERR 0
/*------------------------------------------------兼容ZLG的函数及数据类型------------------------------------------------*/
//1.ZLGCAN系列接口卡信息的数据类型。
typedef struct _VCI_BOARD_INFO{
unsigned short hw_Version;
unsigned short fw_Version;
unsigned short dr_Version;
unsigned short in_Version;
unsigned short irq_Num;
unsigned char can_Num;
char str_Serial_Num[20];
char str_hw_Type[40];
unsigned short Reserved[4];
} VCI_BOARD_INFO,*PVCI_BOARD_INFO;
//2.定义CAN信息帧的数据类型。
typedef struct _VCI_CAN_OBJ{
unsigned int ID;
unsigned int TimeStamp;
unsigned char TimeFlag;
unsigned char SendType;
unsigned char RemoteFlag;//是否是远程帧
unsigned char ExternFlag;//是否是扩展帧
unsigned char DataLen;
unsigned char Data[8];
unsigned char Reserved[3];
}VCI_CAN_OBJ,*PVCI_CAN_OBJ;
//3.定义初始化CAN的数据类型
typedef struct _VCI_INIT_CONFIG{
unsigned long AccCode;
unsigned long AccMask;
unsigned long Reserved;
unsigned char Filter;
unsigned char Timing0;
unsigned char Timing1;
unsigned char Mode;
}VCI_INIT_CONFIG,*PVCI_INIT_CONFIG;
///////// new add struct for filter /////////
typedef struct _VCI_FILTER_RECORD{
unsigned long ExtFrame; //是否为扩展帧
unsigned long Start;
unsigned long End;
}VCI_FILTER_RECORD,*PVCI_FILTER_RECORD;
#define EXTERNC extern "C"
EXTERNC unsigned long __stdcall VCI_OpenDevice(unsigned long DeviceType,unsigned long DeviceInd,unsigned long Reserved);
EXTERNC unsigned long __stdcall VCI_CloseDevice(unsigned long DeviceType,unsigned long DeviceInd);
EXTERNC unsigned long __stdcall VCI_InitCAN(unsigned long DeviceType, unsigned long DeviceInd, unsigned long CANInd, PVCI_INIT_CONFIG pInitConfig);
EXTERNC unsigned long __stdcall VCI_ReadBoardInfo(unsigned long DeviceType,unsigned long DeviceInd,PVCI_BOARD_INFO pInfo);
EXTERNC unsigned long __stdcall VCI_SetReference(unsigned long DeviceType,unsigned long DeviceInd,unsigned long CANInd,unsigned long RefType,void* pData);
EXTERNC unsigned long __stdcall VCI_GetReceiveNum(unsigned long DeviceType,unsigned long DeviceInd,unsigned long CANInd);
EXTERNC unsigned long __stdcall VCI_ClearBuffer(unsigned long DeviceType,unsigned long DeviceInd,unsigned long CANInd);
EXTERNC unsigned long __stdcall VCI_StartCAN(unsigned long DeviceType,unsigned long DeviceInd,unsigned long CANInd);
EXTERNC unsigned long __stdcall VCI_ResetCAN(unsigned long DeviceType,unsigned long DeviceInd,unsigned long CANInd);
EXTERNC unsigned long __stdcall VCI_Transmit(unsigned long DeviceType,unsigned long DeviceInd,unsigned long CANInd,PVCI_CAN_OBJ pSend,unsigned long Len);
EXTERNC unsigned long __stdcall VCI_Receive(unsigned long DeviceType,unsigned long DeviceInd,unsigned long CANInd,PVCI_CAN_OBJ pReceive,unsigned long Len,int WaitTime);
/*------------------------------------------------其他补充函数及数据结构描述------------------------------------------------*/
//USB-CAN总线适配器板卡信息的数据类型1，该类型为VCI_FindUsbDevice函数的返回参数。
typedef struct _VCI_BOARD_INFO1{
unsigned long hw_Version;
unsigned long fw_Version;
unsigned long dr_Version;
unsigned long in_Version;
unsigned long irq_Num;
unsigned char can_Num;
unsigned char Reserved;
char str_Serial_Num[8];
char str_hw_Type[16];
char str_Usb_Serial[4][4];
} VCI_BOARD_INFO1,*PVCI_BOARD_INFO1;
//USB-CAN总线适配器板卡信息的数据类型2，该类型为VCI_FindUsbDevice函数的返回参数。为扩展更多的设备
typedef struct _VCI_BOARD_INFO2{
unsigned long hw_Version;
unsigned long fw_Version;
unsigned long dr_Version;
unsigned long in_Version;
unsigned long irq_Num;
unsigned char can_Num;
unsigned char Reserved;
char str_Serial_Num[8];
char str_hw_Type[16];
char str_Usb_Serial[10][4];
} VCI_BOARD_INFO2,*PVCI_BOARD_INFO2;
#define EXTERNC extern "C"
EXTERNC unsigned long __stdcall VCI_GetReference2(unsigned long DevType,unsigned long DevIndex,unsigned long CANIndex,unsigned long Reserved,unsigned char *pData);
EXTERNC unsigned long __stdcall VCI_SetReference2(unsigned long DevType,unsigned long DevIndex,unsigned long CANIndex,unsigned long RefType,unsigned char *pData);
EXTERNC unsigned long __stdcall VCI_ConnectDevice(unsigned long DevType,unsigned long DevIndex);
EXTERNC unsigned long __stdcall VCI_UsbDeviceReset(unsigned long DevType,unsigned long DevIndex,unsigned long Reserved);
EXTERNC unsigned long __stdcall VCI_FindUsbDevice(PVCI_BOARD_INFO1 pInfo);
EXTERNC unsigned long __stdcall VCI_FindUsbDevice2(PVCI_BOARD_INFO2 pInfo);
#endif
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要调用这些函数才可以完成工作，下面就来创建一个例子，从CAN的通道0向通道1来发送一帧CAN数据，例子代码如下：
#python3.6 32位
#https://blog.csdn.net/caimouse/article/details/51749579
#开发人员：蔡军生（QQ：9073204） 深圳 2018-3-25
#
from ctypes import *
VCI_USBCAN2A = 4
STATUS_OK = 1
class VCI_INIT_CONFIG(Structure):
_fields_ = [("AccCode", c_ulong),
("AccMask", c_ulong),
("Reserved", c_ulong),
("Filter", c_ubyte),
("Timing0", c_ubyte),
("Timing1", c_ubyte),
("Mode", c_ubyte)
]
class VCI_CAN_OBJ(Structure):
_fields_ = [("ID", c_uint),
("TimeStamp", c_uint),
("TimeFlag", c_ubyte),
("SendType", c_ubyte),
("RemoteFlag", c_ubyte),
("ExternFlag", c_ubyte),
("DataLen", c_ubyte),
("Data", c_ubyte*8),
("Reserved", c_ubyte*3)
]
CanDLLName = 'ControlCAN.dll' #DLL是32位的，必须使用32位的PYTHON
canDLL = windll.LoadLibrary(CanDLLName)
print(CanDLLName)
ret = canDLL.VCI_OpenDevice(VCI_USBCAN2A, 0, 0)
print(ret)
if ret != STATUS_OK:
print('调用 VCI_OpenDevice出错\r\n')
#初始0通道
vci_initconfig = VCI_INIT_CONFIG(0x80000008, 0xFFFFFFFF, 0,
2, 0x00, 0x1C, 0)
ret = canDLL.VCI_InitCAN(VCI_USBCAN2A, 0, 0, byref(vci_initconfig))
if ret != STATUS_OK:
print('调用 VCI_InitCAN出错\r\n')
ret = canDLL.VCI_StartCAN(VCI_USBCAN2A, 0, 0)
if ret != STATUS_OK:
print('调用 VCI_StartCAN出错\r\n')
#初始1通道
ret = canDLL.VCI_InitCAN(VCI_USBCAN2A, 0, 1, byref(vci_initconfig))
if ret != STATUS_OK:
print('调用 VCI_InitCAN 1 出错\r\n')
ret = canDLL.VCI_StartCAN(VCI_USBCAN2A, 0, 1)
if ret != STATUS_OK:
print('调用 VCI_StartCAN 1 出错\r\n')
#通道0发送数据
ubyte_array = c_ubyte*8
a = ubyte_array(1,2,3,4, 5, 6, 7, 64)
ubyte_3array = c_ubyte*3
b = ubyte_3array(0, 0 , 0)
vci_can_obj = VCI_CAN_OBJ(0x0, 0, 0, 1, 0, 0, 8, a, b)
ret = canDLL.VCI_Transmit(VCI_USBCAN2A, 0, 0, byref(vci_can_obj), 1)
if ret != STATUS_OK:
print('调用 VCI_Transmit 出错\r\n')
#通道1接收数据
a = ubyte_array(0, 0, 0, 0, 0, 0, 0, 0)
vci_can_obj = VCI_CAN_OBJ(0x0, 0, 0, 1, 0, 0, 8, a, b)
ret = canDLL.VCI_Receive(VCI_USBCAN2A, 0, 1, byref(vci_can_obj), 1, 0)
print(ret)
while ret <= 0:
print('调用 VCI_Receive 出错\r\n')
ret = canDLL.VCI_Receive(VCI_USBCAN2A, 0, 1, byref(vci_can_obj), 1, 0)
if ret > 0:
print(vci_can_obj.DataLen)
print(list(vci_can_obj.Data))
#关闭
canDLL.VCI_CloseDevice(VCI_USBCAN2A, 0)
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运行结果输出如下：
ControlCAN.dll
1
1
8
[1, 2, 3, 4, 5, 6, 7, 64]
可以看到从通道1里收通道0发过来的数据，达到这个程序的目的。
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